[PATCH v5 0/8] Handle forwarded level-triggered interrupts

[PATCH v5 0/8] Handle forwarded level-triggered interrupts

[Christoffer Dall]

This series illustrates an alternative approach to Eric Auger's direct
EOI setup patches [1] in terms of the KVM VGIC support.

The idea is to maintain existing semantics for the VGIC for mapped
level-triggered IRQs and also support the timer using mapped IRQs with
the same VGIC support as VFIO interrupts.

Based on kvm-arm-gicv4-for-v4.15 (latest pull request of KVM/ARM changes
to the KVM tree).

Also available at:
git://git.kernel.org/pub/scm/linux/kernel/git/cdall/linux.git level-mapped-v5

(Apologies for sending this out during the merge window, but I've been
sitting on these for a while, and the VHE optimization patches have
gotten a fair amount of review lately, and I'd like to base the next
version on these patches.)

Changes since v4:
 - Rebased on the timer optimization series merged in the v4.15 merge
   window, which caused a fair amount of modifications to patch 3.
 - Added a static key to disable the sync operations when no VMs are
   using userspace irqchips to further optimize the performance
 - Fixed extra semicolon in vgic-mmio.c
 - Added commentary as requested during review
 - Dropped what was patch 4, because it was merged as part of GICv4
   support.
 - Factored out the VGIC input level function change as separate patch
   (helps bisect and debugging), before providing a function for the
   timer.

Changes since v3:
 - Added a number of patches and moved patches around a bit.
 - Check for uaccesses in the mmio handler functions
 - Fixed bugs in the mmio handler functions

Changes since v2:
 - Removed patch 5 from v2 and integrating the changes in what's now
   patch 5 to make it easier to reuse code when adding VFIO integration.
 - Changed the virtual distributor MMIO handling to use the
   pending_latch and more closely match the semantics of SPENDR and
   CPENDR for both level and edge mapped interrupts.

Changes since v1:
 - Added necessary changes to the timer (Patch 1)
 - Added handling of guest MMIO accesses to the virtual distributor
   (Patch 4)
 - Addressed Marc's comments from the initial RFC (mostly renames)

Thanks,
-Christoffer

Christoffer Dall (8):
  KVM: arm/arm64: Remove redundant preemptible checks
  KVM: arm/arm64: Factor out functionality to get vgic mmio
    requester_vcpu
  KVM: arm/arm64: Don't cache the timer IRQ level
  KVM: arm/arm64: vgic: Support level-triggered mapped interrupts
  KVM: arm/arm64: Support a vgic interrupt line level sample function
  KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs
  KVM: arm/arm64: Provide a get_input_level for the arch timer
  KVM: arm/arm64: Avoid work when userspace iqchips are not used

 include/kvm/arm_arch_timer.h  |   2 +
 include/kvm/arm_vgic.h        |  13 ++++-
 virt/kvm/arm/arch_timer.c     | 106 ++++++++++++++++++++++-----------------
 virt/kvm/arm/arm.c            |   2 -
 virt/kvm/arm/vgic/vgic-mmio.c | 114 ++++++++++++++++++++++++++++++++++--------
 virt/kvm/arm/vgic/vgic-v2.c   |  29 +++++++++++
 virt/kvm/arm/vgic/vgic-v3.c   |  29 +++++++++++
 virt/kvm/arm/vgic/vgic.c      |  42 ++++++++++++++--
 virt/kvm/arm/vgic/vgic.h      |   8 +++
 9 files changed, 270 insertions(+), 75 deletions(-)

-- 
2.14.2

[PATCH v5 0/8] Handle forwarded level-triggered interrupts

[Christoffer Dall]

This series illustrates an alternative approach to Eric Auger's direct
EOI setup patches [1] in terms of the KVM VGIC support.

The idea is to maintain existing semantics for the VGIC for mapped
level-triggered IRQs and also support the timer using mapped IRQs with
the same VGIC support as VFIO interrupts.

Based on kvm-arm-gicv4-for-v4.15 (latest pull request of KVM/ARM changes
to the KVM tree).

Also available at:
git://git.kernel.org/pub/scm/linux/kernel/git/cdall/linux.git level-mapped-v5

(Apologies for sending this out during the merge window, but I've been
sitting on these for a while, and the VHE optimization patches have
gotten a fair amount of review lately, and I'd like to base the next
version on these patches.)

Changes since v4:
 - Rebased on the timer optimization series merged in the v4.15 merge
   window, which caused a fair amount of modifications to patch 3.
 - Added a static key to disable the sync operations when no VMs are
   using userspace irqchips to further optimize the performance
 - Fixed extra semicolon in vgic-mmio.c
 - Added commentary as requested during review
 - Dropped what was patch 4, because it was merged as part of GICv4
   support.
 - Factored out the VGIC input level function change as separate patch
   (helps bisect and debugging), before providing a function for the
   timer.

Changes since v3:
 - Added a number of patches and moved patches around a bit.
 - Check for uaccesses in the mmio handler functions
 - Fixed bugs in the mmio handler functions

Changes since v2:
 - Removed patch 5 from v2 and integrating the changes in what's now
   patch 5 to make it easier to reuse code when adding VFIO integration.
 - Changed the virtual distributor MMIO handling to use the
   pending_latch and more closely match the semantics of SPENDR and
   CPENDR for both level and edge mapped interrupts.

Changes since v1:
 - Added necessary changes to the timer (Patch 1)
 - Added handling of guest MMIO accesses to the virtual distributor
   (Patch 4)
 - Addressed Marc's comments from the initial RFC (mostly renames)

Thanks,
-Christoffer

Christoffer Dall (8):
  KVM: arm/arm64: Remove redundant preemptible checks
  KVM: arm/arm64: Factor out functionality to get vgic mmio
    requester_vcpu
  KVM: arm/arm64: Don't cache the timer IRQ level
  KVM: arm/arm64: vgic: Support level-triggered mapped interrupts
  KVM: arm/arm64: Support a vgic interrupt line level sample function
  KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs
  KVM: arm/arm64: Provide a get_input_level for the arch timer
  KVM: arm/arm64: Avoid work when userspace iqchips are not used

 include/kvm/arm_arch_timer.h  |   2 +
 include/kvm/arm_vgic.h        |  13 ++++-
 virt/kvm/arm/arch_timer.c     | 106 ++++++++++++++++++++++-----------------
 virt/kvm/arm/arm.c            |   2 -
 virt/kvm/arm/vgic/vgic-mmio.c | 114 ++++++++++++++++++++++++++++++++++--------
 virt/kvm/arm/vgic/vgic-v2.c   |  29 +++++++++++
 virt/kvm/arm/vgic/vgic-v3.c   |  29 +++++++++++
 virt/kvm/arm/vgic/vgic.c      |  42 ++++++++++++++--
 virt/kvm/arm/vgic/vgic.h      |   8 +++
 9 files changed, 270 insertions(+), 75 deletions(-)

-- 
2.14.2

[PATCH v5 1/8] KVM: arm/arm64: Remove redundant preemptible checks

[Christoffer Dall]

The __this_cpu_read() and __this_cpu_write() functions already implement
checks for the required preemption levels when using
CONFIG_DEBUG_PREEMPT which gives you nice error messages and such.
Therefore there is no need to explicitly check this using a BUG_ON() in
the code (which we don't do for other uses of per cpu variables either).

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arm.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index c13d74c083fe..28548aeaf164 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -71,7 +71,6 @@ static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
 
 static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
 {
-	BUG_ON(preemptible());
 	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
 }
 
@@ -81,7 +80,6 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
  */
 struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
 {
-	BUG_ON(preemptible());
 	return __this_cpu_read(kvm_arm_running_vcpu);
 }
 
-- 
2.14.2

[PATCH v5 1/8] KVM: arm/arm64: Remove redundant preemptible checks

[Christoffer Dall]

The __this_cpu_read() and __this_cpu_write() functions already implement
checks for the required preemption levels when using
CONFIG_DEBUG_PREEMPT which gives you nice error messages and such.
Therefore there is no need to explicitly check this using a BUG_ON() in
the code (which we don't do for other uses of per cpu variables either).

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arm.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index c13d74c083fe..28548aeaf164 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -71,7 +71,6 @@ static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
 
 static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
 {
-	BUG_ON(preemptible());
 	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
 }
 
@@ -81,7 +80,6 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
  */
 struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
 {
-	BUG_ON(preemptible());
 	return __this_cpu_read(kvm_arm_running_vcpu);
 }
 
-- 
2.14.2

[PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Christoffer Dall]

We are about to distinguish between userspace accesses and mmio traps
for a number of the mmio handlers.  When the requester vcpu is NULL, it
mens we are handling a userspace acccess.

Factor out the functionality to get the request vcpu into its own
function, mostly so we have a common place to document the semantics of
the return value.

Also take the chance to move the functionality outside of holding a
spinlock and instead explicitly disable and enable preemption.  This
supports PREEMPT_RT kernels as well.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index deb51ee16a3d..6113cf850f47 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 	return value;
 }
 
+/*
+ * This function will return the VCPU that performed the MMIO access and
+ * trapped from twithin the VM, and will return NULL if this is a userspace
+ * access.
+ *
+ * We can disable preemption locally around accessing the per-CPU variable
+ * because even if the current thread is migrated to another CPU, reading the
+ * per-CPU value later will give us the same value as we update the per-CPU
+ * variable in the preempt notifier handlers.
+ */
+static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
+{
+	struct kvm_vcpu *vcpu;
+
+	preempt_disable();
+	vcpu = kvm_arm_get_running_vcpu();
+	preempt_enable();
+	return vcpu;
+}
+
 void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
@@ -184,24 +204,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
 static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 				    bool new_active_state)
 {
-	struct kvm_vcpu *requester_vcpu;
 	unsigned long flags;
-	spin_lock_irqsave(&irq->irq_lock, flags);
+	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
 
-	/*
-	 * The vcpu parameter here can mean multiple things depending on how
-	 * this function is called; when handling a trap from the kernel it
-	 * depends on the GIC version, and these functions are also called as
-	 * part of save/restore from userspace.
-	 *
-	 * Therefore, we have to figure out the requester in a reliable way.
-	 *
-	 * When accessing VGIC state from user space, the requester_vcpu is
-	 * NULL, which is fine, because we guarantee that no VCPUs are running
-	 * when accessing VGIC state from user space so irq->vcpu->cpu is
-	 * always -1.
-	 */
-	requester_vcpu = kvm_arm_get_running_vcpu();
+	spin_lock_irqsave(&irq->irq_lock, flags);
 
 	/*
 	 * If this virtual IRQ was written into a list register, we
@@ -213,6 +219,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	 * vgic_change_active_prepare)  and still has to sync back this IRQ,
 	 * so we release and re-acquire the spin_lock to let the other thread
 	 * sync back the IRQ.
+	 *
+	 * When accessing VGIC state from user space, requester_vcpu is
+	 * NULL, which is fine, because we guarantee that no VCPUs are running
+	 * when accessing VGIC state from user space so irq->vcpu->cpu is
+	 * always -1.
 	 */
 	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
 	       irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
-- 
2.14.2

[PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Christoffer Dall]

We are about to distinguish between userspace accesses and mmio traps
for a number of the mmio handlers.  When the requester vcpu is NULL, it
mens we are handling a userspace acccess.

Factor out the functionality to get the request vcpu into its own
function, mostly so we have a common place to document the semantics of
the return value.

Also take the chance to move the functionality outside of holding a
spinlock and instead explicitly disable and enable preemption.  This
supports PREEMPT_RT kernels as well.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index deb51ee16a3d..6113cf850f47 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
 	return value;
 }
 
+/*
+ * This function will return the VCPU that performed the MMIO access and
+ * trapped from twithin the VM, and will return NULL if this is a userspace
+ * access.
+ *
+ * We can disable preemption locally around accessing the per-CPU variable
+ * because even if the current thread is migrated to another CPU, reading the
+ * per-CPU value later will give us the same value as we update the per-CPU
+ * variable in the preempt notifier handlers.
+ */
+static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
+{
+	struct kvm_vcpu *vcpu;
+
+	preempt_disable();
+	vcpu = kvm_arm_get_running_vcpu();
+	preempt_enable();
+	return vcpu;
+}
+
 void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
@@ -184,24 +204,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
 static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 				    bool new_active_state)
 {
-	struct kvm_vcpu *requester_vcpu;
 	unsigned long flags;
-	spin_lock_irqsave(&irq->irq_lock, flags);
+	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
 
-	/*
-	 * The vcpu parameter here can mean multiple things depending on how
-	 * this function is called; when handling a trap from the kernel it
-	 * depends on the GIC version, and these functions are also called as
-	 * part of save/restore from userspace.
-	 *
-	 * Therefore, we have to figure out the requester in a reliable way.
-	 *
-	 * When accessing VGIC state from user space, the requester_vcpu is
-	 * NULL, which is fine, because we guarantee that no VCPUs are running
-	 * when accessing VGIC state from user space so irq->vcpu->cpu is
-	 * always -1.
-	 */
-	requester_vcpu = kvm_arm_get_running_vcpu();
+	spin_lock_irqsave(&irq->irq_lock, flags);
 
 	/*
 	 * If this virtual IRQ was written into a list register, we
@@ -213,6 +219,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	 * vgic_change_active_prepare)  and still has to sync back this IRQ,
 	 * so we release and re-acquire the spin_lock to let the other thread
 	 * sync back the IRQ.
+	 *
+	 * When accessing VGIC state from user space, requester_vcpu is
+	 * NULL, which is fine, because we guarantee that no VCPUs are running
+	 * when accessing VGIC state from user space so irq->vcpu->cpu is
+	 * always -1.
 	 */
 	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
 	       irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
-- 
2.14.2

[PATCH v5 3/8] KVM: arm/arm64: Don't cache the timer IRQ level

[Christoffer Dall]

The timer was modeled after a strict idea of modelling an interrupt line
level in software, meaning that only transitions in the level needed to
be reported to the VGIC.  This works well for the timer, because the
arch timer code is in complete control of the device and can track the
transitions of the line.

