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* [PATCH RFC 00/15] KVM: Dirty ring interface
@ 2019-11-29 21:32 Peter Xu
  2019-11-29 21:32 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
  0 siblings, 1 reply; 7+ messages in thread
From: Peter Xu @ 2019-11-29 21:32 UTC (permalink / raw)
  To: linux-kernel, kvm
  Cc: Paolo Bonzini, Cao Lei, peterx, Dr . David Alan Gilbert,
	Sean Christopherson, Vitaly Kuznetsov

Branch is here: https://github.com/xzpeter/linux/tree/kvm-dirty-ring

Overview
============

This is a continued work from Lei Cao <lei.cao@stratus.com> and Paolo
on the KVM dirty ring interface.  To make it simple, I'll still start
with version 1 as RFC.

The new dirty ring interface is another way to collect dirty pages for
the virtual machine, but it is different from the existing dirty
logging interface in a few ways, majorly:

  - Data format: The dirty data was in a ring format rather than a
    bitmap format, so the size of data to sync for dirty logging does
    not depend on the size of guest memory any more, but speed of
    dirtying.  Also, the dirty ring is per-vcpu (currently plus
    another per-vm ring, so total ring number is N+1), while the dirty
    bitmap is per-vm.

  - Data copy: The sync of dirty pages does not need data copy any more,
    but instead the ring is shared between the userspace and kernel by
    page sharings (mmap() on either the vm fd or vcpu fd)

  - Interface: Instead of using the old KVM_GET_DIRTY_LOG,
    KVM_CLEAR_DIRTY_LOG interfaces, the new ring uses a new interface
    called KVM_RESET_DIRTY_RINGS when we want to reset the collected
    dirty pages to protected mode again (works like
    KVM_CLEAR_DIRTY_LOG, but ring based)

And more.

I would appreciate if the reviewers can start with patch "KVM:
Implement ring-based dirty memory tracking", especially the document
update part for the big picture.  Then I'll avoid copying into most of
them into cover letter again.

I marked this series as RFC because I'm at least uncertain on this
change of vcpu_enter_guest():

        if (kvm_check_request(KVM_REQ_DIRTY_RING_FULL, vcpu)) {
                vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
                /*
                        * If this is requested, it means that we've
                        * marked the dirty bit in the dirty ring BUT
                        * we've not written the date.  Do it now.
                        */
                r = kvm_emulate_instruction(vcpu, 0);
                r = r >= 0 ? 0 : r;
                goto out;
        }

I did a kvm_emulate_instruction() when dirty ring reaches softlimit
and want to exit to userspace, however I'm not really sure whether
there could have any side effect.  I'd appreciate any comment of
above, or anything else.

Tests
===========

I wanted to continue work on the QEMU part, but after I noticed that
the interface might still prone to change, I posted this series first.
However to make sure it's at least working, I've provided unit tests
together with the series.  The unit tests should be able to test the
series in at least three major paths:

  (1) ./dirty_log_test -M dirty-ring

      This tests async ring operations: this should be the major work
      mode for the dirty ring interface, say, when the kernel is
      queuing more data, the userspace is collecting too.  Ring can
      hardly reaches full when working like this, because in most
      cases the collection could be fast.

  (2) ./dirty_log_test -M dirty-ring -c 1024

      This set the ring size to be very small so that ring soft-full
      always triggers (soft-full is a soft limit of the ring state,
      when the dirty ring reaches the soft limit it'll do a userspace
      exit and let the userspace to collect the data).

  (3) ./dirty_log_test -M dirty-ring-wait-queue

      This sololy test the extreme case where ring is full.  When the
      ring is completely full, the thread (no matter vcpu or not) will
      be put onto a per-vm waitqueue, and KVM_RESET_DIRTY_RINGS will
      wake the threads up (assuming until which the ring will not be
      full any more).

Thanks,

Cao, Lei (2):
  KVM: Add kvm/vcpu argument to mark_dirty_page_in_slot
  KVM: X86: Implement ring-based dirty memory tracking

Paolo Bonzini (1):
  KVM: Move running VCPU from ARM to common code

Peter Xu (12):
  KVM: Add build-time error check on kvm_run size
  KVM: Implement ring-based dirty memory tracking
  KVM: Make dirty ring exclusive to dirty bitmap log
  KVM: Introduce dirty ring wait queue
  KVM: selftests: Always clear dirty bitmap after iteration
  KVM: selftests: Sync uapi/linux/kvm.h to tools/
  KVM: selftests: Use a single binary for dirty/clear log test
  KVM: selftests: Introduce after_vcpu_run hook for dirty log test
  KVM: selftests: Add dirty ring buffer test
  KVM: selftests: Let dirty_log_test async for dirty ring test
  KVM: selftests: Add "-c" parameter to dirty log test
  KVM: selftests: Test dirty ring waitqueue

