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From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Cc: roy.hopkins@suse.com,
seanjc@google.com,
thomas.lendacky@amd.com,
ashish.kalra@amd.com,
michael.roth@amd.com,
jroedel@suse.de,
nsaenz@amazon.com,
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James.Bottomley@HansenPartnership.com
Subject: [PATCH 12/29] KVM: share dirty ring for same vCPU id on different
planes
Date: Tue, 1 Apr 2025 18:10:49 +0200
Message-ID: <20250401161106.790710-13-pbonzini@redhat.com>
X-Mailer: git-send-email 2.49.0
In-Reply-To: <20250401161106.790710-1-pbonzini@redhat.com>
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The dirty page ring is read by mmap()-ing the vCPU file descriptor,
which is only possible for plane 0. This is not a problem because it
is only filled by KVM_RUN which takes the plane-0 vCPU mutex, and it is
therefore possible to share it for vCPUs that have the same id but are
on different planes. (TODO: double check).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
include/linux/kvm_host.h | 6 ++++--
virt/kvm/dirty_ring.c | 5 +++--
virt/kvm/kvm_main.c | 10 +++++-----
3 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d2e0c0e8ff17..b511aed2de8e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -394,9 +394,11 @@ struct kvm_vcpu {
bool scheduled_out;
struct kvm_vcpu_arch arch;
struct kvm_vcpu_stat *stat;
- struct kvm_vcpu_stat __stat;
char stats_id[KVM_STATS_NAME_SIZE];
- struct kvm_dirty_ring dirty_ring;
+ struct kvm_dirty_ring *dirty_ring;
+
+ struct kvm_vcpu_stat __stat;
+ struct kvm_dirty_ring __dirty_ring;
=20
/*
* The most recently used memslot by this vCPU and the slots generation
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index d14ffc7513ee..66e6a6a67d13 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -172,11 +172,12 @@ int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_=
dirty_ring *ring)
=20
void kvm_dirty_ring_push(struct kvm_vcpu *vcpu, u32 slot, u64 offset)
{
- struct kvm_dirty_ring *ring =3D &vcpu->dirty_ring;
+ struct kvm_dirty_ring *ring =3D vcpu->dirty_ring;
struct kvm_dirty_gfn *entry;
=20
/* It should never get full */
WARN_ON_ONCE(kvm_dirty_ring_full(ring));
+ lockdep_assert_held(&vcpu->plane0->mutex);
=20
entry =3D &ring->dirty_gfns[ring->dirty_index & (ring->size - 1)];
=20
@@ -204,7 +205,7 @@ bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu)
* the dirty ring is reset by userspace.
*/
if (kvm_check_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu) &&
- kvm_dirty_ring_soft_full(&vcpu->dirty_ring)) {
+ kvm_dirty_ring_soft_full(vcpu->dirty_ring)) {
kvm_make_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
vcpu->run->exit_reason =3D KVM_EXIT_DIRTY_RING_FULL;
trace_kvm_dirty_ring_exit(vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4c7e379fbf7d..863fd80ddfbe 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -466,7 +466,7 @@ static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct=
kvm *kvm, unsigned id)
static void kvm_vcpu_destroy(struct kvm_vcpu *vcpu)
{
kvm_arch_vcpu_destroy(vcpu);
- kvm_dirty_ring_free(&vcpu->dirty_ring);
+ kvm_dirty_ring_free(vcpu->dirty_ring);
=20
/*
* No need for rcu_read_lock as VCPU_RUN is the only place that changes
@@ -4038,7 +4038,7 @@ static vm_fault_t kvm_vcpu_fault(struct vm_fault *vmf)
#endif
else if (kvm_page_in_dirty_ring(vcpu->kvm, vmf->pgoff))
page =3D kvm_dirty_ring_get_page(
- &vcpu->dirty_ring,
+ vcpu->dirty_ring,
vmf->pgoff - KVM_DIRTY_LOG_PAGE_OFFSET);
else
return kvm_arch_vcpu_fault(vcpu, vmf);
@@ -4174,7 +4174,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, =
unsigned long id)
vcpu->run =3D page_address(page);
=20
if (kvm->dirty_ring_size) {
- r =3D kvm_dirty_ring_alloc(kvm, &vcpu->dirty_ring,
+ r =3D kvm_dirty_ring_alloc(kvm, &vcpu->__dirty_ring,
id, kvm->dirty_ring_size);
if (r)
goto vcpu_free_run_page;
@@ -4242,7 +4242,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, =
unsigned long id)
mutex_unlock(&kvm->lock);
kvm_arch_vcpu_destroy(vcpu);
vcpu_free_dirty_ring:
- kvm_dirty_ring_free(&vcpu->dirty_ring);
+ kvm_dirty_ring_free(&vcpu->__dirty_ring);
vcpu_free_run_page:
free_page((unsigned long)vcpu->run);
vcpu_free:
@@ -5047,7 +5047,7 @@ static int kvm_vm_ioctl_reset_dirty_pages(struct kvm =
*kvm)
mutex_lock(&kvm->slots_lock);
=20
kvm_for_each_vcpu(i, vcpu, kvm)
- cleared +=3D kvm_dirty_ring_reset(vcpu->kvm, &vcpu->dirty_ring);
+ cleared +=3D kvm_dirty_ring_reset(vcpu->kvm, vcpu->dirty_ring);
=20
mutex_unlock(&kvm->slots_lock);
=20
--=20
2.49.0