However, as we are about to support using the HW bit in the VGIC not
just for the timer, but also for VFIO which cannot track transitions of
the interrupt line, we have to decide on an interface for level
triggered mapped interrupts to the GIC, which both the timer and VFIO
can use.

VFIO only sees an asserting transition of the physical interrupt line,
and tells the VGIC when that happens.  That means that part of the
interrupt flow is offloaded to the hardware.

To use the same interface for VFIO devices and the timer, we therefore
have to change the timer (we cannot change VFIO because it doesn't know
the details of the device it is assigning to a VM).

Luckily, changing the timer is simple, we just need to stop 'caching'
the line level, but instead let the VGIC know the state of the timer
every time there is a potential change in the line level, and when the
line level should be asserted from the timer ISR.  The VGIC can ignore
extra notifications using its validate mechanism.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arch_timer.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 190c99ed1b73..5f8ad8e3f3ff 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -99,11 +99,9 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
 	}
 	vtimer = vcpu_vtimer(vcpu);
 
-	if (!vtimer->irq.level) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		if (kvm_timer_irq_can_fire(vtimer))
-			kvm_timer_update_irq(vcpu, true, vtimer);
-	}
+	vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+	if (kvm_timer_irq_can_fire(vtimer))
+		kvm_timer_update_irq(vcpu, true, vtimer);
 
 	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		kvm_vtimer_update_mask_user(vcpu);
@@ -324,12 +322,20 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+	bool level;
 
 	if (unlikely(!timer->enabled))
 		return;
 
-	if (kvm_timer_should_fire(vtimer) != vtimer->irq.level)
-		kvm_timer_update_irq(vcpu, !vtimer->irq.level, vtimer);
+	/*
+	 * The vtimer virtual interrupt is a 'mapped' interrupt, meaning part
+	 * of its lifecycle is offloaded to the hardware, and we therefore may
+	 * not have lowered the irq.level value before having to signal a new
+	 * interrupt, but have to signal an interrupt every time the level is
+	 * asserted.
+	 */
+	level = kvm_timer_should_fire(vtimer);
+	kvm_timer_update_irq(vcpu, level, vtimer);
 
 	if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
 		kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);
-- 
2.14.2

[PATCH v5 3/8] KVM: arm/arm64: Don't cache the timer IRQ level

[Christoffer Dall]

The timer was modeled after a strict idea of modelling an interrupt line
level in software, meaning that only transitions in the level needed to
be reported to the VGIC.  This works well for the timer, because the
arch timer code is in complete control of the device and can track the
transitions of the line.

However, as we are about to support using the HW bit in the VGIC not
just for the timer, but also for VFIO which cannot track transitions of
the interrupt line, we have to decide on an interface for level
triggered mapped interrupts to the GIC, which both the timer and VFIO
can use.

VFIO only sees an asserting transition of the physical interrupt line,
and tells the VGIC when that happens.  That means that part of the
interrupt flow is offloaded to the hardware.

To use the same interface for VFIO devices and the timer, we therefore
have to change the timer (we cannot change VFIO because it doesn't know
the details of the device it is assigning to a VM).

Luckily, changing the timer is simple, we just need to stop 'caching'
the line level, but instead let the VGIC know the state of the timer
every time there is a potential change in the line level, and when the
line level should be asserted from the timer ISR.  The VGIC can ignore
extra notifications using its validate mechanism.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arch_timer.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 190c99ed1b73..5f8ad8e3f3ff 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -99,11 +99,9 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
 	}
 	vtimer = vcpu_vtimer(vcpu);
 
-	if (!vtimer->irq.level) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		if (kvm_timer_irq_can_fire(vtimer))
-			kvm_timer_update_irq(vcpu, true, vtimer);
-	}
+	vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+	if (kvm_timer_irq_can_fire(vtimer))
+		kvm_timer_update_irq(vcpu, true, vtimer);
 
 	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		kvm_vtimer_update_mask_user(vcpu);
@@ -324,12 +322,20 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+	bool level;
 
 	if (unlikely(!timer->enabled))
 		return;
 
-	if (kvm_timer_should_fire(vtimer) != vtimer->irq.level)
-		kvm_timer_update_irq(vcpu, !vtimer->irq.level, vtimer);
+	/*
+	 * The vtimer virtual interrupt is a 'mapped' interrupt, meaning part
+	 * of its lifecycle is offloaded to the hardware, and we therefore may
+	 * not have lowered the irq.level value before having to signal a new
+	 * interrupt, but have to signal an interrupt every time the level is
+	 * asserted.
+	 */
+	level = kvm_timer_should_fire(vtimer);
+	kvm_timer_update_irq(vcpu, level, vtimer);
 
 	if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
 		kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);
-- 
2.14.2

[PATCH v5 4/8] KVM: arm/arm64: vgic: Support level-triggered mapped interrupts

[Christoffer Dall]

Level-triggered mapped IRQs are special because we only observe rising
edges as input to the VGIC, and we don't set the EOI flag and therefore
are not told when the level goes down, so that we can re-queue a new
interrupt when the level goes up.

One way to solve this problem is to side-step the logic of the VGIC and
special case the validation in the injection path, but it has the
unfortunate drawback of having to peak into the physical GIC state
whenever we want to know if the interrupt is pending on the virtual
distributor.

Instead, we can maintain the current semantics of a level triggered
interrupt by sort of treating it as an edge-triggered interrupt,
following from the fact that we only observe an asserting edge.  This
requires us to be a bit careful when populating the LRs and when folding
the state back in though:

 * We lower the line level when populating the LR, so that when
   subsequently observing an asserting edge, the VGIC will do the right
   thing.

 * If the guest never acked the interrupt while running (for example if
   it had masked interrupts at the CPU level while running), we have
   to preserve the pending state of the LR and move it back to the
   line_level field of the struct irq when folding LR state.

   If the guest never acked the interrupt while running, but changed the
   device state and lowered the line (again with interrupts masked) then
   we need to observe this change in the line_level.

   Both of the above situations are solved by sampling the physical line
   and set the line level when folding the LR back.

 * Finally, if the guest never acked the interrupt while running and
   sampling the line reveals that the device state has changed and the
   line has been lowered, we must clear the physical active state, since
   we will otherwise never be told when the interrupt becomes asserted
   again.

This has the added benefit of making the timer optimization patches
(https://lists.cs.columbia.edu/pipermail/kvmarm/2017-July/026343.html) a
bit simpler, because the timer code doesn't have to clear the active
state on the sync anymore.  It also potentially improves the performance
of the timer implementation because the GIC knows the state or the LR
and only needs to clear the
active state when the pending bit in the LR is still set, where the
timer has to always clear it when returning from running the guest with
an injected timer interrupt.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-v2.c | 29 +++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic-v3.c | 29 +++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic.c    | 23 +++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic.h    |  7 +++++++
 4 files changed, 88 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index 80897102da26..c32d7b93ffd1 100644
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -105,6 +105,26 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 				irq->pending_latch = false;
 		}
 
+		/*
+		 * Level-triggered mapped IRQs are special because we only
+		 * observe rising edges as input to the VGIC.
+		 *
+		 * If the guest never acked the interrupt we have to sample
+		 * the physical line and set the line level, because the
+		 * device state could have changed or we simply need to
+		 * process the still pending interrupt later.
+		 *
+		 * If this causes us to lower the level, we have to also clear
+		 * the physical active state, since we will otherwise never be
+		 * told when the interrupt becomes asserted again.
+		 */
+		if (vgic_irq_is_mapped_level(irq) && (val & GICH_LR_PENDING_BIT)) {
+			irq->line_level = vgic_get_phys_line_level(irq);
+
+			if (!irq->line_level)
+				vgic_irq_set_phys_active(irq, false);
+		}
+
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
@@ -162,6 +182,15 @@ void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
 			val |= GICH_LR_EOI;
 	}
 
+	/*
+	 * Level-triggered mapped IRQs are special because we only observe
+	 * rising edges as input to the VGIC.  We therefore lower the line
+	 * level here, so that we can take new virtual IRQs.  See
+	 * vgic_v2_fold_lr_state for more info.
+	 */
+	if (vgic_irq_is_mapped_level(irq) && (val & GICH_LR_PENDING_BIT))
+		irq->line_level = false;
+
 	/* The GICv2 LR only holds five bits of priority. */
 	val |= (irq->priority >> 3) << GICH_LR_PRIORITY_SHIFT;
 
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index f47e8481fa45..6b329414e57a 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -96,6 +96,26 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 				irq->pending_latch = false;
 		}
 
+		/*
+		 * Level-triggered mapped IRQs are special because we only
+		 * observe rising edges as input to the VGIC.
+		 *
+		 * If the guest never acked the interrupt we have to sample
+		 * the physical line and set the line level, because the
+		 * device state could have changed or we simply need to
+		 * process the still pending interrupt later.
+		 *
+		 * If this causes us to lower the level, we have to also clear
+		 * the physical active state, since we will otherwise never be
+		 * told when the interrupt becomes asserted again.
+		 */
+		if (vgic_irq_is_mapped_level(irq) && (val & ICH_LR_PENDING_BIT)) {
+			irq->line_level = vgic_get_phys_line_level(irq);
+
+			if (!irq->line_level)
+				vgic_irq_set_phys_active(irq, false);
+		}
+
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
@@ -145,6 +165,15 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
 			val |= ICH_LR_EOI;
 	}
 
+	/*
+	 * Level-triggered mapped IRQs are special because we only observe
+	 * rising edges as input to the VGIC.  We therefore lower the line
+	 * level here, so that we can take new virtual IRQs.  See
+	 * vgic_v3_fold_lr_state for more info.
+	 */
+	if (vgic_irq_is_mapped_level(irq) && (val & ICH_LR_PENDING_BIT))
+		irq->line_level = false;
+
 	/*
 	 * We currently only support Group1 interrupts, which is a
 	 * known defect. This needs to be addressed at some point.
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 786cce7bd2ec..423a572c92f5 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -144,6 +144,29 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 	kfree(irq);
 }
 
+/* Get the input level of a mapped IRQ directly from the physical GIC */
+bool vgic_get_phys_line_level(struct vgic_irq *irq)
+{
+	bool line_level;
+
+	BUG_ON(!irq->hw);
+
+	WARN_ON(irq_get_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_PENDING,
+				      &line_level));
+	return line_level;
+}
+
+/* Set/Clear the physical active state */
+void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active)
+{
+
+	BUG_ON(!irq->hw);
+	WARN_ON(irq_set_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_ACTIVE,
+				      active));
+}
+
 /**
  * kvm_vgic_target_oracle - compute the target vcpu for an irq
  *
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index efbcf8f96f9c..d0787983a357 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -104,6 +104,11 @@ static inline bool irq_is_pending(struct vgic_irq *irq)
 		return irq->pending_latch || irq->line_level;
 }
 
+static inline bool vgic_irq_is_mapped_level(struct vgic_irq *irq)
+{
+	return irq->config == VGIC_CONFIG_LEVEL && irq->hw;
+}
+
 /*
  * This struct provides an intermediate representation of the fields contained
  * in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC
@@ -140,6 +145,8 @@ vgic_get_mmio_region(struct kvm_vcpu *vcpu, struct vgic_io_device *iodev,
 struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			      u32 intid);
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
+bool vgic_get_phys_line_level(struct vgic_irq *irq);
+void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
 bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 			   unsigned long flags);
 void vgic_kick_vcpus(struct kvm *kvm);
-- 
2.14.2

[PATCH v5 4/8] KVM: arm/arm64: vgic: Support level-triggered mapped interrupts

[Christoffer Dall]

Level-triggered mapped IRQs are special because we only observe rising
edges as input to the VGIC, and we don't set the EOI flag and therefore
are not told when the level goes down, so that we can re-queue a new
interrupt when the level goes up.

One way to solve this problem is to side-step the logic of the VGIC and
special case the validation in the injection path, but it has the
unfortunate drawback of having to peak into the physical GIC state
whenever we want to know if the interrupt is pending on the virtual
distributor.

Instead, we can maintain the current semantics of a level triggered
interrupt by sort of treating it as an edge-triggered interrupt,
following from the fact that we only observe an asserting edge.  This
requires us to be a bit careful when populating the LRs and when folding
the state back in though:

 * We lower the line level when populating the LR, so that when
   subsequently observing an asserting edge, the VGIC will do the right
   thing.

 * If the guest never acked the interrupt while running (for example if
   it had masked interrupts at the CPU level while running), we have
   to preserve the pending state of the LR and move it back to the
   line_level field of the struct irq when folding LR state.

   If the guest never acked the interrupt while running, but changed the
   device state and lowered the line (again with interrupts masked) then
   we need to observe this change in the line_level.

   Both of the above situations are solved by sampling the physical line
   and set the line level when folding the LR back.

 * Finally, if the guest never acked the interrupt while running and
   sampling the line reveals that the device state has changed and the
   line has been lowered, we must clear the physical active state, since
   we will otherwise never be told when the interrupt becomes asserted
   again.

