[GIT PULL] KVM/arm updates for 5.3-rc4

[GIT PULL] KVM/arm updates for 5.3-rc4

[Marc Zyngier]

Paolo, Radim,

Here's a set of update for -rc4. Yet another reset fix, and two subtle
VGIC fixes for issues that can be observed in interesting corner cases.

Note that this is on top of kvmarm-fixes-for-5.3[1], which hasn't been
pulled yet. Hopefully you can pull both at the same time!

Thanks,

	M.

[1] https://lore.kernel.org/kvmarm/20190731173650.12627-1-maz@kernel.org

The following changes since commit cdb2d3ee0436d74fa9092f2df46aaa6f9e03c969:

  arm64: KVM: hyp: debug-sr: Mark expected switch fall-through (2019-07-29 11:01:37 +0100)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-for-5.3-2

for you to fetch changes up to 16e604a437c89751dc626c9e90cf88ba93c5be64:

  KVM: arm/arm64: vgic: Reevaluate level sensitive interrupts on enable (2019-08-09 08:07:26 +0100)

----------------------------------------------------------------
KVM/arm fixes for 5.3, take #2

- Fix our system register reset so that we stop writing
  non-sensical values to them, and track which registers
  get reset instead.
- Sync VMCR back from the GIC on WFI so that KVM has an
  exact vue of PMR.
- Reevaluate state of HW-mapped, level triggered interrupts
  on enable.

----------------------------------------------------------------
Alexandru Elisei (1):
      KVM: arm/arm64: vgic: Reevaluate level sensitive interrupts on enable

Marc Zyngier (3):
      KVM: arm/arm64: Sync ICH_VMCR_EL2 back when about to block
      KVM: arm64: Don't write junk to sysregs on reset
      KVM: arm: Don't write junk to CP15 registers on reset

 arch/arm/kvm/coproc.c         | 23 +++++++++++++++--------
 arch/arm64/kvm/sys_regs.c     | 32 ++++++++++++++++++--------------
 include/kvm/arm_vgic.h        |  1 +
 virt/kvm/arm/arm.c            | 11 +++++++++++
 virt/kvm/arm/vgic/vgic-mmio.c | 16 ++++++++++++++++
 virt/kvm/arm/vgic/vgic-v2.c   |  9 ++++++++-
 virt/kvm/arm/vgic/vgic-v3.c   |  7 ++++++-
 virt/kvm/arm/vgic/vgic.c      | 11 +++++++++++
 virt/kvm/arm/vgic/vgic.h      |  2 ++
 9 files changed, 88 insertions(+), 24 deletions(-)

[PATCH 1/4] KVM: arm/arm64: Sync ICH_VMCR_EL2 back when about to block

[Marc Zyngier]

Since commit commit 328e56647944 ("KVM: arm/arm64: vgic: Defer
touching GICH_VMCR to vcpu_load/put"), we leave ICH_VMCR_EL2 (or
its GICv2 equivalent) loaded as long as we can, only syncing it
back when we're scheduled out.

There is a small snag with that though: kvm_vgic_vcpu_pending_irq(),
which is indirectly called from kvm_vcpu_check_block(), needs to
evaluate the guest's view of ICC_PMR_EL1. At the point were we
call kvm_vcpu_check_block(), the vcpu is still loaded, and whatever
changes to PMR is not visible in memory until we do a vcpu_put().

Things go really south if the guest does the following:

	mov x0, #0	// or any small value masking interrupts
	msr ICC_PMR_EL1, x0

	[vcpu preempted, then rescheduled, VMCR sampled]

	mov x0, #ff	// allow all interrupts
	msr ICC_PMR_EL1, x0
	wfi		// traps to EL2, so samping of VMCR

	[interrupt arrives just after WFI]

Here, the hypervisor's view of PMR is zero, while the guest has enabled
its interrupts. kvm_vgic_vcpu_pending_irq() will then say that no
interrupts are pending (despite an interrupt being received) and we'll
block for no reason. If the guest doesn't have a periodic interrupt
firing once it has blocked, it will stay there forever.