 Documentation/virt/kvm/api.txt                | 116 +++++
 arch/arm/include/asm/kvm_host.h               |   2 -
 arch/arm64/include/asm/kvm_host.h             |   2 -
 arch/x86/include/asm/kvm_host.h               |   5 +
 arch/x86/include/uapi/asm/kvm.h               |   1 +
 arch/x86/kvm/Makefile                         |   3 +-
 arch/x86/kvm/mmu/mmu.c                        |   6 +
 arch/x86/kvm/vmx/vmx.c                        |   7 +
 arch/x86/kvm/x86.c                            |  12 +
 include/linux/kvm_dirty_ring.h                |  67 +++
 include/linux/kvm_host.h                      |  37 ++
 include/linux/kvm_types.h                     |   1 +
 include/uapi/linux/kvm.h                      |  36 ++
 tools/include/uapi/linux/kvm.h                |  47 ++
 tools/testing/selftests/kvm/Makefile          |   2 -
 .../selftests/kvm/clear_dirty_log_test.c      |   2 -
 tools/testing/selftests/kvm/dirty_log_test.c  | 452 ++++++++++++++++--
 .../testing/selftests/kvm/include/kvm_util.h  |   6 +
 tools/testing/selftests/kvm/lib/kvm_util.c    | 103 ++++
 .../selftests/kvm/lib/kvm_util_internal.h     |   5 +
 virt/kvm/arm/arm.c                            |  29 --
 virt/kvm/arm/perf.c                           |   6 +-
 virt/kvm/arm/vgic/vgic-mmio.c                 |  15 +-
 virt/kvm/dirty_ring.c                         | 156 ++++++
 virt/kvm/kvm_main.c                           | 315 +++++++++++-
 25 files changed, 1329 insertions(+), 104 deletions(-)
 create mode 100644 include/linux/kvm_dirty_ring.h
 delete mode 100644 tools/testing/selftests/kvm/clear_dirty_log_test.c
 create mode 100644 virt/kvm/dirty_ring.c

-- 
2.21.0


^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-11-29 21:32 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
@ 2019-11-29 21:32 ` Peter Xu
  0 siblings, 0 replies; 7+ messages in thread
From: Peter Xu @ 2019-11-29 21:32 UTC (permalink / raw)
  To: linux-kernel, kvm
  Cc: Paolo Bonzini, Cao Lei, peterx, Dr . David Alan Gilbert,
	Sean Christopherson, Vitaly Kuznetsov

From: Paolo Bonzini <pbonzini@redhat.com>

For ring-based dirty log tracking, it will be more efficient to account
writes during schedule-out or schedule-in to the currently running VCPU.
We would like to do it even if the write doesn't use the current VCPU's
address space, as is the case for cached writes (see commit 4e335d9e7ddb,
"Revert "KVM: Support vCPU-based gfn->hva cache"", 2017-05-02).

Therefore, add a mechanism to track the currently-loaded kvm_vcpu struct.
There is already something similar in KVM/ARM; one important difference
is that kvm_arch_vcpu_{load,put} have two callers in virt/kvm/kvm_main.c:
we have to update both the architecture-independent vcpu_{load,put} and
the preempt notifiers.

Another change made in the process is to allow using kvm_get_running_vcpu()
in preemptible code.  This is allowed because preempt notifiers ensure
that the value does not change even after the VCPU thread is migrated.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/arm/include/asm/kvm_host.h   |  2 --
 arch/arm64/include/asm/kvm_host.h |  2 --
 include/linux/kvm_host.h          |  3 +++
 virt/kvm/arm/arm.c                | 29 -----------------------------
 virt/kvm/arm/perf.c               |  6 +++---
 virt/kvm/arm/vgic/vgic-mmio.c     | 15 +++------------
 virt/kvm/kvm_main.c               | 25 ++++++++++++++++++++++++-
 7 files changed, 33 insertions(+), 49 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 556cd818eccf..abc3f6f3ad76 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -284,8 +284,6 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b36dae9ee5f9..d97855e41469 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -446,8 +446,6 @@ int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7ed1e2f8641e..498a39462ac1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1342,6 +1342,9 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
 }
 #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
 
+struct kvm_vcpu *kvm_get_running_vcpu(void);
+struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
+
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 bool kvm_arch_has_irq_bypass(void);
 int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 12e0280291ce..1df9c39024fa 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -51,9 +51,6 @@ __asm__(".arch_extension	virt");
 DEFINE_PER_CPU(kvm_host_data_t, kvm_host_data);
 static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
 