This has the added benefit of making the timer optimization patches
(https://lists.cs.columbia.edu/pipermail/kvmarm/2017-July/026343.html) a
bit simpler, because the timer code doesn't have to clear the active
state on the sync anymore.  It also potentially improves the performance
of the timer implementation because the GIC knows the state or the LR
and only needs to clear the
active state when the pending bit in the LR is still set, where the
timer has to always clear it when returning from running the guest with
an injected timer interrupt.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-v2.c | 29 +++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic-v3.c | 29 +++++++++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic.c    | 23 +++++++++++++++++++++++
 virt/kvm/arm/vgic/vgic.h    |  7 +++++++
 4 files changed, 88 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index 80897102da26..c32d7b93ffd1 100644
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -105,6 +105,26 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu)
 				irq->pending_latch = false;
 		}
 
+		/*
+		 * Level-triggered mapped IRQs are special because we only
+		 * observe rising edges as input to the VGIC.
+		 *
+		 * If the guest never acked the interrupt we have to sample
+		 * the physical line and set the line level, because the
+		 * device state could have changed or we simply need to
+		 * process the still pending interrupt later.
+		 *
+		 * If this causes us to lower the level, we have to also clear
+		 * the physical active state, since we will otherwise never be
+		 * told when the interrupt becomes asserted again.
+		 */
+		if (vgic_irq_is_mapped_level(irq) && (val & GICH_LR_PENDING_BIT)) {
+			irq->line_level = vgic_get_phys_line_level(irq);
+
+			if (!irq->line_level)
+				vgic_irq_set_phys_active(irq, false);
+		}
+
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
@@ -162,6 +182,15 @@ void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
 			val |= GICH_LR_EOI;
 	}
 
+	/*
+	 * Level-triggered mapped IRQs are special because we only observe
+	 * rising edges as input to the VGIC.  We therefore lower the line
+	 * level here, so that we can take new virtual IRQs.  See
+	 * vgic_v2_fold_lr_state for more info.
+	 */
+	if (vgic_irq_is_mapped_level(irq) && (val & GICH_LR_PENDING_BIT))
+		irq->line_level = false;
+
 	/* The GICv2 LR only holds five bits of priority. */
 	val |= (irq->priority >> 3) << GICH_LR_PRIORITY_SHIFT;
 
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index f47e8481fa45..6b329414e57a 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -96,6 +96,26 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
 				irq->pending_latch = false;
 		}
 
+		/*
+		 * Level-triggered mapped IRQs are special because we only
+		 * observe rising edges as input to the VGIC.
+		 *
+		 * If the guest never acked the interrupt we have to sample
+		 * the physical line and set the line level, because the
+		 * device state could have changed or we simply need to
+		 * process the still pending interrupt later.
+		 *
+		 * If this causes us to lower the level, we have to also clear
+		 * the physical active state, since we will otherwise never be
+		 * told when the interrupt becomes asserted again.
+		 */
+		if (vgic_irq_is_mapped_level(irq) && (val & ICH_LR_PENDING_BIT)) {
+			irq->line_level = vgic_get_phys_line_level(irq);
+
+			if (!irq->line_level)
+				vgic_irq_set_phys_active(irq, false);
+		}
+
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
@@ -145,6 +165,15 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr)
 			val |= ICH_LR_EOI;
 	}
 
+	/*
+	 * Level-triggered mapped IRQs are special because we only observe
+	 * rising edges as input to the VGIC.  We therefore lower the line
+	 * level here, so that we can take new virtual IRQs.  See
+	 * vgic_v3_fold_lr_state for more info.
+	 */
+	if (vgic_irq_is_mapped_level(irq) && (val & ICH_LR_PENDING_BIT))
+		irq->line_level = false;
+
 	/*
 	 * We currently only support Group1 interrupts, which is a
 	 * known defect. This needs to be addressed at some point.
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 786cce7bd2ec..423a572c92f5 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -144,6 +144,29 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 	kfree(irq);
 }
 
+/* Get the input level of a mapped IRQ directly from the physical GIC */
+bool vgic_get_phys_line_level(struct vgic_irq *irq)
+{
+	bool line_level;
+
+	BUG_ON(!irq->hw);
+
+	WARN_ON(irq_get_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_PENDING,
+				      &line_level));
+	return line_level;
+}
+
+/* Set/Clear the physical active state */
+void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active)
+{
+
+	BUG_ON(!irq->hw);
+	WARN_ON(irq_set_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_ACTIVE,
+				      active));
+}
+
 /**
  * kvm_vgic_target_oracle - compute the target vcpu for an irq
  *
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index efbcf8f96f9c..d0787983a357 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -104,6 +104,11 @@ static inline bool irq_is_pending(struct vgic_irq *irq)
 		return irq->pending_latch || irq->line_level;
 }
 
+static inline bool vgic_irq_is_mapped_level(struct vgic_irq *irq)
+{
+	return irq->config == VGIC_CONFIG_LEVEL && irq->hw;
+}
+
 /*
  * This struct provides an intermediate representation of the fields contained
  * in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC
@@ -140,6 +145,8 @@ vgic_get_mmio_region(struct kvm_vcpu *vcpu, struct vgic_io_device *iodev,
 struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			      u32 intid);
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
+bool vgic_get_phys_line_level(struct vgic_irq *irq);
+void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
 bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 			   unsigned long flags);
 void vgic_kick_vcpus(struct kvm *kvm);
-- 
2.14.2

[PATCH v5 5/8] KVM: arm/arm64: Support a vgic interrupt line level sample function

[Christoffer Dall]

The GIC sometimes need to sample the physical line of a mapped
interrupt.  As we know this to be notoriously slow, provide a callback
function for devices (such as the timer) which can do this much faster
than talking to the distributor, for example by comparing a few
in-memory values.  Fall back to the good old method of poking the
physical GIC if no callback is provided.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 include/kvm/arm_vgic.h    | 13 ++++++++++++-
 virt/kvm/arm/arch_timer.c |  3 ++-
 virt/kvm/arm/vgic/vgic.c  | 12 +++++++++---
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 8c896540a72c..cdbd142ca7f2 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -130,6 +130,17 @@ struct vgic_irq {
 	u8 priority;
 	enum vgic_irq_config config;	/* Level or edge */
 
+	/*
+	 * Callback function pointer to in-kernel devices that can tell us the
+	 * state of the input level of mapped level-triggered IRQ faster than
+	 * peaking into the physical GIC.
+	 *
+	 * Always called in non-preemptible section and the functions can use
+	 * kvm_arm_get_running_vcpu() to get the vcpu pointer for private
+	 * IRQs.
+	 */
+	bool (*get_input_level)(int vintid);
+
 	void *owner;			/* Opaque pointer to reserve an interrupt
 					   for in-kernel devices. */
 };
@@ -331,7 +342,7 @@ void kvm_vgic_init_cpu_hardware(void);
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 			bool level, void *owner);
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid);
+			  u32 vintid, bool (*get_input_level)(int vindid));
 int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid);
 bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int vintid);
 
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 5f8ad8e3f3ff..8f804ba5896f 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -834,7 +834,8 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 	}
 
-	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq);
+	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
+				    NULL);
 	if (ret)
 		return ret;
 
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 423a572c92f5..91266960dbd4 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -151,6 +151,9 @@ bool vgic_get_phys_line_level(struct vgic_irq *irq)
 
 	BUG_ON(!irq->hw);
 
+	if (irq->get_input_level)
+		return irq->get_input_level(irq->intid);
+
 	WARN_ON(irq_get_irqchip_state(irq->host_irq,
 				      IRQCHIP_STATE_PENDING,
 				      &line_level));
@@ -436,7 +439,8 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 
 /* @irq->irq_lock must be held */
 static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
-			    unsigned int host_irq)
+			    unsigned int host_irq,
+			    bool (*get_input_level)(int vindid))
 {
 	struct irq_desc *desc;
 	struct irq_data *data;
@@ -456,6 +460,7 @@ static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	irq->hw = true;
 	irq->host_irq = host_irq;
 	irq->hwintid = data->hwirq;
+	irq->get_input_level = get_input_level;
 	return 0;
 }
 
@@ -464,10 +469,11 @@ static inline void kvm_vgic_unmap_irq(struct vgic_irq *irq)
 {
 	irq->hw = false;
 	irq->hwintid = 0;
+	irq->get_input_level = NULL;
 }
 
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid)
+			  u32 vintid, bool (*get_input_level)(int vindid))
 {
 	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
 	unsigned long flags;
@@ -476,7 +482,7 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
 	BUG_ON(!irq);
 
 	spin_lock_irqsave(&irq->irq_lock, flags);
-	ret = kvm_vgic_map_irq(vcpu, irq, host_irq);
+	ret = kvm_vgic_map_irq(vcpu, irq, host_irq, get_input_level);
 	spin_unlock_irqrestore(&irq->irq_lock, flags);
 	vgic_put_irq(vcpu->kvm, irq);
 
-- 
2.14.2

[PATCH v5 5/8] KVM: arm/arm64: Support a vgic interrupt line level sample function

[Christoffer Dall]

The GIC sometimes need to sample the physical line of a mapped
interrupt.  As we know this to be notoriously slow, provide a callback
function for devices (such as the timer) which can do this much faster
than talking to the distributor, for example by comparing a few
in-memory values.  Fall back to the good old method of poking the
physical GIC if no callback is provided.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 include/kvm/arm_vgic.h    | 13 ++++++++++++-
 virt/kvm/arm/arch_timer.c |  3 ++-
 virt/kvm/arm/vgic/vgic.c  | 12 +++++++++---
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 8c896540a72c..cdbd142ca7f2 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -130,6 +130,17 @@ struct vgic_irq {
 	u8 priority;
 	enum vgic_irq_config config;	/* Level or edge */
 
+	/*
+	 * Callback function pointer to in-kernel devices that can tell us the
+	 * state of the input level of mapped level-triggered IRQ faster than
+	 * peaking into the physical GIC.
+	 *
+	 * Always called in non-preemptible section and the functions can use
+	 * kvm_arm_get_running_vcpu() to get the vcpu pointer for private
+	 * IRQs.
+	 */
+	bool (*get_input_level)(int vintid);
+
 	void *owner;			/* Opaque pointer to reserve an interrupt
 					   for in-kernel devices. */
 };
@@ -331,7 +342,7 @@ void kvm_vgic_init_cpu_hardware(void);
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 			bool level, void *owner);
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid);
+			  u32 vintid, bool (*get_input_level)(int vindid));
 int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid);
 bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int vintid);
 
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 5f8ad8e3f3ff..8f804ba5896f 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -834,7 +834,8 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 	}
 
-	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq);
+	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
+				    NULL);
 	if (ret)
 		return ret;
 
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 423a572c92f5..91266960dbd4 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -151,6 +151,9 @@ bool vgic_get_phys_line_level(struct vgic_irq *irq)
 
 	BUG_ON(!irq->hw);
 
+	if (irq->get_input_level)
+		return irq->get_input_level(irq->intid);
+
 	WARN_ON(irq_get_irqchip_state(irq->host_irq,
 				      IRQCHIP_STATE_PENDING,
 				      &line_level));
@@ -436,7 +439,8 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 
 /* @irq->irq_lock must be held */
 static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
-			    unsigned int host_irq)
+			    unsigned int host_irq,
+			    bool (*get_input_level)(int vindid))
 {
 	struct irq_desc *desc;
 	struct irq_data *data;
@@ -456,6 +460,7 @@ static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	irq->hw = true;
 	irq->host_irq = host_irq;
 	irq->hwintid = data->hwirq;
+	irq->get_input_level = get_input_level;
 	return 0;
 }
 
@@ -464,10 +469,11 @@ static inline void kvm_vgic_unmap_irq(struct vgic_irq *irq)
 {
 	irq->hw = false;
 	irq->hwintid = 0;
+	irq->get_input_level = NULL;
 }
 
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
-			  u32 vintid)
+			  u32 vintid, bool (*get_input_level)(int vindid))
 {
 	struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
 	unsigned long flags;
@@ -476,7 +482,7 @@ int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
 	BUG_ON(!irq);
 
 	spin_lock_irqsave(&irq->irq_lock, flags);
-	ret = kvm_vgic_map_irq(vcpu, irq, host_irq);
+	ret = kvm_vgic_map_irq(vcpu, irq, host_irq, get_input_level);
 	spin_unlock_irqrestore(&irq->irq_lock, flags);
 	vgic_put_irq(vcpu->kvm, irq);
 
-- 
2.14.2

[PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Christoffer Dall]

For mapped IRQs (with the HW bit set in the LR) we have to follow some
rules of the architecture.  One of these rules is that VM must not be
allowed to deactivate a virtual interrupt with the HW bit set unless the
physical interrupt is also active.

This works fine when injecting mapped interrupts, because we leave it up
to the injector to either set EOImode==1 or manually set the active
state of the physical interrupt.

However, the guest can set virtual interrupt to be pending or active by
writing to the virtual distributor, which could lead to deactivating a
virtual interrupt with the HW bit set without the physical interrupt
being active.

We could set the physical interrupt to active whenever we are about to
enter the VM with a HW interrupt either pending or active, but that
would be really slow, especially on GICv2.  So we take the long way
around and do the hard work when needed, which is expected to be
extremely rare.

When the VM sets the pending state for a HW interrupt on the virtual
distributor we set the active state on the physical distributor, because
the virtual interrupt can become active and then the guest can
deactivate it.

When the VM clears the pending state we also clear it on the physical
side, because the injector might otherwise raise the interrupt.  We also
clear the physical active state when the virtual interrupt is not
active, since otherwise a SPEND/CPEND sequence from the guest would
prevent signaling of future interrupts.