To avoid this unfortuante situation, let's resync VMCR from
kvm_arch_vcpu_blocking(), ensuring that a following kvm_vcpu_check_block()
will observe the latest value of PMR.

This has been found by booting an arm64 Linux guest with the pseudo NMI
feature, and thus using interrupt priorities to mask interrupts instead
of the usual PSTATE masking.

Cc: stable@vger.kernel.org # 4.12
Fixes: 328e56647944 ("KVM: arm/arm64: vgic: Defer touching GICH_VMCR to vcpu_load/put")
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 include/kvm/arm_vgic.h      |  1 +
 virt/kvm/arm/arm.c          | 11 +++++++++++
 virt/kvm/arm/vgic/vgic-v2.c |  9 ++++++++-
 virt/kvm/arm/vgic/vgic-v3.c |  7 ++++++-
 virt/kvm/arm/vgic/vgic.c    | 11 +++++++++++
 virt/kvm/arm/vgic/vgic.h    |  2 ++
 6 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 46bbc949c20a..7a30524a80ee 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -350,6 +350,7 @@ int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
 
 void kvm_vgic_load(struct kvm_vcpu *vcpu);
 void kvm_vgic_put(struct kvm_vcpu *vcpu);
+void kvm_vgic_vmcr_sync(struct kvm_vcpu *vcpu);
 
 #define irqchip_in_kernel(k)	(!!((k)->arch.vgic.in_kernel))
 #define vgic_initialized(k)	((k)->arch.vgic.initialized)
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index c704fa696184..482b20256fa8 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -323,6 +323,17 @@ int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
 {
+	/*
+	 * If we're about to block (most likely because we've just hit a
+	 * WFI), we need to sync back the state of the GIC CPU interface
+	 * so that we have the lastest PMR and group enables. This ensures
+	 * that kvm_arch_vcpu_runnable has up-to-date data to decide
+	 * whether we have pending interrupts.
+	 */
+	preempt_disable();
+	kvm_vgic_vmcr_sync(vcpu);
+	preempt_enable();
+
 	kvm_vgic_v4_enable_doorbell(vcpu);
 }
 
diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index 6dd5ad706c92..96aab77d0471 100644
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -484,10 +484,17 @@ void vgic_v2_load(struct kvm_vcpu *vcpu)
 		       kvm_vgic_global_state.vctrl_base + GICH_APR);
 }
 
-void vgic_v2_put(struct kvm_vcpu *vcpu)
+void vgic_v2_vmcr_sync(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v2_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v2;
 
 	cpu_if->vgic_vmcr = readl_relaxed(kvm_vgic_global_state.vctrl_base + GICH_VMCR);
+}
+
+void vgic_v2_put(struct kvm_vcpu *vcpu)
+{
+	struct vgic_v2_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v2;
+
+	vgic_v2_vmcr_sync(vcpu);
 	cpu_if->vgic_apr = readl_relaxed(kvm_vgic_global_state.vctrl_base + GICH_APR);
 }
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index c2c9ce009f63..0c653a1e5215 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -662,12 +662,17 @@ void vgic_v3_load(struct kvm_vcpu *vcpu)
 		__vgic_v3_activate_traps(vcpu);
 }
 
-void vgic_v3_put(struct kvm_vcpu *vcpu)
+void vgic_v3_vmcr_sync(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
 
 	if (likely(cpu_if->vgic_sre))
 		cpu_if->vgic_vmcr = kvm_call_hyp_ret(__vgic_v3_read_vmcr);
+}
+
+void vgic_v3_put(struct kvm_vcpu *vcpu)
+{
+	vgic_v3_vmcr_sync(vcpu);
 
 	kvm_call_hyp(__vgic_v3_save_aprs, vcpu);
 