-/* Per-CPU variable containing the currently running vcpu. */
-static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_arm_running_vcpu);
-
 /* The VMID used in the VTTBR */
 static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
 static u32 kvm_next_vmid;
@@ -62,31 +59,8 @@ static DEFINE_SPINLOCK(kvm_vmid_lock);
 static bool vgic_present;
 
 static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
-
-static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
-{
-	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
-}
-
 DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
-/**
- * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU.
- * Must be called from non-preemptible context
- */
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
-{
-	return __this_cpu_read(kvm_arm_running_vcpu);
-}
-
-/**
- * kvm_arm_get_running_vcpus - get the per-CPU array of currently running vcpus.
- */
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
-{
-	return &kvm_arm_running_vcpu;
-}
-
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -406,7 +380,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	vcpu->cpu = cpu;
 	vcpu->arch.host_cpu_context = &cpu_data->host_ctxt;
 
-	kvm_arm_set_running_vcpu(vcpu);
 	kvm_vgic_load(vcpu);
 	kvm_timer_vcpu_load(vcpu);
 	kvm_vcpu_load_sysregs(vcpu);
@@ -432,8 +405,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	kvm_vcpu_pmu_restore_host(vcpu);
 
 	vcpu->cpu = -1;
-
-	kvm_arm_set_running_vcpu(NULL);
 }
 
 static void vcpu_power_off(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/perf.c b/virt/kvm/arm/perf.c
index 918cdc3839ea..d45b8b9a4415 100644
--- a/virt/kvm/arm/perf.c
+++ b/virt/kvm/arm/perf.c
@@ -13,14 +13,14 @@
 
 static int kvm_is_in_guest(void)
 {
-        return kvm_arm_get_running_vcpu() != NULL;
+        return kvm_get_running_vcpu() != NULL;
 }
 
 static int kvm_is_user_mode(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return !vcpu_mode_priv(vcpu);
@@ -32,7 +32,7 @@ static unsigned long kvm_get_guest_ip(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return *vcpu_pc(vcpu);
diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 0d090482720d..d656ebd5f9d4 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -190,15 +190,6 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
  * 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;
-}
 
 /* Must be called with irq->irq_lock held */
 static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
@@ -221,7 +212,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -274,7 +265,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -335,7 +326,7 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 				    bool active)
 {
 	unsigned long flags;
-	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
+	struct kvm_vcpu *requester_vcpu = kvm_get_running_vcpu();
 
 	raw_spin_lock_irqsave(&irq->irq_lock, flags);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 00268290dcbd..fac0760c870e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -108,6 +108,7 @@ struct kmem_cache *kvm_vcpu_cache;
 EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
 
 static __read_mostly struct preempt_ops kvm_preempt_ops;
+static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);
 
 struct dentry *kvm_debugfs_dir;
 EXPORT_SYMBOL_GPL(kvm_debugfs_dir);
@@ -197,6 +198,8 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
 void vcpu_load(struct kvm_vcpu *vcpu)
 {
 	int cpu = get_cpu();
+
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	preempt_notifier_register(&vcpu->preempt_notifier);
 	kvm_arch_vcpu_load(vcpu, cpu);
 	put_cpu();
@@ -208,6 +211,7 @@ void vcpu_put(struct kvm_vcpu *vcpu)
 	preempt_disable();
 	kvm_arch_vcpu_put(vcpu);
 	preempt_notifier_unregister(&vcpu->preempt_notifier);
+	__this_cpu_write(kvm_running_vcpu, NULL);
 	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(vcpu_put);
@@ -4304,8 +4308,8 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
 	WRITE_ONCE(vcpu->preempted, false);
 	WRITE_ONCE(vcpu->ready, false);
 
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	kvm_arch_sched_in(vcpu, cpu);
-
 	kvm_arch_vcpu_load(vcpu, cpu);
 }
 
@@ -4319,6 +4323,25 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 		WRITE_ONCE(vcpu->ready, true);
 	}
 	kvm_arch_vcpu_put(vcpu);
+	__this_cpu_write(kvm_running_vcpu, NULL);
+}
+
+/**
+ * kvm_get_running_vcpu - get the vcpu running on the current CPU.
+ * Thanks to preempt notifiers, this can also be called from
+ * preemptible context.
+ */
+struct kvm_vcpu *kvm_get_running_vcpu(void)
+{
+        return __this_cpu_read(kvm_running_vcpu);
+}
+
+/**
+ * kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
+ */
+struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
+{
+        return &kvm_running_vcpu;
 }
 
 static void check_processor_compat(void *rtn)
-- 
2.21.0


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-12-04  9:42     ` Paolo Bonzini
@ 2019-12-09 22:05       ` Peter Xu
  0 siblings, 0 replies; 7+ messages in thread
From: Peter Xu @ 2019-12-09 22:05 UTC (permalink / raw)
  To: Paolo Bonzini
  Cc: Sean Christopherson, linux-kernel, kvm, Dr . David Alan Gilbert,
	Vitaly Kuznetsov