Changing the state of mapped interrupts from userspace is not supported,
and it's expected that userspace unmaps devices from VFIO before
attempting to set the interrupt state, because the interrupt state is
driven by hardware.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
 virt/kvm/arm/vgic/vgic.c      |  7 +++++
 virt/kvm/arm/vgic/vgic.h      |  1 +
 3 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 6113cf850f47..294e949ece24 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -16,6 +16,7 @@
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 #include <kvm/iodev.h>
+#include <kvm/arm_arch_timer.h>
 #include <kvm/arm_vgic.h>
 
 #include "vgic.h"
@@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
 	return vcpu;
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				 bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->pending_latch = true;
+
+	if (!is_uaccess)
+		vgic_irq_set_phys_active(irq, true);
+}
+
 void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
 {
+	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -154,17 +167,45 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
 
 		spin_lock_irqsave(&irq->irq_lock, flags);
-		irq->pending_latch = true;
-
+		if (irq->hw)
+			vgic_hw_irq_spending(vcpu, irq, is_uaccess);
+		else
+			irq->pending_latch = true;
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_cpending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				 bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->pending_latch = false;
+
+	if (!is_uaccess) {
+		/*
+		 * We don't want the guest to effectively mask the physical
+		 * interrupt by doing a write to SPENDR followed by a write to
+		 * CPENDR for HW interrupts, so we clear the active state on
+		 * the physical side if the virtual interrupt is not active.
+		 * This may lead to taking an additional interrupt on the
+		 * host, but that should not be a problem as the worst that
+		 * can happen is an additional vgic injection.  We also clear
+		 * the pending state to maintain proper semantics for edge HW
+		 * interrupts.
+		 */
+		vgic_irq_set_phys_pending(irq, false);
+		if (!irq->active)
+			vgic_irq_set_phys_active(irq, false);
+	}
+}
+
 void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
 {
+	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -174,7 +215,10 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 
 		spin_lock_irqsave(&irq->irq_lock, flags);
 
-		irq->pending_latch = false;
+		if (irq->hw)
+			vgic_hw_irq_cpending(vcpu, irq, is_uaccess);
+		else
+			irq->pending_latch = false;
 
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
@@ -201,8 +245,19 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
 	return value;
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				      bool active, bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->active = active;;
+
+	if (!is_uaccess)
+		vgic_irq_set_phys_active(irq, active);
+}
+
 static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
-				    bool new_active_state)
+				    bool active)
 {
 	unsigned long flags;
 	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
@@ -230,8 +285,12 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	       irq->vcpu->cpu != -1) /* VCPU thread is running */
 		cond_resched_lock(&irq->irq_lock);
 
-	irq->active = new_active_state;
-	if (new_active_state)
+	if (irq->hw)
+		vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu);
+	else
+		irq->active = active;
+
+	if (irq->active)
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 	else
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 91266960dbd4..2d40384481d0 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -144,6 +144,13 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 	kfree(irq);
 }
 
+void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending)
+{
+	WARN_ON(irq_set_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_PENDING,
+				      pending));
+}
+
 /* Get the input level of a mapped IRQ directly from the physical GIC */
 bool vgic_get_phys_line_level(struct vgic_irq *irq)
 {
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index d0787983a357..12c37b89f7a3 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -146,6 +146,7 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			      u32 intid);
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
 bool vgic_get_phys_line_level(struct vgic_irq *irq);
+void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending);
 void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
 bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 			   unsigned long flags);
-- 
2.14.2

[PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Christoffer Dall]

For mapped IRQs (with the HW bit set in the LR) we have to follow some
rules of the architecture.  One of these rules is that VM must not be
allowed to deactivate a virtual interrupt with the HW bit set unless the
physical interrupt is also active.

This works fine when injecting mapped interrupts, because we leave it up
to the injector to either set EOImode==1 or manually set the active
state of the physical interrupt.

However, the guest can set virtual interrupt to be pending or active by
writing to the virtual distributor, which could lead to deactivating a
virtual interrupt with the HW bit set without the physical interrupt
being active.

We could set the physical interrupt to active whenever we are about to
enter the VM with a HW interrupt either pending or active, but that
would be really slow, especially on GICv2.  So we take the long way
around and do the hard work when needed, which is expected to be
extremely rare.

When the VM sets the pending state for a HW interrupt on the virtual
distributor we set the active state on the physical distributor, because
the virtual interrupt can become active and then the guest can
deactivate it.

When the VM clears the pending state we also clear it on the physical
side, because the injector might otherwise raise the interrupt.  We also
clear the physical active state when the virtual interrupt is not
active, since otherwise a SPEND/CPEND sequence from the guest would
prevent signaling of future interrupts.

Changing the state of mapped interrupts from userspace is not supported,
and it's expected that userspace unmaps devices from VFIO before
attempting to set the interrupt state, because the interrupt state is
driven by hardware.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
 virt/kvm/arm/vgic/vgic.c      |  7 +++++
 virt/kvm/arm/vgic/vgic.h      |  1 +
 3 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 6113cf850f47..294e949ece24 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -16,6 +16,7 @@
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 #include <kvm/iodev.h>
+#include <kvm/arm_arch_timer.h>
 #include <kvm/arm_vgic.h>
 
 #include "vgic.h"
@@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
 	return vcpu;
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				 bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->pending_latch = true;
+
+	if (!is_uaccess)
+		vgic_irq_set_phys_active(irq, true);
+}
+
 void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
 {
+	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -154,17 +167,45 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
 		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
 
 		spin_lock_irqsave(&irq->irq_lock, flags);
-		irq->pending_latch = true;
-
+		if (irq->hw)
+			vgic_hw_irq_spending(vcpu, irq, is_uaccess);
+		else
+			irq->pending_latch = true;
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_cpending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				 bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->pending_latch = false;
+
+	if (!is_uaccess) {
+		/*
+		 * We don't want the guest to effectively mask the physical
+		 * interrupt by doing a write to SPENDR followed by a write to
+		 * CPENDR for HW interrupts, so we clear the active state on
+		 * the physical side if the virtual interrupt is not active.
+		 * This may lead to taking an additional interrupt on the
+		 * host, but that should not be a problem as the worst that
+		 * can happen is an additional vgic injection.  We also clear
+		 * the pending state to maintain proper semantics for edge HW
+		 * interrupts.
+		 */
+		vgic_irq_set_phys_pending(irq, false);
+		if (!irq->active)
+			vgic_irq_set_phys_active(irq, false);
+	}
+}
+
 void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 			      gpa_t addr, unsigned int len,
 			      unsigned long val)
 {
+	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -174,7 +215,10 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
 
 		spin_lock_irqsave(&irq->irq_lock, flags);
 
-		irq->pending_latch = false;
+		if (irq->hw)
+			vgic_hw_irq_cpending(vcpu, irq, is_uaccess);
+		else
+			irq->pending_latch = false;
 
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
 		vgic_put_irq(vcpu->kvm, irq);
@@ -201,8 +245,19 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
 	return value;
 }
 
+/* Must be called with irq->irq_lock held */
+static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
+				      bool active, bool is_uaccess)
+{
+	if (!is_uaccess)
+		irq->active = active;;
+
+	if (!is_uaccess)
+		vgic_irq_set_phys_active(irq, active);
+}
+
 static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
-				    bool new_active_state)
+				    bool active)
 {
 	unsigned long flags;
 	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
@@ -230,8 +285,12 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 	       irq->vcpu->cpu != -1) /* VCPU thread is running */
 		cond_resched_lock(&irq->irq_lock);
 
-	irq->active = new_active_state;
-	if (new_active_state)
+	if (irq->hw)
+		vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu);
+	else
+		irq->active = active;
+
+	if (irq->active)
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 	else
 		spin_unlock_irqrestore(&irq->irq_lock, flags);
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 91266960dbd4..2d40384481d0 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -144,6 +144,13 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
 	kfree(irq);
 }
 
+void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending)
+{
+	WARN_ON(irq_set_irqchip_state(irq->host_irq,
+				      IRQCHIP_STATE_PENDING,
+				      pending));
+}
+
 /* Get the input level of a mapped IRQ directly from the physical GIC */
 bool vgic_get_phys_line_level(struct vgic_irq *irq)
 {
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index d0787983a357..12c37b89f7a3 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -146,6 +146,7 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
 			      u32 intid);
 void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
 bool vgic_get_phys_line_level(struct vgic_irq *irq);
+void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending);
 void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
 bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 			   unsigned long flags);
-- 
2.14.2

[PATCH v5 7/8] KVM: arm/arm64: Provide a get_input_level for the arch timer

[Christoffer Dall]

The VGIC can now support the life-cycle of mapped level-triggered
interrupts, and we no longer have to read back the timer state on every
exit from the VM if we had an asserted timer interrupt signal, because
the VGIC already knows if we hit the unlikely case where the guest
disables the timer without ACKing the virtual timer interrupt.

This means we rework a bit of the code to factor out the functionality
to snapshot the timer state from vtimer_save_state(), and we can reuse
this functionality in the sync path when we have an irqchip in
userspace, and also to support our implementation of the
get_input_level() function for the timer.

This change also means that we can no longer rely on the timer's view of
the interrupt line to set the active state, because we no longer
maintain this state for mapped interrupts when exiting from the guest.
Instead, we only set the active state if the virtual interrupt is
active, and otherwise we simply let the timer fire again and raise the
virtual interrupt from the ISR.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 include/kvm/arm_arch_timer.h |  2 ++
 virt/kvm/arm/arch_timer.c    | 76 +++++++++++++++++++++-----------------------
 2 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 6e45608b2399..b1dcfde0a3ef 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
 
 void kvm_timer_init_vhe(void);
 
+bool kvm_arch_timer_get_input_level(int vintid);
+
 #define vcpu_vtimer(v)	(&(v)->arch.timer_cpu.vtimer)
 #define vcpu_ptimer(v)	(&(v)->arch.timer_cpu.ptimer)
 
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 8f804ba5896f..bcde6bb99669 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
 	phys_timer_emulate(vcpu);
 }
 
+static void __timer_snapshot_state(struct arch_timer_context *timer)
+{
+	timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+	timer->cnt_cval = read_sysreg_el0(cntv_cval);
+}
+
 static void vtimer_save_state(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
 	if (!vtimer->loaded)
 		goto out;
 
-	if (timer->enabled) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
-	}
+	if (timer->enabled)
+		__timer_snapshot_state(vtimer);
 
 	/* Disable the virtual timer */
 	write_sysreg_el0(0, cntv_ctl);
@@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
 	bool phys_active;
 	int ret;
 
-	phys_active = vtimer->irq.level ||
-		      kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
+	phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
 
 	ret = irq_set_irqchip_state(host_vtimer_irq,
 				    IRQCHIP_STATE_ACTIVE,
@@ -535,27 +538,19 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	set_cntvoff(0);
 }
 
-static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
+/*
+ * With a userspace irqchip we have to check if the guest de-asserted the
+ * timer and if so, unmask the timer irq signal on the host interrupt
+ * controller to ensure that we see future timer signals.
+ */
+static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 
 	if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
-		kvm_vtimer_update_mask_user(vcpu);
-		return;
-	}
-
-	/*
-	 * If the guest disabled the timer without acking the interrupt, then
-	 * we must make sure the physical and virtual active states are in
-	 * sync by deactivating the physical interrupt, because otherwise we
-	 * wouldn't see the next timer interrupt in the host.
-	 */
-	if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) {
-		int ret;
-		ret = irq_set_irqchip_state(host_vtimer_irq,
-					    IRQCHIP_STATE_ACTIVE,
-					    false);
-		WARN_ON(ret);
+		__timer_snapshot_state(vtimer);
+		if (!kvm_timer_should_fire(vtimer))
+			kvm_vtimer_update_mask_user(vcpu);
 	}
 }
 
@@ -568,21 +563,7 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
  */
 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 {
-	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
-
-	/*
-	 * If we entered the guest with the vtimer output asserted we have to
-	 * check if the guest has modified the timer so that we should lower
-	 * the line at this point.
-	 */
-	if (vtimer->irq.level) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
-		if (!kvm_timer_should_fire(vtimer)) {
-			kvm_timer_update_irq(vcpu, false, vtimer);
-			unmask_vtimer_irq(vcpu);
-		}
-	}
+	unmask_vtimer_irq_user(vcpu);
 }
 
 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -813,6 +794,23 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
 	return true;
 }
 
+bool kvm_arch_timer_get_input_level(int vintid)
+{
+	struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
+	struct arch_timer_context *timer;
+
+
+	if (vintid == vcpu_vtimer(vcpu)->irq.irq)
+		timer = vcpu_vtimer(vcpu);
+	else
+		BUG(); /* We only map the vtimer so far */
+
+	if (timer->loaded)
+		__timer_snapshot_state(timer);
+
+	return kvm_timer_should_fire(timer);
+}
+
 int kvm_timer_enable(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -835,7 +833,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 	}
 
 	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
-				    NULL);
+				    kvm_arch_timer_get_input_level);
 	if (ret)
 		return ret;
 
-- 
2.14.2

[PATCH v5 7/8] KVM: arm/arm64: Provide a get_input_level for the arch timer

[Christoffer Dall]

The VGIC can now support the life-cycle of mapped level-triggered
interrupts, and we no longer have to read back the timer state on every
exit from the VM if we had an asserted timer interrupt signal, because
the VGIC already knows if we hit the unlikely case where the guest
disables the timer without ACKing the virtual timer interrupt.

This means we rework a bit of the code to factor out the functionality
to snapshot the timer state from vtimer_save_state(), and we can reuse
this functionality in the sync path when we have an irqchip in
userspace, and also to support our implementation of the
get_input_level() function for the timer.