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 04786c8ec77e..13d4b38a94ec 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -919,6 +919,17 @@ void kvm_vgic_put(struct kvm_vcpu *vcpu)
 		vgic_v3_put(vcpu);
 }
 
+void kvm_vgic_vmcr_sync(struct kvm_vcpu *vcpu)
+{
+	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
+		return;
+
+	if (kvm_vgic_global_state.type == VGIC_V2)
+		vgic_v2_vmcr_sync(vcpu);
+	else
+		vgic_v3_vmcr_sync(vcpu);
+}
+
 int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 57205beaa981..11adbdac1d56 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -193,6 +193,7 @@ int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
 void vgic_v2_init_lrs(void);
 void vgic_v2_load(struct kvm_vcpu *vcpu);
 void vgic_v2_put(struct kvm_vcpu *vcpu);
+void vgic_v2_vmcr_sync(struct kvm_vcpu *vcpu);
 
 void vgic_v2_save_state(struct kvm_vcpu *vcpu);
 void vgic_v2_restore_state(struct kvm_vcpu *vcpu);
@@ -223,6 +224,7 @@ bool vgic_v3_check_base(struct kvm *kvm);
 
 void vgic_v3_load(struct kvm_vcpu *vcpu);
 void vgic_v3_put(struct kvm_vcpu *vcpu);
+void vgic_v3_vmcr_sync(struct kvm_vcpu *vcpu);
 
 bool vgic_has_its(struct kvm *kvm);
 int kvm_vgic_register_its_device(void);
-- 
2.20.1

[PATCH 2/4] KVM: arm64: Don't write junk to sysregs on reset

[Marc Zyngier]

At the moment, the way we reset system registers is mildly insane:
We write junk to them, call the reset functions, and then check that
we have something else in them.

The "fun" thing is that this can happen while the guest is running
(PSCI, for example). If anything in KVM has to evaluate the state
of a system register while junk is in there, bad thing may happen.

Let's stop doing that. Instead, we track that we have called a
reset function for that register, and assume that the reset
function has done something. This requires fixing a couple of
sysreg refinition in the trap table.

In the end, the very need of this reset check is pretty dubious,
as it doesn't check everything (a lot of the sysregs leave outside of
the sys_regs[] array). It may well be axed in the near future.

Tested-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f26e181d881c..2071260a275b 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -632,7 +632,7 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 	 */
 	val = ((pmcr & ~ARMV8_PMU_PMCR_MASK)
 	       | (ARMV8_PMU_PMCR_MASK & 0xdecafbad)) & (~ARMV8_PMU_PMCR_E);
-	__vcpu_sys_reg(vcpu, PMCR_EL0) = val;
+	__vcpu_sys_reg(vcpu, r->reg) = val;
 }
 
 static bool check_pmu_access_disabled(struct kvm_vcpu *vcpu, u64 flags)
@@ -981,13 +981,13 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
 #define DBG_BCR_BVR_WCR_WVR_EL1(n)					\
 	{ SYS_DESC(SYS_DBGBVRn_EL1(n)),					\
-	  trap_bvr, reset_bvr, n, 0, get_bvr, set_bvr },		\
+	  trap_bvr, reset_bvr, 0, 0, get_bvr, set_bvr },		\
 	{ SYS_DESC(SYS_DBGBCRn_EL1(n)),					\
-	  trap_bcr, reset_bcr, n, 0, get_bcr, set_bcr },		\
+	  trap_bcr, reset_bcr, 0, 0, get_bcr, set_bcr },		\
 	{ SYS_DESC(SYS_DBGWVRn_EL1(n)),					\
-	  trap_wvr, reset_wvr, n, 0,  get_wvr, set_wvr },		\
+	  trap_wvr, reset_wvr, 0, 0,  get_wvr, set_wvr },		\
 	{ SYS_DESC(SYS_DBGWCRn_EL1(n)),					\
-	  trap_wcr, reset_wcr, n, 0,  get_wcr, set_wcr }
+	  trap_wcr, reset_wcr, 0, 0,  get_wcr, set_wcr }
 