On Wed, Dec 04, 2019 at 10:42:27AM +0100, Paolo Bonzini wrote:
> On 03/12/19 20:01, Sean Christopherson wrote:
> > In case it was clear, I strongly dislike adding kvm_get_running_vcpu().
> > IMO, it's a unnecessary hack.  The proper change to ensure a valid vCPU is
> > seen by mark_page_dirty_in_ring() when there is a current vCPU is to
> > plumb the vCPU down through the various call stacks.  Looking up the call
> > stacks for mark_page_dirty() and mark_page_dirty_in_slot(), they all
> > originate with a vcpu->kvm within a few functions, except for the rare
> > case where the write is coming from a non-vcpu ioctl(), in which case
> > there is no current vCPU.
> > 
> > The proper change is obviously much bigger in scope and would require
> > touching gobs of arch specific code, but IMO the end result would be worth
> > the effort.  E.g. there's a decent chance it would reduce the API between
> > common KVM and arch specific code by eliminating the exports of variants
> > that take "struct kvm *" instead of "struct kvm_vcpu *".
> 
> It's not that simple.  In some cases, the "struct kvm *" cannot be
> easily replaced with a "struct kvm_vcpu *" without making the API less
> intuitive; for example think of a function that takes a kvm_vcpu pointer
> but then calls gfn_to_hva(vcpu->kvm) instead of the expected
> kvm_vcpu_gfn_to_hva(vcpu).
> 
> That said, looking at the code again after a couple years I agree that
> the usage of kvm_get_running_vcpu() is ugly.  But I don't think it's
> kvm_get_running_vcpu()'s fault, rather it's the vCPU argument in
> mark_page_dirty_in_slot and mark_page_dirty_in_ring that is confusing
> and we should not be adding.
> 
> kvm_get_running_vcpu() basically means "you can use the per-vCPU ring
> and avoid locking", nothing more.  Right now we need the vCPU argument
> in mark_page_dirty_in_ring for kvm_arch_vcpu_memslots_id(vcpu), but that
> is unnecessary and is the real source of confusion (possibly bugs too)
> if it gets out of sync.
> 
> Instead, let's add an as_id field to struct kvm_memory_slot (which is
> trivial to initialize in __kvm_set_memory_region), and just do
> 
> 	as_id = slot->as_id;
> 	vcpu = kvm_get_running_vcpu();
> 
> in mark_page_dirty_in_ring.

Looks good.  I'm adding another patch for it, and dropping patch 2 then.

Thanks,

-- 
Peter Xu


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-12-03 19:01   ` Sean Christopherson
@ 2019-12-04  9:42     ` Paolo Bonzini
  2019-12-09 22:05       ` Peter Xu
  0 siblings, 1 reply; 7+ messages in thread
From: Paolo Bonzini @ 2019-12-04  9:42 UTC (permalink / raw)
  To: Sean Christopherson, Peter Xu
  Cc: linux-kernel, kvm, Dr . David Alan Gilbert, Vitaly Kuznetsov

On 03/12/19 20:01, Sean Christopherson wrote:
> In case it was clear, I strongly dislike adding kvm_get_running_vcpu().
> IMO, it's a unnecessary hack.  The proper change to ensure a valid vCPU is
> seen by mark_page_dirty_in_ring() when there is a current vCPU is to
> plumb the vCPU down through the various call stacks.  Looking up the call
> stacks for mark_page_dirty() and mark_page_dirty_in_slot(), they all
> originate with a vcpu->kvm within a few functions, except for the rare
> case where the write is coming from a non-vcpu ioctl(), in which case
> there is no current vCPU.
> 
> The proper change is obviously much bigger in scope and would require
> touching gobs of arch specific code, but IMO the end result would be worth
> the effort.  E.g. there's a decent chance it would reduce the API between
> common KVM and arch specific code by eliminating the exports of variants
> that take "struct kvm *" instead of "struct kvm_vcpu *".

It's not that simple.  In some cases, the "struct kvm *" cannot be
easily replaced with a "struct kvm_vcpu *" without making the API less
intuitive; for example think of a function that takes a kvm_vcpu pointer
but then calls gfn_to_hva(vcpu->kvm) instead of the expected
kvm_vcpu_gfn_to_hva(vcpu).