This change also means that we can no longer rely on the timer's view of
the interrupt line to set the active state, because we no longer
maintain this state for mapped interrupts when exiting from the guest.
Instead, we only set the active state if the virtual interrupt is
active, and otherwise we simply let the timer fire again and raise the
virtual interrupt from the ISR.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 include/kvm/arm_arch_timer.h |  2 ++
 virt/kvm/arm/arch_timer.c    | 76 +++++++++++++++++++++-----------------------
 2 files changed, 39 insertions(+), 39 deletions(-)

diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
index 6e45608b2399..b1dcfde0a3ef 100644
--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
 
 void kvm_timer_init_vhe(void);
 
+bool kvm_arch_timer_get_input_level(int vintid);
+
 #define vcpu_vtimer(v)	(&(v)->arch.timer_cpu.vtimer)
 #define vcpu_ptimer(v)	(&(v)->arch.timer_cpu.ptimer)
 
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 8f804ba5896f..bcde6bb99669 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
 	phys_timer_emulate(vcpu);
 }
 
+static void __timer_snapshot_state(struct arch_timer_context *timer)
+{
+	timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+	timer->cnt_cval = read_sysreg_el0(cntv_cval);
+}
+
 static void vtimer_save_state(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
 	if (!vtimer->loaded)
 		goto out;
 
-	if (timer->enabled) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
-	}
+	if (timer->enabled)
+		__timer_snapshot_state(vtimer);
 
 	/* Disable the virtual timer */
 	write_sysreg_el0(0, cntv_ctl);
@@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
 	bool phys_active;
 	int ret;
 
-	phys_active = vtimer->irq.level ||
-		      kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
+	phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
 
 	ret = irq_set_irqchip_state(host_vtimer_irq,
 				    IRQCHIP_STATE_ACTIVE,
@@ -535,27 +538,19 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	set_cntvoff(0);
 }
 
-static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
+/*
+ * With a userspace irqchip we have to check if the guest de-asserted the
+ * timer and if so, unmask the timer irq signal on the host interrupt
+ * controller to ensure that we see future timer signals.
+ */
+static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 
 	if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
-		kvm_vtimer_update_mask_user(vcpu);
-		return;
-	}
-
-	/*
-	 * If the guest disabled the timer without acking the interrupt, then
-	 * we must make sure the physical and virtual active states are in
-	 * sync by deactivating the physical interrupt, because otherwise we
-	 * wouldn't see the next timer interrupt in the host.
-	 */
-	if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) {
-		int ret;
-		ret = irq_set_irqchip_state(host_vtimer_irq,
-					    IRQCHIP_STATE_ACTIVE,
-					    false);
-		WARN_ON(ret);
+		__timer_snapshot_state(vtimer);
+		if (!kvm_timer_should_fire(vtimer))
+			kvm_vtimer_update_mask_user(vcpu);
 	}
 }
 
@@ -568,21 +563,7 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
  */
 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 {
-	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
-
-	/*
-	 * If we entered the guest with the vtimer output asserted we have to
-	 * check if the guest has modified the timer so that we should lower
-	 * the line at this point.
-	 */
-	if (vtimer->irq.level) {
-		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
-		if (!kvm_timer_should_fire(vtimer)) {
-			kvm_timer_update_irq(vcpu, false, vtimer);
-			unmask_vtimer_irq(vcpu);
-		}
-	}
+	unmask_vtimer_irq_user(vcpu);
 }
 
 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -813,6 +794,23 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
 	return true;
 }
 
+bool kvm_arch_timer_get_input_level(int vintid)
+{
+	struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
+	struct arch_timer_context *timer;
+
+
+	if (vintid == vcpu_vtimer(vcpu)->irq.irq)
+		timer = vcpu_vtimer(vcpu);
+	else
+		BUG(); /* We only map the vtimer so far */
+
+	if (timer->loaded)
+		__timer_snapshot_state(timer);
+
+	return kvm_timer_should_fire(timer);
+}
+
 int kvm_timer_enable(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -835,7 +833,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 	}
 
 	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
-				    NULL);
+				    kvm_arch_timer_get_input_level);
 	if (ret)
 		return ret;
 
-- 
2.14.2

[PATCH v5 8/8] KVM: arm/arm64: Avoid work when userspace iqchips are not used

[Christoffer Dall]

We currently check if the VM has a userspace irqchip on every exit from
the VCPU, and if so, we do some work to ensure correct timer behavior.
This is unfortunate, as we could avoid doing any work entirely, if we
didn't have to support irqchip in userspace.

Realizing the userspace irqchip on ARM is mostly a developer or hobby
feature, and is unlikely to be used in servers or other scenarios where
performance is a priority, we can use a refcounted static key to only
check the irqchip configuration when we have at least one VM that uses
an irqchip in userspace.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arch_timer.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index bcde6bb99669..7b27316d4c3f 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -51,6 +51,8 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
 				 struct arch_timer_context *timer_ctx);
 static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
 
+static DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
+
 u64 kvm_phys_timer_read(void)
 {
 	return timecounter->cc->read(timecounter->cc);
@@ -563,7 +565,8 @@ static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
  */
 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 {
-	unmask_vtimer_irq_user(vcpu);
+	if (static_branch_unlikely(&userspace_irqchip_in_use))
+		unmask_vtimer_irq_user(vcpu);
 }
 
 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -768,6 +771,8 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
 	soft_timer_cancel(&timer->bg_timer, &timer->expired);
 	soft_timer_cancel(&timer->phys_timer, NULL);
 	kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
+	if (timer->enabled && !irqchip_in_kernel(vcpu->kvm))
+		static_branch_dec(&userspace_irqchip_in_use);
 }
 
 static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
@@ -821,8 +826,10 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 		return 0;
 
 	/* Without a VGIC we do not map virtual IRQs to physical IRQs */
-	if (!irqchip_in_kernel(vcpu->kvm))
+	if (!irqchip_in_kernel(vcpu->kvm)) {
+		static_branch_inc(&userspace_irqchip_in_use);
 		goto no_vgic;
+	}
 
 	if (!vgic_initialized(vcpu->kvm))
 		return -ENODEV;
-- 
2.14.2

[PATCH v5 8/8] KVM: arm/arm64: Avoid work when userspace iqchips are not used

[Christoffer Dall]

We currently check if the VM has a userspace irqchip on every exit from
the VCPU, and if so, we do some work to ensure correct timer behavior.
This is unfortunate, as we could avoid doing any work entirely, if we
didn't have to support irqchip in userspace.

Realizing the userspace irqchip on ARM is mostly a developer or hobby
feature, and is unlikely to be used in servers or other scenarios where
performance is a priority, we can use a refcounted static key to only
check the irqchip configuration when we have at least one VM that uses
an irqchip in userspace.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arch_timer.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index bcde6bb99669..7b27316d4c3f 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -51,6 +51,8 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
 				 struct arch_timer_context *timer_ctx);
 static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
 
+static DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
+
 u64 kvm_phys_timer_read(void)
 {
 	return timecounter->cc->read(timecounter->cc);
@@ -563,7 +565,8 @@ static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
  */
 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 {
-	unmask_vtimer_irq_user(vcpu);
+	if (static_branch_unlikely(&userspace_irqchip_in_use))
+		unmask_vtimer_irq_user(vcpu);
 }
 
 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -768,6 +771,8 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
 	soft_timer_cancel(&timer->bg_timer, &timer->expired);
 	soft_timer_cancel(&timer->phys_timer, NULL);
 	kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
+	if (timer->enabled && !irqchip_in_kernel(vcpu->kvm))
+		static_branch_dec(&userspace_irqchip_in_use);
 }
 
 static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
@@ -821,8 +826,10 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
 		return 0;
 
 	/* Without a VGIC we do not map virtual IRQs to physical IRQs */
-	if (!irqchip_in_kernel(vcpu->kvm))
+	if (!irqchip_in_kernel(vcpu->kvm)) {
+		static_branch_inc(&userspace_irqchip_in_use);
 		goto no_vgic;
+	}
 
 	if (!vgic_initialized(vcpu->kvm))
 		return -ENODEV;
-- 
2.14.2

Re: [PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Andrew Jones]

On Mon, Nov 20, 2017 at 08:16:47PM +0100, Christoffer Dall wrote:
> For mapped IRQs (with the HW bit set in the LR) we have to follow some
> rules of the architecture.  One of these rules is that VM must not be
> allowed to deactivate a virtual interrupt with the HW bit set unless the
> physical interrupt is also active.
> 
> This works fine when injecting mapped interrupts, because we leave it up
> to the injector to either set EOImode==1 or manually set the active
> state of the physical interrupt.
> 
> However, the guest can set virtual interrupt to be pending or active by
> writing to the virtual distributor, which could lead to deactivating a
> virtual interrupt with the HW bit set without the physical interrupt
> being active.
> 
> We could set the physical interrupt to active whenever we are about to
> enter the VM with a HW interrupt either pending or active, but that
> would be really slow, especially on GICv2.  So we take the long way
> around and do the hard work when needed, which is expected to be
> extremely rare.
> 
> When the VM sets the pending state for a HW interrupt on the virtual
> distributor we set the active state on the physical distributor, because
> the virtual interrupt can become active and then the guest can
> deactivate it.
> 
> When the VM clears the pending state we also clear it on the physical
> side, because the injector might otherwise raise the interrupt.  We also
> clear the physical active state when the virtual interrupt is not
> active, since otherwise a SPEND/CPEND sequence from the guest would
> prevent signaling of future interrupts.
> 
> Changing the state of mapped interrupts from userspace is not supported,
> and it's expected that userspace unmaps devices from VFIO before
> attempting to set the interrupt state, because the interrupt state is
> driven by hardware.
> 
> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
>  virt/kvm/arm/vgic/vgic.c      |  7 +++++
>  virt/kvm/arm/vgic/vgic.h      |  1 +
>  3 files changed, 73 insertions(+), 6 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index 6113cf850f47..294e949ece24 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -16,6 +16,7 @@
>  #include <linux/kvm.h>
>  #include <linux/kvm_host.h>
>  #include <kvm/iodev.h>
> +#include <kvm/arm_arch_timer.h>
>  #include <kvm/arm_vgic.h>
>  
>  #include "vgic.h"
> @@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
>  	return vcpu;
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				 bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->pending_latch = true;
> +
> +	if (!is_uaccess)
> +		vgic_irq_set_phys_active(irq, true);

I see this whole patch has this two 'if (!is_uaccess)' checks pattern.
Is that meant to convey something? Or is the first condition not supposed
to have the '!'? (I'm lost with regards to the state tracking differences
between the guest and userspace and just reviewing superficially...)

> +}
> +
>  void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
>  {
> +	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
>  	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>  	int i;
>  	unsigned long flags;
> @@ -154,17 +167,45 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		spin_lock_irqsave(&irq->irq_lock, flags);
> -		irq->pending_latch = true;
> -
> +		if (irq->hw)
> +			vgic_hw_irq_spending(vcpu, irq, is_uaccess);
> +		else
> +			irq->pending_latch = true;
>  		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
>  		vgic_put_irq(vcpu->kvm, irq);
>  	}
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_cpending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				 bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->pending_latch = false;
> +
> +	if (!is_uaccess) {
> +		/*
> +		 * We don't want the guest to effectively mask the physical
> +		 * interrupt by doing a write to SPENDR followed by a write to
> +		 * CPENDR for HW interrupts, so we clear the active state on
> +		 * the physical side if the virtual interrupt is not active.
> +		 * This may lead to taking an additional interrupt on the
> +		 * host, but that should not be a problem as the worst that
> +		 * can happen is an additional vgic injection.  We also clear
> +		 * the pending state to maintain proper semantics for edge HW
> +		 * interrupts.
> +		 */
> +		vgic_irq_set_phys_pending(irq, false);
> +		if (!irq->active)
> +			vgic_irq_set_phys_active(irq, false);
> +	}
> +}
> +
>  void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
>  {
> +	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
>  	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>  	int i;
>  	unsigned long flags;
> @@ -174,7 +215,10 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  
>  		spin_lock_irqsave(&irq->irq_lock, flags);
>  
> -		irq->pending_latch = false;
> +		if (irq->hw)
> +			vgic_hw_irq_cpending(vcpu, irq, is_uaccess);
> +		else
> +			irq->pending_latch = false;
>  
>  		spin_unlock_irqrestore(&irq->irq_lock, flags);
>  		vgic_put_irq(vcpu->kvm, irq);
> @@ -201,8 +245,19 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
>  	return value;
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				      bool active, bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->active = active;;
> +
> +	if (!is_uaccess)
> +		vgic_irq_set_phys_active(irq, active);
> +}
> +
>  static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> -				    bool new_active_state)
> +				    bool active)
>  {
>  	unsigned long flags;
>  	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
> @@ -230,8 +285,12 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  	       irq->vcpu->cpu != -1) /* VCPU thread is running */
>  		cond_resched_lock(&irq->irq_lock);
>  
> -	irq->active = new_active_state;
> -	if (new_active_state)
> +	if (irq->hw)
> +		vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu);
> +	else
> +		irq->active = active;
> +
> +	if (irq->active)
>  		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
>  	else
>  		spin_unlock_irqrestore(&irq->irq_lock, flags);
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index 91266960dbd4..2d40384481d0 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -144,6 +144,13 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
>  	kfree(irq);
>  }
>  
> +void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending)
> +{
> +	WARN_ON(irq_set_irqchip_state(irq->host_irq,
> +				      IRQCHIP_STATE_PENDING,
> +				      pending));
> +}
> +
>  /* Get the input level of a mapped IRQ directly from the physical GIC */
>  bool vgic_get_phys_line_level(struct vgic_irq *irq)
>  {
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index d0787983a357..12c37b89f7a3 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -146,6 +146,7 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>  			      u32 intid);
>  void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
>  bool vgic_get_phys_line_level(struct vgic_irq *irq);
> +void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending);
>  void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
>  bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
>  			   unsigned long flags);
> -- 
> 2.14.2
> 

[PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Andrew Jones]