 /* Macro to expand the PMEVCNTRn_EL0 register */
 #define PMU_PMEVCNTR_EL0(n)						\
@@ -1540,7 +1540,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
 	{ SYS_DESC(SYS_CTR_EL0), access_ctr },
 
-	{ SYS_DESC(SYS_PMCR_EL0), access_pmcr, reset_pmcr, },
+	{ SYS_DESC(SYS_PMCR_EL0), access_pmcr, reset_pmcr, PMCR_EL0 },
 	{ SYS_DESC(SYS_PMCNTENSET_EL0), access_pmcnten, reset_unknown, PMCNTENSET_EL0 },
 	{ SYS_DESC(SYS_PMCNTENCLR_EL0), access_pmcnten, NULL, PMCNTENSET_EL0 },
 	{ SYS_DESC(SYS_PMOVSCLR_EL0), access_pmovs, NULL, PMOVSSET_EL0 },
@@ -2254,13 +2254,19 @@ static int emulate_sys_reg(struct kvm_vcpu *vcpu,
 }
 
 static void reset_sys_reg_descs(struct kvm_vcpu *vcpu,
-			      const struct sys_reg_desc *table, size_t num)
+				const struct sys_reg_desc *table, size_t num,
+				unsigned long *bmap)
 {
 	unsigned long i;
 
 	for (i = 0; i < num; i++)
-		if (table[i].reset)
+		if (table[i].reset) {
+			int reg = table[i].reg;
+
 			table[i].reset(vcpu, &table[i]);
+			if (reg > 0 && reg < NR_SYS_REGS)
+				set_bit(reg, bmap);
+		}
 }
 
 /**
@@ -2774,18 +2780,16 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
 {
 	size_t num;
 	const struct sys_reg_desc *table;
-
-	/* Catch someone adding a register without putting in reset entry. */
-	memset(&vcpu->arch.ctxt.sys_regs, 0x42, sizeof(vcpu->arch.ctxt.sys_regs));
+	DECLARE_BITMAP(bmap, NR_SYS_REGS) = { 0, };
 
 	/* Generic chip reset first (so target could override). */
-	reset_sys_reg_descs(vcpu, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+	reset_sys_reg_descs(vcpu, sys_reg_descs, ARRAY_SIZE(sys_reg_descs), bmap);
 
 	table = get_target_table(vcpu->arch.target, true, &num);
-	reset_sys_reg_descs(vcpu, table, num);
+	reset_sys_reg_descs(vcpu, table, num, bmap);
 
 	for (num = 1; num < NR_SYS_REGS; num++) {
-		if (WARN(__vcpu_sys_reg(vcpu, num) == 0x4242424242424242,
+		if (WARN(!test_bit(num, bmap),
 			 "Didn't reset __vcpu_sys_reg(%zi)\n", num))
 			break;
 	}
-- 
2.20.1

[PATCH 3/4] KVM: arm: Don't write junk to CP15 registers on reset

[Marc Zyngier]

At the moment, the way we reset CP15 registers is mildly insane:
We write junk to them, call the reset functions, and then check that
we have something else in them.

The "fun" thing is that this can happen while the guest is running
(PSCI, for example). If anything in KVM has to evaluate the state
of a CP15 register while junk is in there, bad thing may happen.

Let's stop doing that. Instead, we track that we have called a
reset function for that register, and assume that the reset
function has done something.