That said, looking at the code again after a couple years I agree that
the usage of kvm_get_running_vcpu() is ugly.  But I don't think it's
kvm_get_running_vcpu()'s fault, rather it's the vCPU argument in
mark_page_dirty_in_slot and mark_page_dirty_in_ring that is confusing
and we should not be adding.

kvm_get_running_vcpu() basically means "you can use the per-vCPU ring
and avoid locking", nothing more.  Right now we need the vCPU argument
in mark_page_dirty_in_ring for kvm_arch_vcpu_memslots_id(vcpu), but that
is unnecessary and is the real source of confusion (possibly bugs too)
if it gets out of sync.

Instead, let's add an as_id field to struct kvm_memory_slot (which is
trivial to initialize in __kvm_set_memory_region), and just do

	as_id = slot->as_id;
	vcpu = kvm_get_running_vcpu();

in mark_page_dirty_in_ring.

Paolo


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-11-29 21:34 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
@ 2019-12-03 19:01   ` Sean Christopherson
  2019-12-04  9:42     ` Paolo Bonzini
  0 siblings, 1 reply; 7+ messages in thread
From: Sean Christopherson @ 2019-12-03 19:01 UTC (permalink / raw)
  To: Peter Xu
  Cc: linux-kernel, kvm, Paolo Bonzini, Dr . David Alan Gilbert,
	Vitaly Kuznetsov

On Fri, Nov 29, 2019 at 04:34:51PM -0500, Peter Xu wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> For ring-based dirty log tracking, it will be more efficient to account
> writes during schedule-out or schedule-in to the currently running VCPU.
> We would like to do it even if the write doesn't use the current VCPU's
> address space, as is the case for cached writes (see commit 4e335d9e7ddb,
> "Revert "KVM: Support vCPU-based gfn->hva cache"", 2017-05-02).
> 
> Therefore, add a mechanism to track the currently-loaded kvm_vcpu struct.
> There is already something similar in KVM/ARM; one important difference
> is that kvm_arch_vcpu_{load,put} have two callers in virt/kvm/kvm_main.c:
> we have to update both the architecture-independent vcpu_{load,put} and
> the preempt notifiers.
> 
> Another change made in the process is to allow using kvm_get_running_vcpu()
> in preemptible code.  This is allowed because preempt notifiers ensure
> that the value does not change even after the VCPU thread is migrated.

In case it was clear, I strongly dislike adding kvm_get_running_vcpu().
IMO, it's a unnecessary hack.  The proper change to ensure a valid vCPU is
seen by mark_page_dirty_in_ring() when there is a current vCPU is to
plumb the vCPU down through the various call stacks.  Looking up the call
stacks for mark_page_dirty() and mark_page_dirty_in_slot(), they all
originate with a vcpu->kvm within a few functions, except for the rare
case where the write is coming from a non-vcpu ioctl(), in which case
there is no current vCPU.

The proper change is obviously much bigger in scope and would require
touching gobs of arch specific code, but IMO the end result would be worth
the effort.  E.g. there's a decent chance it would reduce the API between
common KVM and arch specific code by eliminating the exports of variants
that take "struct kvm *" instead of "struct kvm_vcpu *".

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-11-29 21:34 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
@ 2019-11-29 21:34 ` Peter Xu
  2019-12-03 19:01   ` Sean Christopherson
  0 siblings, 1 reply; 7+ messages in thread
From: Peter Xu @ 2019-11-29 21:34 UTC (permalink / raw)
  To: linux-kernel, kvm
  Cc: Sean Christopherson, Paolo Bonzini, Dr . David Alan Gilbert,
	peterx, Vitaly Kuznetsov

From: Paolo Bonzini <pbonzini@redhat.com>

For ring-based dirty log tracking, it will be more efficient to account
writes during schedule-out or schedule-in to the currently running VCPU.
We would like to do it even if the write doesn't use the current VCPU's
address space, as is the case for cached writes (see commit 4e335d9e7ddb,
"Revert "KVM: Support vCPU-based gfn->hva cache"", 2017-05-02).

Therefore, add a mechanism to track the currently-loaded kvm_vcpu struct.
There is already something similar in KVM/ARM; one important difference
is that kvm_arch_vcpu_{load,put} have two callers in virt/kvm/kvm_main.c:
we have to update both the architecture-independent vcpu_{load,put} and
the preempt notifiers.