On Mon, Nov 20, 2017 at 08:16:47PM +0100, Christoffer Dall wrote:
> For mapped IRQs (with the HW bit set in the LR) we have to follow some
> rules of the architecture.  One of these rules is that VM must not be
> allowed to deactivate a virtual interrupt with the HW bit set unless the
> physical interrupt is also active.
> 
> This works fine when injecting mapped interrupts, because we leave it up
> to the injector to either set EOImode==1 or manually set the active
> state of the physical interrupt.
> 
> However, the guest can set virtual interrupt to be pending or active by
> writing to the virtual distributor, which could lead to deactivating a
> virtual interrupt with the HW bit set without the physical interrupt
> being active.
> 
> We could set the physical interrupt to active whenever we are about to
> enter the VM with a HW interrupt either pending or active, but that
> would be really slow, especially on GICv2.  So we take the long way
> around and do the hard work when needed, which is expected to be
> extremely rare.
> 
> When the VM sets the pending state for a HW interrupt on the virtual
> distributor we set the active state on the physical distributor, because
> the virtual interrupt can become active and then the guest can
> deactivate it.
> 
> When the VM clears the pending state we also clear it on the physical
> side, because the injector might otherwise raise the interrupt.  We also
> clear the physical active state when the virtual interrupt is not
> active, since otherwise a SPEND/CPEND sequence from the guest would
> prevent signaling of future interrupts.
> 
> Changing the state of mapped interrupts from userspace is not supported,
> and it's expected that userspace unmaps devices from VFIO before
> attempting to set the interrupt state, because the interrupt state is
> driven by hardware.
> 
> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
>  virt/kvm/arm/vgic/vgic.c      |  7 +++++
>  virt/kvm/arm/vgic/vgic.h      |  1 +
>  3 files changed, 73 insertions(+), 6 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index 6113cf850f47..294e949ece24 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -16,6 +16,7 @@
>  #include <linux/kvm.h>
>  #include <linux/kvm_host.h>
>  #include <kvm/iodev.h>
> +#include <kvm/arm_arch_timer.h>
>  #include <kvm/arm_vgic.h>
>  
>  #include "vgic.h"
> @@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
>  	return vcpu;
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				 bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->pending_latch = true;
> +
> +	if (!is_uaccess)
> +		vgic_irq_set_phys_active(irq, true);

I see this whole patch has this two 'if (!is_uaccess)' checks pattern.
Is that meant to convey something? Or is the first condition not supposed
to have the '!'? (I'm lost with regards to the state tracking differences
between the guest and userspace and just reviewing superficially...)

> +}
> +
>  void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
>  {
> +	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
>  	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>  	int i;
>  	unsigned long flags;
> @@ -154,17 +167,45 @@ void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>  
>  		spin_lock_irqsave(&irq->irq_lock, flags);
> -		irq->pending_latch = true;
> -
> +		if (irq->hw)
> +			vgic_hw_irq_spending(vcpu, irq, is_uaccess);
> +		else
> +			irq->pending_latch = true;
>  		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
>  		vgic_put_irq(vcpu->kvm, irq);
>  	}
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_cpending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				 bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->pending_latch = false;
> +
> +	if (!is_uaccess) {
> +		/*
> +		 * We don't want the guest to effectively mask the physical
> +		 * interrupt by doing a write to SPENDR followed by a write to
> +		 * CPENDR for HW interrupts, so we clear the active state on
> +		 * the physical side if the virtual interrupt is not active.
> +		 * This may lead to taking an additional interrupt on the
> +		 * host, but that should not be a problem as the worst that
> +		 * can happen is an additional vgic injection.  We also clear
> +		 * the pending state to maintain proper semantics for edge HW
> +		 * interrupts.
> +		 */
> +		vgic_irq_set_phys_pending(irq, false);
> +		if (!irq->active)
> +			vgic_irq_set_phys_active(irq, false);
> +	}
> +}
> +
>  void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
>  {
> +	bool is_uaccess = !vgic_get_mmio_requester_vcpu();
>  	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>  	int i;
>  	unsigned long flags;
> @@ -174,7 +215,10 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
>  
>  		spin_lock_irqsave(&irq->irq_lock, flags);
>  
> -		irq->pending_latch = false;
> +		if (irq->hw)
> +			vgic_hw_irq_cpending(vcpu, irq, is_uaccess);
> +		else
> +			irq->pending_latch = false;
>  
>  		spin_unlock_irqrestore(&irq->irq_lock, flags);
>  		vgic_put_irq(vcpu->kvm, irq);
> @@ -201,8 +245,19 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
>  	return value;
>  }
>  
> +/* Must be called with irq->irq_lock held */
> +static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> +				      bool active, bool is_uaccess)
> +{
> +	if (!is_uaccess)
> +		irq->active = active;;
> +
> +	if (!is_uaccess)
> +		vgic_irq_set_phys_active(irq, active);
> +}
> +
>  static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> -				    bool new_active_state)
> +				    bool active)
>  {
>  	unsigned long flags;
>  	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
> @@ -230,8 +285,12 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  	       irq->vcpu->cpu != -1) /* VCPU thread is running */
>  		cond_resched_lock(&irq->irq_lock);
>  
> -	irq->active = new_active_state;
> -	if (new_active_state)
> +	if (irq->hw)
> +		vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu);
> +	else
> +		irq->active = active;
> +
> +	if (irq->active)
>  		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
>  	else
>  		spin_unlock_irqrestore(&irq->irq_lock, flags);
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index 91266960dbd4..2d40384481d0 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -144,6 +144,13 @@ void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
>  	kfree(irq);
>  }
>  
> +void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending)
> +{
> +	WARN_ON(irq_set_irqchip_state(irq->host_irq,
> +				      IRQCHIP_STATE_PENDING,
> +				      pending));
> +}
> +
>  /* Get the input level of a mapped IRQ directly from the physical GIC */
>  bool vgic_get_phys_line_level(struct vgic_irq *irq)
>  {
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index d0787983a357..12c37b89f7a3 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -146,6 +146,7 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
>  			      u32 intid);
>  void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq);
>  bool vgic_get_phys_line_level(struct vgic_irq *irq);
> +void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending);
>  void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active);
>  bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
>  			   unsigned long flags);
> -- 
> 2.14.2
> 

Re: [PATCH v5 7/8] KVM: arm/arm64: Provide a get_input_level for the arch timer

[Andrew Jones]

On Mon, Nov 20, 2017 at 08:16:48PM +0100, Christoffer Dall wrote:
> The VGIC can now support the life-cycle of mapped level-triggered
> interrupts, and we no longer have to read back the timer state on every
> exit from the VM if we had an asserted timer interrupt signal, because
> the VGIC already knows if we hit the unlikely case where the guest
> disables the timer without ACKing the virtual timer interrupt.
> 
> This means we rework a bit of the code to factor out the functionality
> to snapshot the timer state from vtimer_save_state(), and we can reuse
> this functionality in the sync path when we have an irqchip in
> userspace, and also to support our implementation of the
> get_input_level() function for the timer.
> 
> This change also means that we can no longer rely on the timer's view of
> the interrupt line to set the active state, because we no longer
> maintain this state for mapped interrupts when exiting from the guest.
> Instead, we only set the active state if the virtual interrupt is
> active, and otherwise we simply let the timer fire again and raise the
> virtual interrupt from the ISR.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  include/kvm/arm_arch_timer.h |  2 ++
>  virt/kvm/arm/arch_timer.c    | 76 +++++++++++++++++++++-----------------------
>  2 files changed, 39 insertions(+), 39 deletions(-)
> 
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index 6e45608b2399..b1dcfde0a3ef 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
>  
>  void kvm_timer_init_vhe(void);
>  
> +bool kvm_arch_timer_get_input_level(int vintid);
> +
>  #define vcpu_vtimer(v)	(&(v)->arch.timer_cpu.vtimer)
>  #define vcpu_ptimer(v)	(&(v)->arch.timer_cpu.ptimer)
>  
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 8f804ba5896f..bcde6bb99669 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
>  	phys_timer_emulate(vcpu);
>  }
>  
> +static void __timer_snapshot_state(struct arch_timer_context *timer)
> +{
> +	timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> +	timer->cnt_cval = read_sysreg_el0(cntv_cval);
> +}
> +
>  static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  	if (!vtimer->loaded)
>  		goto out;
>  
> -	if (timer->enabled) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -	}
> +	if (timer->enabled)
> +		__timer_snapshot_state(vtimer);
>  
>  	/* Disable the virtual timer */
>  	write_sysreg_el0(0, cntv_ctl);
> @@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
>  	bool phys_active;
>  	int ret;
>  
> -	phys_active = vtimer->irq.level ||
> -		      kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
> +	phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
>  
>  	ret = irq_set_irqchip_state(host_vtimer_irq,
>  				    IRQCHIP_STATE_ACTIVE,
> @@ -535,27 +538,19 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
>  	set_cntvoff(0);
>  }
>  
> -static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
> +/*
> + * With a userspace irqchip we have to check if the guest de-asserted the
> + * timer and if so, unmask the timer irq signal on the host interrupt
> + * controller to ensure that we see future timer signals.
> + */
> +static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>  
>  	if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
> -		kvm_vtimer_update_mask_user(vcpu);
> -		return;
> -	}
> -
> -	/*
> -	 * If the guest disabled the timer without acking the interrupt, then
> -	 * we must make sure the physical and virtual active states are in
> -	 * sync by deactivating the physical interrupt, because otherwise we
> -	 * wouldn't see the next timer interrupt in the host.
> -	 */
> -	if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) {
> -		int ret;
> -		ret = irq_set_irqchip_state(host_vtimer_irq,
> -					    IRQCHIP_STATE_ACTIVE,
> -					    false);
> -		WARN_ON(ret);
> +		__timer_snapshot_state(vtimer);
> +		if (!kvm_timer_should_fire(vtimer))
> +			kvm_vtimer_update_mask_user(vcpu);
>  	}
>  }
>  
> @@ -568,21 +563,7 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
>   */
>  void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
>  {
> -	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> -
> -	/*
> -	 * If we entered the guest with the vtimer output asserted we have to
> -	 * check if the guest has modified the timer so that we should lower
> -	 * the line at this point.
> -	 */
> -	if (vtimer->irq.level) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -		if (!kvm_timer_should_fire(vtimer)) {
> -			kvm_timer_update_irq(vcpu, false, vtimer);
> -			unmask_vtimer_irq(vcpu);
> -		}
> -	}
> +	unmask_vtimer_irq_user(vcpu);
>  }
>  
>  int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
> @@ -813,6 +794,23 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
>  	return true;
>  }
>  
> +bool kvm_arch_timer_get_input_level(int vintid)
> +{
> +	struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
> +	struct arch_timer_context *timer;
> +
> +

extra blank line here

> +	if (vintid == vcpu_vtimer(vcpu)->irq.irq)
> +		timer = vcpu_vtimer(vcpu);
> +	else
> +		BUG(); /* We only map the vtimer so far */
> +
> +	if (timer->loaded)
> +		__timer_snapshot_state(timer);
> +
> +	return kvm_timer_should_fire(timer);
> +}
> +
>  int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -835,7 +833,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  	}
>  
>  	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
> -				    NULL);
> +				    kvm_arch_timer_get_input_level);
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.14.2
> 

[PATCH v5 7/8] KVM: arm/arm64: Provide a get_input_level for the arch timer

[Andrew Jones]

On Mon, Nov 20, 2017 at 08:16:48PM +0100, Christoffer Dall wrote:
> The VGIC can now support the life-cycle of mapped level-triggered
> interrupts, and we no longer have to read back the timer state on every
> exit from the VM if we had an asserted timer interrupt signal, because
> the VGIC already knows if we hit the unlikely case where the guest
> disables the timer without ACKing the virtual timer interrupt.
> 
> This means we rework a bit of the code to factor out the functionality
> to snapshot the timer state from vtimer_save_state(), and we can reuse
> this functionality in the sync path when we have an irqchip in
> userspace, and also to support our implementation of the
> get_input_level() function for the timer.
> 
> This change also means that we can no longer rely on the timer's view of
> the interrupt line to set the active state, because we no longer
> maintain this state for mapped interrupts when exiting from the guest.
> Instead, we only set the active state if the virtual interrupt is
> active, and otherwise we simply let the timer fire again and raise the
> virtual interrupt from the ISR.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  include/kvm/arm_arch_timer.h |  2 ++
>  virt/kvm/arm/arch_timer.c    | 76 +++++++++++++++++++++-----------------------
>  2 files changed, 39 insertions(+), 39 deletions(-)
> 
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index 6e45608b2399..b1dcfde0a3ef 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -90,6 +90,8 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
>  
>  void kvm_timer_init_vhe(void);
>  
> +bool kvm_arch_timer_get_input_level(int vintid);
> +
>  #define vcpu_vtimer(v)	(&(v)->arch.timer_cpu.vtimer)
>  #define vcpu_ptimer(v)	(&(v)->arch.timer_cpu.ptimer)
>  
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 8f804ba5896f..bcde6bb99669 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -343,6 +343,12 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
>  	phys_timer_emulate(vcpu);
>  }
>  
> +static void __timer_snapshot_state(struct arch_timer_context *timer)
> +{
> +	timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> +	timer->cnt_cval = read_sysreg_el0(cntv_cval);
> +}
> +
>  static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -354,10 +360,8 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
>  	if (!vtimer->loaded)
>  		goto out;
>  
> -	if (timer->enabled) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -	}
> +	if (timer->enabled)
> +		__timer_snapshot_state(vtimer);
>  
>  	/* Disable the virtual timer */
>  	write_sysreg_el0(0, cntv_ctl);
> @@ -454,8 +458,7 @@ static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
>  	bool phys_active;
>  	int ret;
>  
> -	phys_active = vtimer->irq.level ||
> -		      kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
> +	phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
>  
>  	ret = irq_set_irqchip_state(host_vtimer_irq,
>  				    IRQCHIP_STATE_ACTIVE,
> @@ -535,27 +538,19 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
>  	set_cntvoff(0);
>  }
>  
> -static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
> +/*
> + * With a userspace irqchip we have to check if the guest de-asserted the
> + * timer and if so, unmask the timer irq signal on the host interrupt
> + * controller to ensure that we see future timer signals.
> + */
> +static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>  
>  	if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
> -		kvm_vtimer_update_mask_user(vcpu);
> -		return;
> -	}
> -
> -	/*
> -	 * If the guest disabled the timer without acking the interrupt, then
> -	 * we must make sure the physical and virtual active states are in
> -	 * sync by deactivating the physical interrupt, because otherwise we
> -	 * wouldn't see the next timer interrupt in the host.
> -	 */
> -	if (!kvm_vgic_map_is_active(vcpu, vtimer->irq.irq)) {
> -		int ret;
> -		ret = irq_set_irqchip_state(host_vtimer_irq,
> -					    IRQCHIP_STATE_ACTIVE,
> -					    false);
> -		WARN_ON(ret);
> +		__timer_snapshot_state(vtimer);
> +		if (!kvm_timer_should_fire(vtimer))
> +			kvm_vtimer_update_mask_user(vcpu);
>  	}
>  }
>  
> @@ -568,21 +563,7 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu)
>   */
>  void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
>  {
> -	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> -
> -	/*
> -	 * If we entered the guest with the vtimer output asserted we have to
> -	 * check if the guest has modified the timer so that we should lower
> -	 * the line at this point.
> -	 */
> -	if (vtimer->irq.level) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
> -		if (!kvm_timer_should_fire(vtimer)) {
> -			kvm_timer_update_irq(vcpu, false, vtimer);
> -			unmask_vtimer_irq(vcpu);
> -		}
> -	}
> +	unmask_vtimer_irq_user(vcpu);
>  }
>  
>  int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
> @@ -813,6 +794,23 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
>  	return true;
>  }
>  
> +bool kvm_arch_timer_get_input_level(int vintid)
> +{
> +	struct kvm_vcpu *vcpu = kvm_arm_get_running_vcpu();
> +	struct arch_timer_context *timer;
> +
> +