In the end, the very need of this reset check is pretty dubious,
as it doesn't check everything (a lot of the CP15 reg leave outside
of the cp15_regs[] array). It may well be axed in the near future.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm/kvm/coproc.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index d2806bcff8bb..07745ee022a1 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c
@@ -651,13 +651,22 @@ int kvm_handle_cp14_64(struct kvm_vcpu *vcpu, struct kvm_run *run)
 }
 
 static void reset_coproc_regs(struct kvm_vcpu *vcpu,
-			      const struct coproc_reg *table, size_t num)
+			      const struct coproc_reg *table, size_t num,
+			      unsigned long *bmap)
 {
 	unsigned long i;
 
 	for (i = 0; i < num; i++)
-		if (table[i].reset)
+		if (table[i].reset) {
+			int reg = table[i].reg;
+
 			table[i].reset(vcpu, &table[i]);
+			if (reg > 0 && reg < NR_CP15_REGS) {
+				set_bit(reg, bmap);
+				if (table[i].is_64bit)
+					set_bit(reg + 1, bmap);
+			}
+		}
 }
 
 static struct coproc_params decode_32bit_hsr(struct kvm_vcpu *vcpu)
@@ -1432,17 +1441,15 @@ void kvm_reset_coprocs(struct kvm_vcpu *vcpu)
 {
 	size_t num;
 	const struct coproc_reg *table;
-
-	/* Catch someone adding a register without putting in reset entry. */
-	memset(vcpu->arch.ctxt.cp15, 0x42, sizeof(vcpu->arch.ctxt.cp15));
+	DECLARE_BITMAP(bmap, NR_CP15_REGS) = { 0, };
 
 	/* Generic chip reset first (so target could override). */
-	reset_coproc_regs(vcpu, cp15_regs, ARRAY_SIZE(cp15_regs));
+	reset_coproc_regs(vcpu, cp15_regs, ARRAY_SIZE(cp15_regs), bmap);
 
 	table = get_target_table(vcpu->arch.target, &num);
-	reset_coproc_regs(vcpu, table, num);
+	reset_coproc_regs(vcpu, table, num, bmap);
 
 	for (num = 1; num < NR_CP15_REGS; num++)
-		WARN(vcpu_cp15(vcpu, num) == 0x42424242,
+		WARN(!test_bit(num, bmap),
 		     "Didn't reset vcpu_cp15(vcpu, %zi)", num);
 }
-- 
2.20.1

[PATCH 4/4] KVM: arm/arm64: vgic: Reevaluate level sensitive interrupts on enable

[Marc Zyngier]

From: Alexandru Elisei <alexandru.elisei@arm.com>

A HW mapped level sensitive interrupt asserted by a device will not be put
into the ap_list if it is disabled at the VGIC level. When it is enabled
again, it will be inserted into the ap_list and written to a list register
on guest entry regardless of the state of the device.

We could argue that this can also happen on real hardware, when the command
to enable the interrupt reached the GIC before the device had the chance to
de-assert the interrupt signal; however, we emulate the distributor and
redistributors in software and we can do better than that.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 virt/kvm/arm/vgic/vgic-mmio.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 3ba7278fb533..44efc2ff863f 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -113,6 +113,22 @@ void vgic_mmio_write_senable(struct kvm_vcpu *vcpu,
 		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
 
 		raw_spin_lock_irqsave(&irq->irq_lock, flags);
+		if (vgic_irq_is_mapped_level(irq)) {
+			bool was_high = irq->line_level;
+
+			/*
+			 * We need to update the state of the interrupt because
+			 * the guest might have changed the state of the device
+			 * while the interrupt was disabled at the VGIC level.
+			 */
+			irq->line_level = vgic_get_phys_line_level(irq);
+			/*
+			 * Deactivate the physical interrupt so the GIC will let
+			 * us know when it is asserted again.
+			 */
+			if (!irq->active && was_high && !irq->line_level)
+				vgic_irq_set_phys_active(irq, false);
+		}
 		irq->enabled = true;
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 
-- 
2.20.1

Re: [GIT PULL] KVM/arm updates for 5.3-rc4

[Paolo Bonzini]

On 09/08/19 09:48, Marc Zyngier wrote:
>   git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-for-5.3
>   git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-for-5.3-2

Pulled both.  Thank you for including the lore link to the 5.3-rc3 pull
request.

Paolo