Another change made in the process is to allow using kvm_get_running_vcpu()
in preemptible code.  This is allowed because preempt notifiers ensure
that the value does not change even after the VCPU thread is migrated.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/arm/include/asm/kvm_host.h   |  2 --
 arch/arm64/include/asm/kvm_host.h |  2 --
 include/linux/kvm_host.h          |  3 +++
 virt/kvm/arm/arm.c                | 29 -----------------------------
 virt/kvm/arm/perf.c               |  6 +++---
 virt/kvm/arm/vgic/vgic-mmio.c     | 15 +++------------
 virt/kvm/kvm_main.c               | 25 ++++++++++++++++++++++++-
 7 files changed, 33 insertions(+), 49 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 556cd818eccf..abc3f6f3ad76 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -284,8 +284,6 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b36dae9ee5f9..d97855e41469 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -446,8 +446,6 @@ int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7ed1e2f8641e..498a39462ac1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1342,6 +1342,9 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
 }
 #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
 
+struct kvm_vcpu *kvm_get_running_vcpu(void);
+struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
+
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 bool kvm_arch_has_irq_bypass(void);
 int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 12e0280291ce..1df9c39024fa 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -51,9 +51,6 @@ __asm__(".arch_extension	virt");
 DEFINE_PER_CPU(kvm_host_data_t, kvm_host_data);
 static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
 
-/* Per-CPU variable containing the currently running vcpu. */
-static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_arm_running_vcpu);
-
 /* The VMID used in the VTTBR */
 static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
 static u32 kvm_next_vmid;
@@ -62,31 +59,8 @@ static DEFINE_SPINLOCK(kvm_vmid_lock);
 static bool vgic_present;
 
 static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
-
-static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
-{
-	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
-}
-
 DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
-/**
- * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU.
- * Must be called from non-preemptible context
- */
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
-{
-	return __this_cpu_read(kvm_arm_running_vcpu);
-}
-
-/**
- * kvm_arm_get_running_vcpus - get the per-CPU array of currently running vcpus.
- */
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
-{
-	return &kvm_arm_running_vcpu;
-}
-
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -406,7 +380,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	vcpu->cpu = cpu;
 	vcpu->arch.host_cpu_context = &cpu_data->host_ctxt;
 
-	kvm_arm_set_running_vcpu(vcpu);
 	kvm_vgic_load(vcpu);
 	kvm_timer_vcpu_load(vcpu);
 	kvm_vcpu_load_sysregs(vcpu);
@@ -432,8 +405,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	kvm_vcpu_pmu_restore_host(vcpu);
 
 	vcpu->cpu = -1;
-
-	kvm_arm_set_running_vcpu(NULL);
 }
 
 static void vcpu_power_off(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/perf.c b/virt/kvm/arm/perf.c
index 918cdc3839ea..d45b8b9a4415 100644
--- a/virt/kvm/arm/perf.c
+++ b/virt/kvm/arm/perf.c
@@ -13,14 +13,14 @@
 
 static int kvm_is_in_guest(void)
 {
-        return kvm_arm_get_running_vcpu() != NULL;
+        return kvm_get_running_vcpu() != NULL;
 }
 
 static int kvm_is_user_mode(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return !vcpu_mode_priv(vcpu);
@@ -32,7 +32,7 @@ static unsigned long kvm_get_guest_ip(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return *vcpu_pc(vcpu);
diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 0d090482720d..d656ebd5f9d4 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -190,15 +190,6 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
  * 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;
-}
 
 /* Must be called with irq->irq_lock held */
 static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
@@ -221,7 +212,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -274,7 +265,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -335,7 +326,7 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 				    bool active)
 {
 	unsigned long flags;
-	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
+	struct kvm_vcpu *requester_vcpu = kvm_get_running_vcpu();
 
 	raw_spin_lock_irqsave(&irq->irq_lock, flags);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 00268290dcbd..fac0760c870e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -108,6 +108,7 @@ struct kmem_cache *kvm_vcpu_cache;
 EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
 
 static __read_mostly struct preempt_ops kvm_preempt_ops;
+static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);
 
 struct dentry *kvm_debugfs_dir;
 EXPORT_SYMBOL_GPL(kvm_debugfs_dir);
@@ -197,6 +198,8 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
 void vcpu_load(struct kvm_vcpu *vcpu)
 {
 	int cpu = get_cpu();
+
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	preempt_notifier_register(&vcpu->preempt_notifier);
 	kvm_arch_vcpu_load(vcpu, cpu);
 	put_cpu();
@@ -208,6 +211,7 @@ void vcpu_put(struct kvm_vcpu *vcpu)
 	preempt_disable();
 	kvm_arch_vcpu_put(vcpu);
 	preempt_notifier_unregister(&vcpu->preempt_notifier);
+	__this_cpu_write(kvm_running_vcpu, NULL);
 	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(vcpu_put);
@@ -4304,8 +4308,8 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
 	WRITE_ONCE(vcpu->preempted, false);
 	WRITE_ONCE(vcpu->ready, false);
 