extra blank line here

> +	if (vintid == vcpu_vtimer(vcpu)->irq.irq)
> +		timer = vcpu_vtimer(vcpu);
> +	else
> +		BUG(); /* We only map the vtimer so far */
> +
> +	if (timer->loaded)
> +		__timer_snapshot_state(timer);
> +
> +	return kvm_timer_should_fire(timer);
> +}
> +
>  int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  {
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
> @@ -835,7 +833,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
>  	}
>  
>  	ret = kvm_vgic_map_phys_irq(vcpu, host_vtimer_irq, vtimer->irq.irq,
> -				    NULL);
> +				    kvm_arch_timer_get_input_level);
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.14.2
> 

Re: [PATCH v5 1/8] KVM: arm/arm64: Remove redundant preemptible checks

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> The __this_cpu_read() and __this_cpu_write() functions already implement
> checks for the required preemption levels when using
> CONFIG_DEBUG_PREEMPT which gives you nice error messages and such.
> Therefore there is no need to explicitly check this using a BUG_ON() in
> the code (which we don't do for other uses of per cpu variables either).
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>


> ---
>  virt/kvm/arm/arm.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index c13d74c083fe..28548aeaf164 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -71,7 +71,6 @@ static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
>  
>  static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>  {
> -	BUG_ON(preemptible());
>  	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
>  }
>  
> @@ -81,7 +80,6 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>   */
>  struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
>  {
> -	BUG_ON(preemptible());
>  	return __this_cpu_read(kvm_arm_running_vcpu);
>  }
>  
> 

[PATCH v5 1/8] KVM: arm/arm64: Remove redundant preemptible checks

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> The __this_cpu_read() and __this_cpu_write() functions already implement
> checks for the required preemption levels when using
> CONFIG_DEBUG_PREEMPT which gives you nice error messages and such.
> Therefore there is no need to explicitly check this using a BUG_ON() in
> the code (which we don't do for other uses of per cpu variables either).
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>


> ---
>  virt/kvm/arm/arm.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index c13d74c083fe..28548aeaf164 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -71,7 +71,6 @@ static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
>  
>  static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>  {
> -	BUG_ON(preemptible());
>  	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
>  }
>  
> @@ -81,7 +80,6 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
>   */
>  struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
>  {
> -	BUG_ON(preemptible());
>  	return __this_cpu_read(kvm_arm_running_vcpu);
>  }
>  
> 

Re: [PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> We are about to distinguish between userspace accesses and mmio traps
> for a number of the mmio handlers.  When the requester vcpu is NULL, it
> mens we are handling a userspace acccess.
> 
> Factor out the functionality to get the request vcpu into its own
> function, mostly so we have a common place to document the semantics of
> the return value.
> 
> Also take the chance to move the functionality outside of holding a
> spinlock and instead explicitly disable and enable preemption.  This
> supports PREEMPT_RT kernels as well.
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
>  1 file changed, 27 insertions(+), 16 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index deb51ee16a3d..6113cf850f47 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  	return value;
>  }
>  
> +/*
> + * This function will return the VCPU that performed the MMIO access and
> + * trapped from twithin the VM, and will return NULL if this is a userspace
> + * access.
> + *
> + * We can disable preemption locally around accessing the per-CPU variable
> + * because even if the current thread is migrated to another CPU, reading the
> + * per-CPU value later will give us the same value as we update the per-CPU
> + * variable in the preempt notifier handlers.

This comment left me scratching my head a bit. Maybe you could change it
to point out that ... it's safe to *enable* preemption after the call
again, because of said reasons? Because disabling preemption before
accessing a per-CPU variable is not really an issue.

Apart from that it's fine.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> + */
> +static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
> +{
> +	struct kvm_vcpu *vcpu;
> +
> +	preempt_disable();
> +	vcpu = kvm_arm_get_running_vcpu();
> +	preempt_enable();
> +	return vcpu;
> +}
> +
>  void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
> @@ -184,24 +204,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
>  static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  				    bool new_active_state)
>  {
> -	struct kvm_vcpu *requester_vcpu;
>  	unsigned long flags;
> -	spin_lock_irqsave(&irq->irq_lock, flags);
> +	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
>  
> -	/*
> -	 * The vcpu parameter here can mean multiple things depending on how
> -	 * this function is called; when handling a trap from the kernel it
> -	 * depends on the GIC version, and these functions are also called as
> -	 * part of save/restore from userspace.
> -	 *
> -	 * Therefore, we have to figure out the requester in a reliable way.
> -	 *
> -	 * When accessing VGIC state from user space, the requester_vcpu is
> -	 * NULL, which is fine, because we guarantee that no VCPUs are running
> -	 * when accessing VGIC state from user space so irq->vcpu->cpu is
> -	 * always -1.
> -	 */
> -	requester_vcpu = kvm_arm_get_running_vcpu();
> +	spin_lock_irqsave(&irq->irq_lock, flags);
>  
>  	/*
>  	 * If this virtual IRQ was written into a list register, we
> @@ -213,6 +219,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  	 * vgic_change_active_prepare)  and still has to sync back this IRQ,
>  	 * so we release and re-acquire the spin_lock to let the other thread
>  	 * sync back the IRQ.
> +	 *
> +	 * When accessing VGIC state from user space, requester_vcpu is
> +	 * NULL, which is fine, because we guarantee that no VCPUs are running
> +	 * when accessing VGIC state from user space so irq->vcpu->cpu is
> +	 * always -1.
>  	 */
>  	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
>  	       irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
> 

[PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> We are about to distinguish between userspace accesses and mmio traps
> for a number of the mmio handlers.  When the requester vcpu is NULL, it
> mens we are handling a userspace acccess.
> 
> Factor out the functionality to get the request vcpu into its own
> function, mostly so we have a common place to document the semantics of
> the return value.
> 
> Also take the chance to move the functionality outside of holding a
> spinlock and instead explicitly disable and enable preemption.  This
> supports PREEMPT_RT kernels as well.
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
>  1 file changed, 27 insertions(+), 16 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index deb51ee16a3d..6113cf850f47 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  	return value;
>  }
>  
> +/*
> + * This function will return the VCPU that performed the MMIO access and
> + * trapped from twithin the VM, and will return NULL if this is a userspace
> + * access.
> + *
> + * We can disable preemption locally around accessing the per-CPU variable
> + * because even if the current thread is migrated to another CPU, reading the
> + * per-CPU value later will give us the same value as we update the per-CPU
> + * variable in the preempt notifier handlers.

This comment left me scratching my head a bit. Maybe you could change it
to point out that ... it's safe to *enable* preemption after the call
again, because of said reasons? Because disabling preemption before
accessing a per-CPU variable is not really an issue.

Apart from that it's fine.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> + */
> +static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
> +{
> +	struct kvm_vcpu *vcpu;
> +
> +	preempt_disable();
> +	vcpu = kvm_arm_get_running_vcpu();
> +	preempt_enable();
> +	return vcpu;
> +}
> +
>  void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
>  			      gpa_t addr, unsigned int len,
>  			      unsigned long val)
> @@ -184,24 +204,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
>  static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  				    bool new_active_state)
>  {
> -	struct kvm_vcpu *requester_vcpu;
>  	unsigned long flags;
> -	spin_lock_irqsave(&irq->irq_lock, flags);
> +	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
>  
> -	/*
> -	 * The vcpu parameter here can mean multiple things depending on how
> -	 * this function is called; when handling a trap from the kernel it
> -	 * depends on the GIC version, and these functions are also called as
> -	 * part of save/restore from userspace.
> -	 *
> -	 * Therefore, we have to figure out the requester in a reliable way.
> -	 *
> -	 * When accessing VGIC state from user space, the requester_vcpu is
> -	 * NULL, which is fine, because we guarantee that no VCPUs are running
> -	 * when accessing VGIC state from user space so irq->vcpu->cpu is
> -	 * always -1.
> -	 */
> -	requester_vcpu = kvm_arm_get_running_vcpu();
> +	spin_lock_irqsave(&irq->irq_lock, flags);
>  
>  	/*
>  	 * If this virtual IRQ was written into a list register, we
> @@ -213,6 +219,11 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
>  	 * vgic_change_active_prepare)  and still has to sync back this IRQ,
>  	 * so we release and re-acquire the spin_lock to let the other thread
>  	 * sync back the IRQ.
> +	 *
> +	 * When accessing VGIC state from user space, requester_vcpu is
> +	 * NULL, which is fine, because we guarantee that no VCPUs are running
> +	 * when accessing VGIC state from user space so irq->vcpu->cpu is
> +	 * always -1.
>  	 */
>  	while (irq->vcpu && /* IRQ may have state in an LR somewhere */
>  	       irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
> 

Re: [PATCH v5 3/8] KVM: arm/arm64: Don't cache the timer IRQ level

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> The timer was modeled after a strict idea of modelling an interrupt line
> level in software, meaning that only transitions in the level needed to
> be reported to the VGIC.  This works well for the timer, because the
> arch timer code is in complete control of the device and can track the
> transitions of the line.
> 
> However, as we are about to support using the HW bit in the VGIC not
> just for the timer, but also for VFIO which cannot track transitions of
> the interrupt line, we have to decide on an interface for level
> triggered mapped interrupts to the GIC, which both the timer and VFIO
> can use.
> 
> VFIO only sees an asserting transition of the physical interrupt line,
> and tells the VGIC when that happens.  That means that part of the
> interrupt flow is offloaded to the hardware.
> 
> To use the same interface for VFIO devices and the timer, we therefore
> have to change the timer (we cannot change VFIO because it doesn't know
> the details of the device it is assigning to a VM).
> 
> Luckily, changing the timer is simple, we just need to stop 'caching'
> the line level, but instead let the VGIC know the state of the timer
> every time there is a potential change in the line level, and when the
> line level should be asserted from the timer ISR.  The VGIC can ignore
> extra notifications using its validate mechanism.

Indeed vgic_validate_injection() should take care of that change.

> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> ---
>  virt/kvm/arm/arch_timer.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 190c99ed1b73..5f8ad8e3f3ff 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -99,11 +99,9 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
>  	}
>  	vtimer = vcpu_vtimer(vcpu);
>  
> -	if (!vtimer->irq.level) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		if (kvm_timer_irq_can_fire(vtimer))
> -			kvm_timer_update_irq(vcpu, true, vtimer);
> -	}
> +	vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> +	if (kvm_timer_irq_can_fire(vtimer))
> +		kvm_timer_update_irq(vcpu, true, vtimer);
>  
>  	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
>  		kvm_vtimer_update_mask_user(vcpu);
> @@ -324,12 +322,20 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>  	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>  	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
> +	bool level;
>  
>  	if (unlikely(!timer->enabled))
>  		return;
>  
> -	if (kvm_timer_should_fire(vtimer) != vtimer->irq.level)
> -		kvm_timer_update_irq(vcpu, !vtimer->irq.level, vtimer);
> +	/*
> +	 * The vtimer virtual interrupt is a 'mapped' interrupt, meaning part
> +	 * of its lifecycle is offloaded to the hardware, and we therefore may
> +	 * not have lowered the irq.level value before having to signal a new
> +	 * interrupt, but have to signal an interrupt every time the level is
> +	 * asserted.
> +	 */
> +	level = kvm_timer_should_fire(vtimer);
> +	kvm_timer_update_irq(vcpu, level, vtimer);
>  
>  	if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
>  		kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);
> 

[PATCH v5 3/8] KVM: arm/arm64: Don't cache the timer IRQ level

[Andre Przywara]

Hi,

On 20/11/17 19:16, Christoffer Dall wrote:
> The timer was modeled after a strict idea of modelling an interrupt line
> level in software, meaning that only transitions in the level needed to
> be reported to the VGIC.  This works well for the timer, because the
> arch timer code is in complete control of the device and can track the
> transitions of the line.
> 
> However, as we are about to support using the HW bit in the VGIC not
> just for the timer, but also for VFIO which cannot track transitions of
> the interrupt line, we have to decide on an interface for level
> triggered mapped interrupts to the GIC, which both the timer and VFIO
> can use.
> 
> VFIO only sees an asserting transition of the physical interrupt line,
> and tells the VGIC when that happens.  That means that part of the
> interrupt flow is offloaded to the hardware.
> 
> To use the same interface for VFIO devices and the timer, we therefore
> have to change the timer (we cannot change VFIO because it doesn't know
> the details of the device it is assigning to a VM).
> 
> Luckily, changing the timer is simple, we just need to stop 'caching'
> the line level, but instead let the VGIC know the state of the timer
> every time there is a potential change in the line level, and when the
> line level should be asserted from the timer ISR.  The VGIC can ignore
> extra notifications using its validate mechanism.