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	kvm_arch_sched_in(vcpu, cpu);
-
 	kvm_arch_vcpu_load(vcpu, cpu);
 }
 
@@ -4319,6 +4323,25 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 		WRITE_ONCE(vcpu->ready, true);
 	}
 	kvm_arch_vcpu_put(vcpu);
+	__this_cpu_write(kvm_running_vcpu, NULL);
+}
+
+/**
+ * kvm_get_running_vcpu - get the vcpu running on the current CPU.
+ * Thanks to preempt notifiers, this can also be called from
+ * preemptible context.
+ */
+struct kvm_vcpu *kvm_get_running_vcpu(void)
+{
+        return __this_cpu_read(kvm_running_vcpu);
+}
+
+/**
+ * kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
+ */
+struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
+{
+        return &kvm_running_vcpu;
 }
 
 static void check_processor_compat(void *rtn)
-- 
2.21.0


^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code
  2019-11-29 21:33 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
@ 2019-11-29 21:33 ` Peter Xu
  0 siblings, 0 replies; 7+ messages in thread
From: Peter Xu @ 2019-11-29 21:33 UTC (permalink / raw)
  To: linux-kernel, kvm
  Cc: Sean Christopherson, Paolo Bonzini, Dr . David Alan Gilbert,
	peterx, Vitaly Kuznetsov

From: Paolo Bonzini <pbonzini@redhat.com>

For ring-based dirty log tracking, it will be more efficient to account
writes during schedule-out or schedule-in to the currently running VCPU.
We would like to do it even if the write doesn't use the current VCPU's
address space, as is the case for cached writes (see commit 4e335d9e7ddb,
"Revert "KVM: Support vCPU-based gfn->hva cache"", 2017-05-02).

Therefore, add a mechanism to track the currently-loaded kvm_vcpu struct.
There is already something similar in KVM/ARM; one important difference
is that kvm_arch_vcpu_{load,put} have two callers in virt/kvm/kvm_main.c:
we have to update both the architecture-independent vcpu_{load,put} and
the preempt notifiers.

Another change made in the process is to allow using kvm_get_running_vcpu()
in preemptible code.  This is allowed because preempt notifiers ensure
that the value does not change even after the VCPU thread is migrated.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 arch/arm/include/asm/kvm_host.h   |  2 --
 arch/arm64/include/asm/kvm_host.h |  2 --
 include/linux/kvm_host.h          |  3 +++
 virt/kvm/arm/arm.c                | 29 -----------------------------
 virt/kvm/arm/perf.c               |  6 +++---
 virt/kvm/arm/vgic/vgic-mmio.c     | 15 +++------------
 virt/kvm/kvm_main.c               | 25 ++++++++++++++++++++++++-
 7 files changed, 33 insertions(+), 49 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 556cd818eccf..abc3f6f3ad76 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -284,8 +284,6 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b36dae9ee5f9..d97855e41469 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -446,8 +446,6 @@ int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
 int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
 int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7ed1e2f8641e..498a39462ac1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1342,6 +1342,9 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
 }
 #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
 
+struct kvm_vcpu *kvm_get_running_vcpu(void);
+struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
+
 #ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
 bool kvm_arch_has_irq_bypass(void);
 int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 12e0280291ce..1df9c39024fa 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -51,9 +51,6 @@ __asm__(".arch_extension	virt");
 DEFINE_PER_CPU(kvm_host_data_t, kvm_host_data);
 static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
 
-/* Per-CPU variable containing the currently running vcpu. */
-static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_arm_running_vcpu);
-
 /* The VMID used in the VTTBR */
 static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
 static u32 kvm_next_vmid;
@@ -62,31 +59,8 @@ static DEFINE_SPINLOCK(kvm_vmid_lock);
 static bool vgic_present;
 
 static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
-
-static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
-{
-	__this_cpu_write(kvm_arm_running_vcpu, vcpu);
-}
-
 DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
-/**
- * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU.
- * Must be called from non-preemptible context
- */
-struct kvm_vcpu *kvm_arm_get_running_vcpu(void)
-{
-	return __this_cpu_read(kvm_arm_running_vcpu);
-}
-
-/**
- * kvm_arm_get_running_vcpus - get the per-CPU array of currently running vcpus.
- */
-struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
-{
-	return &kvm_arm_running_vcpu;
-}
-
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -406,7 +380,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	vcpu->cpu = cpu;
 	vcpu->arch.host_cpu_context = &cpu_data->host_ctxt;
 
-	kvm_arm_set_running_vcpu(vcpu);
 	kvm_vgic_load(vcpu);
 	kvm_timer_vcpu_load(vcpu);
 	kvm_vcpu_load_sysregs(vcpu);
@@ -432,8 +405,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	kvm_vcpu_pmu_restore_host(vcpu);
 
 	vcpu->cpu = -1;
-
-	kvm_arm_set_running_vcpu(NULL);
 }
 
 static void vcpu_power_off(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/perf.c b/virt/kvm/arm/perf.c
index 918cdc3839ea..d45b8b9a4415 100644
--- a/virt/kvm/arm/perf.c
+++ b/virt/kvm/arm/perf.c
@@ -13,14 +13,14 @@
 
 static int kvm_is_in_guest(void)
 {
-        return kvm_arm_get_running_vcpu() != NULL;
+        return kvm_get_running_vcpu() != NULL;
 }
 
 static int kvm_is_user_mode(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return !vcpu_mode_priv(vcpu);
@@ -32,7 +32,7 @@ static unsigned long kvm_get_guest_ip(void)
 {
 	struct kvm_vcpu *vcpu;
 
-	vcpu = kvm_arm_get_running_vcpu();
+	vcpu = kvm_get_running_vcpu();
 
 	if (vcpu)
 		return *vcpu_pc(vcpu);
diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
index 0d090482720d..d656ebd5f9d4 100644
--- a/virt/kvm/arm/vgic/vgic-mmio.c
+++ b/virt/kvm/arm/vgic/vgic-mmio.c
@@ -190,15 +190,6 @@ unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
  * 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;
-}
 
 /* Must be called with irq->irq_lock held */
 static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
@@ -221,7 +212,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -274,7 +265,7 @@ 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();
+	bool is_uaccess = !kvm_get_running_vcpu();
 	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
 	int i;
 	unsigned long flags;
@@ -335,7 +326,7 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
 				    bool active)
 {
 	unsigned long flags;
-	struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();
+	struct kvm_vcpu *requester_vcpu = kvm_get_running_vcpu();
 
 	raw_spin_lock_irqsave(&irq->irq_lock, flags);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 00268290dcbd..fac0760c870e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -108,6 +108,7 @@ struct kmem_cache *kvm_vcpu_cache;
 EXPORT_SYMBOL_GPL(kvm_vcpu_cache);
 
 static __read_mostly struct preempt_ops kvm_preempt_ops;
+static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);
 
 struct dentry *kvm_debugfs_dir;
 EXPORT_SYMBOL_GPL(kvm_debugfs_dir);
@@ -197,6 +198,8 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
 void vcpu_load(struct kvm_vcpu *vcpu)
 {
 	int cpu = get_cpu();
+
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	preempt_notifier_register(&vcpu->preempt_notifier);
 	kvm_arch_vcpu_load(vcpu, cpu);
 	put_cpu();
@@ -208,6 +211,7 @@ void vcpu_put(struct kvm_vcpu *vcpu)
 	preempt_disable();
 	kvm_arch_vcpu_put(vcpu);
 	preempt_notifier_unregister(&vcpu->preempt_notifier);
+	__this_cpu_write(kvm_running_vcpu, NULL);
 	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(vcpu_put);
@@ -4304,8 +4308,8 @@ static void kvm_sched_in(struct preempt_notifier *pn, int cpu)
 	WRITE_ONCE(vcpu->preempted, false);
 	WRITE_ONCE(vcpu->ready, false);
 
+	__this_cpu_write(kvm_running_vcpu, vcpu);
 	kvm_arch_sched_in(vcpu, cpu);
-
 	kvm_arch_vcpu_load(vcpu, cpu);
 }
 
@@ -4319,6 +4323,25 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 		WRITE_ONCE(vcpu->ready, true);
 	}
 	kvm_arch_vcpu_put(vcpu);
+	__this_cpu_write(kvm_running_vcpu, NULL);
+}
+
+/**
+ * kvm_get_running_vcpu - get the vcpu running on the current CPU.
+ * Thanks to preempt notifiers, this can also be called from
+ * preemptible context.
+ */
+struct kvm_vcpu *kvm_get_running_vcpu(void)
+{
+        return __this_cpu_read(kvm_running_vcpu);
+}
+
+/**
+ * kvm_get_running_vcpus - get the per-CPU array of currently running vcpus.
+ */
+struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
+{
+        return &kvm_running_vcpu;
 }
 
 static void check_processor_compat(void *rtn)
-- 
2.21.0


^ permalink raw reply	[flat|nested] 7+ messages in thread

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Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-29 21:32 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
2019-11-29 21:32 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
2019-11-29 21:33 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
2019-11-29 21:33 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
2019-11-29 21:34 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
2019-11-29 21:34 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
2019-12-03 19:01   ` Sean Christopherson
2019-12-04  9:42     ` Paolo Bonzini
2019-12-09 22:05       ` Peter Xu

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