Indeed vgic_validate_injection() should take care of that change.

> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> ---
>  virt/kvm/arm/arch_timer.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 190c99ed1b73..5f8ad8e3f3ff 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -99,11 +99,9 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
>  	}
>  	vtimer = vcpu_vtimer(vcpu);
>  
> -	if (!vtimer->irq.level) {
> -		vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> -		if (kvm_timer_irq_can_fire(vtimer))
> -			kvm_timer_update_irq(vcpu, true, vtimer);
> -	}
> +	vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> +	if (kvm_timer_irq_can_fire(vtimer))
> +		kvm_timer_update_irq(vcpu, true, vtimer);
>  
>  	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
>  		kvm_vtimer_update_mask_user(vcpu);
> @@ -324,12 +322,20 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
>  	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>  	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
>  	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
> +	bool level;
>  
>  	if (unlikely(!timer->enabled))
>  		return;
>  
> -	if (kvm_timer_should_fire(vtimer) != vtimer->irq.level)
> -		kvm_timer_update_irq(vcpu, !vtimer->irq.level, vtimer);
> +	/*
> +	 * The vtimer virtual interrupt is a 'mapped' interrupt, meaning part
> +	 * of its lifecycle is offloaded to the hardware, and we therefore may
> +	 * not have lowered the irq.level value before having to signal a new
> +	 * interrupt, but have to signal an interrupt every time the level is
> +	 * asserted.
> +	 */
> +	level = kvm_timer_should_fire(vtimer);
> +	kvm_timer_update_irq(vcpu, level, vtimer);
>  
>  	if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
>  		kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);
> 

Re: [PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Christoffer Dall]

On Fri, Dec 01, 2017 at 06:04:32PM +0000, Andre Przywara wrote:
> Hi,
> 
> On 20/11/17 19:16, Christoffer Dall wrote:
> > We are about to distinguish between userspace accesses and mmio traps
> > for a number of the mmio handlers.  When the requester vcpu is NULL, it
> > mens we are handling a userspace acccess.
> > 
> > Factor out the functionality to get the request vcpu into its own
> > function, mostly so we have a common place to document the semantics of
> > the return value.
> > 
> > Also take the chance to move the functionality outside of holding a
> > spinlock and instead explicitly disable and enable preemption.  This
> > supports PREEMPT_RT kernels as well.
> > 
> > Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> >  virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
> >  1 file changed, 27 insertions(+), 16 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> > index deb51ee16a3d..6113cf850f47 100644
> > --- a/virt/kvm/arm/vgic/vgic-mmio.c
> > +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> > @@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
> >  	return value;
> >  }
> >  
> > +/*
> > + * This function will return the VCPU that performed the MMIO access and
> > + * trapped from twithin the VM, and will return NULL if this is a userspace
> > + * access.
> > + *
> > + * We can disable preemption locally around accessing the per-CPU variable
> > + * because even if the current thread is migrated to another CPU, reading the
> > + * per-CPU value later will give us the same value as we update the per-CPU
> > + * variable in the preempt notifier handlers.
> 
> This comment left me scratching my head a bit. Maybe you could change it
> to point out that ... it's safe to *enable* preemption after the call
> again, because of said reasons? Because disabling preemption before
> accessing a per-CPU variable is not really an issue.

I'll try to clarify.

> 
> Apart from that it's fine.
> 
> Reviewed-by: Andre Przywara <andre.przywara@arm.com>
> 
Thanks,
-Christoffer

[PATCH v5 2/8] KVM: arm/arm64: Factor out functionality to get vgic mmio requester_vcpu

[Christoffer Dall]

On Fri, Dec 01, 2017 at 06:04:32PM +0000, Andre Przywara wrote:
> Hi,
> 
> On 20/11/17 19:16, Christoffer Dall wrote:
> > We are about to distinguish between userspace accesses and mmio traps
> > for a number of the mmio handlers.  When the requester vcpu is NULL, it
> > mens we are handling a userspace acccess.
> > 
> > Factor out the functionality to get the request vcpu into its own
> > function, mostly so we have a common place to document the semantics of
> > the return value.
> > 
> > Also take the chance to move the functionality outside of holding a
> > spinlock and instead explicitly disable and enable preemption.  This
> > supports PREEMPT_RT kernels as well.
> > 
> > Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> >  virt/kvm/arm/vgic/vgic-mmio.c | 43 +++++++++++++++++++++++++++----------------
> >  1 file changed, 27 insertions(+), 16 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> > index deb51ee16a3d..6113cf850f47 100644
> > --- a/virt/kvm/arm/vgic/vgic-mmio.c
> > +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> > @@ -122,6 +122,26 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
> >  	return value;
> >  }
> >  
> > +/*
> > + * This function will return the VCPU that performed the MMIO access and
> > + * trapped from twithin the VM, and will return NULL if this is a userspace
> > + * access.
> > + *
> > + * We can disable preemption locally around accessing the per-CPU variable
> > + * because even if the current thread is migrated to another CPU, reading the
> > + * per-CPU value later will give us the same value as we update the per-CPU
> > + * variable in the preempt notifier handlers.
> 
> This comment left me scratching my head a bit. Maybe you could change it
> to point out that ... it's safe to *enable* preemption after the call
> again, because of said reasons? Because disabling preemption before
> accessing a per-CPU variable is not really an issue.

I'll try to clarify.

> 
> Apart from that it's fine.
> 
> Reviewed-by: Andre Przywara <andre.przywara@arm.com>
> 
Thanks,
-Christoffer

Re: [PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Christoffer Dall]

On Wed, Nov 29, 2017 at 04:13:14PM +0100, Andrew Jones wrote:
> On Mon, Nov 20, 2017 at 08:16:47PM +0100, Christoffer Dall wrote:
> > For mapped IRQs (with the HW bit set in the LR) we have to follow some
> > rules of the architecture.  One of these rules is that VM must not be
> > allowed to deactivate a virtual interrupt with the HW bit set unless the
> > physical interrupt is also active.
> > 
> > This works fine when injecting mapped interrupts, because we leave it up
> > to the injector to either set EOImode==1 or manually set the active
> > state of the physical interrupt.
> > 
> > However, the guest can set virtual interrupt to be pending or active by
> > writing to the virtual distributor, which could lead to deactivating a
> > virtual interrupt with the HW bit set without the physical interrupt
> > being active.
> > 
> > We could set the physical interrupt to active whenever we are about to
> > enter the VM with a HW interrupt either pending or active, but that
> > would be really slow, especially on GICv2.  So we take the long way
> > around and do the hard work when needed, which is expected to be
> > extremely rare.
> > 
> > When the VM sets the pending state for a HW interrupt on the virtual
> > distributor we set the active state on the physical distributor, because
> > the virtual interrupt can become active and then the guest can
> > deactivate it.
> > 
> > When the VM clears the pending state we also clear it on the physical
> > side, because the injector might otherwise raise the interrupt.  We also
> > clear the physical active state when the virtual interrupt is not
> > active, since otherwise a SPEND/CPEND sequence from the guest would
> > prevent signaling of future interrupts.
> > 
> > Changing the state of mapped interrupts from userspace is not supported,
> > and it's expected that userspace unmaps devices from VFIO before
> > attempting to set the interrupt state, because the interrupt state is
> > driven by hardware.
> > 
> > Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> >  virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
> >  virt/kvm/arm/vgic/vgic.c      |  7 +++++
> >  virt/kvm/arm/vgic/vgic.h      |  1 +
> >  3 files changed, 73 insertions(+), 6 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> > index 6113cf850f47..294e949ece24 100644
> > --- a/virt/kvm/arm/vgic/vgic-mmio.c
> > +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> > @@ -16,6 +16,7 @@
> >  #include <linux/kvm.h>
> >  #include <linux/kvm_host.h>
> >  #include <kvm/iodev.h>
> > +#include <kvm/arm_arch_timer.h>
> >  #include <kvm/arm_vgic.h>
> >  
> >  #include "vgic.h"
> > @@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
> >  	return vcpu;
> >  }
> >  
> > +/* Must be called with irq->irq_lock held */
> > +static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> > +				 bool is_uaccess)
> > +{
> > +	if (!is_uaccess)
> > +		irq->pending_latch = true;
> > +
> > +	if (!is_uaccess)
> > +		vgic_irq_set_phys_active(irq, true);
> 
> I see this whole patch has this two 'if (!is_uaccess)' checks pattern.
> Is that meant to convey something? 

Yeah, that I'm a fool.

> Or is the first condition not supposed
> to have the '!'? (I'm lost with regards to the state tracking differences
> between the guest and userspace and just reviewing superficially...)
> 

This became weird becaus the first clause used to be "if (!is_uaccess ||
is_timer)", but now when the timer is interrupt driven (the timer
optimization series), we don't have that concept anymore, and I just
blindly removes the "|| is_timer" part.

I reworked this so that the functions now have

	if (is_uaccess)
		return;


Thanks,
-Christoffer

[PATCH v5 6/8] KVM: arm/arm64: Support VGIC dist pend/active changes for mapped IRQs

[Christoffer Dall]

On Wed, Nov 29, 2017 at 04:13:14PM +0100, Andrew Jones wrote:
> On Mon, Nov 20, 2017 at 08:16:47PM +0100, Christoffer Dall wrote:
> > For mapped IRQs (with the HW bit set in the LR) we have to follow some
> > rules of the architecture.  One of these rules is that VM must not be
> > allowed to deactivate a virtual interrupt with the HW bit set unless the
> > physical interrupt is also active.
> > 
> > This works fine when injecting mapped interrupts, because we leave it up
> > to the injector to either set EOImode==1 or manually set the active
> > state of the physical interrupt.
> > 
> > However, the guest can set virtual interrupt to be pending or active by
> > writing to the virtual distributor, which could lead to deactivating a
> > virtual interrupt with the HW bit set without the physical interrupt
> > being active.
> > 
> > We could set the physical interrupt to active whenever we are about to
> > enter the VM with a HW interrupt either pending or active, but that
> > would be really slow, especially on GICv2.  So we take the long way
> > around and do the hard work when needed, which is expected to be
> > extremely rare.
> > 
> > When the VM sets the pending state for a HW interrupt on the virtual
> > distributor we set the active state on the physical distributor, because
> > the virtual interrupt can become active and then the guest can
> > deactivate it.
> > 
> > When the VM clears the pending state we also clear it on the physical
> > side, because the injector might otherwise raise the interrupt.  We also
> > clear the physical active state when the virtual interrupt is not
> > active, since otherwise a SPEND/CPEND sequence from the guest would
> > prevent signaling of future interrupts.
> > 
> > Changing the state of mapped interrupts from userspace is not supported,
> > and it's expected that userspace unmaps devices from VFIO before
> > attempting to set the interrupt state, because the interrupt state is
> > driven by hardware.
> > 
> > Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> >  virt/kvm/arm/vgic/vgic-mmio.c | 71 +++++++++++++++++++++++++++++++++++++++----
> >  virt/kvm/arm/vgic/vgic.c      |  7 +++++
> >  virt/kvm/arm/vgic/vgic.h      |  1 +
> >  3 files changed, 73 insertions(+), 6 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> > index 6113cf850f47..294e949ece24 100644
> > --- a/virt/kvm/arm/vgic/vgic-mmio.c
> > +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> > @@ -16,6 +16,7 @@
> >  #include <linux/kvm.h>
> >  #include <linux/kvm_host.h>
> >  #include <kvm/iodev.h>
> > +#include <kvm/arm_arch_timer.h>
> >  #include <kvm/arm_vgic.h>
> >  
> >  #include "vgic.h"
> > @@ -142,10 +143,22 @@ static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
> >  	return vcpu;
> >  }
> >  
> > +/* Must be called with irq->irq_lock held */
> > +static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> > +				 bool is_uaccess)
> > +{
> > +	if (!is_uaccess)
> > +		irq->pending_latch = true;
> > +
> > +	if (!is_uaccess)
> > +		vgic_irq_set_phys_active(irq, true);
> 
> I see this whole patch has this two 'if (!is_uaccess)' checks pattern.
> Is that meant to convey something? 

Yeah, that I'm a fool.

> Or is the first condition not supposed
> to have the '!'? (I'm lost with regards to the state tracking differences
> between the guest and userspace and just reviewing superficially...)
> 

This became weird becaus the first clause used to be "if (!is_uaccess ||
is_timer)", but now when the timer is interrupt driven (the timer
optimization series), we don't have that concept anymore, and I just
blindly removes the "|| is_timer" part.

I reworked this so that the functions now have

	if (is_uaccess)
		return;


Thanks,
-Christoffer