From: Sean Christopherson <[email protected]> Explicitly mark the Xen shared info page as never being dirty tracked so that higher-level gpc APIs can be added to automatically take care of things like dirty tracking, without reintroducing the bug fixed by commit 55749769fe60 ("KVM: x86: Fix wall clock writes in Xen shared_info not to mark page dirty"). And because the code _looks_ buggy.
No functional change intended. Signed-off-by: Sean Christopherson <[email protected]> Signed-off-by: David Woodhouse <[email protected]> Assisted-by: Claude:claude-mythos-5 --- arch/x86/kvm/xen.c | 2 +- include/linux/kvm_host.h | 10 ++++++++-- include/linux/kvm_types.h | 1 + virt/kvm/pfncache.c | 4 +++- 4 files changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 1364fe8ee751..198d7babf964 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -2410,7 +2410,7 @@ void kvm_xen_init_vm(struct kvm *kvm) { mutex_init(&kvm->arch.xen.xen_lock); xa_init(&kvm->arch.xen.evtchn_ports); - kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm); + __kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm, true); } void kvm_xen_destroy_vm(struct kvm *kvm) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 9da947eb08ed..7b2dbbd6b104 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1474,7 +1474,13 @@ int kvm_vcpu_write_guest(struct kvm_vcpu *vcpu, gpa_t gpa, const void *data, * immutable attributes. Note, the cache must be zero-allocated (or zeroed by * the caller before init). */ -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm); +void __kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, + bool never_dirty); + +static inline void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) +{ + __kvm_gpc_init(gpc, kvm, false); +} /** * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest @@ -1983,7 +1989,7 @@ static inline void kvm_gpc_mark_dirty_in_slot(struct gfn_to_pfn_cache *gpc) RCU_LOCKDEP_WARN(!srcu_read_lock_held(&gpc->kvm->gpc_srcu), "kvm_gpc_mark_dirty_in_slot() without kvm->gpc_srcu read lock"); - if (!gpc->memslot) + if (!gpc->memslot || gpc->never_dirty) return; mark_page_dirty_in_slot(gpc->kvm, gpc->memslot, gpa_to_gfn(gpc->gpa)); diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h index 31f3eb0dd2aa..22393f97266a 100644 --- a/include/linux/kvm_types.h +++ b/include/linux/kvm_types.h @@ -109,6 +109,7 @@ struct gfn_to_pfn_cache { * instead. */ atomic_t state; + bool never_dirty; }; /* The cache is valid: pfn and khva may be used by readers. */ diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index 067da05a87ac..2fe50dfa3fc1 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -598,7 +598,8 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len) return __kvm_gpc_refresh(gpc, gpc->gpa, uhva); } -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) +void __kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, + bool never_dirty) { mutex_init(&gpc->refresh_lock); @@ -608,6 +609,7 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) gpc->uhva = KVM_HVA_ERR_BAD; gpc->active = false; atomic_set(&gpc->state, 0); + gpc->never_dirty = never_dirty; } static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva, -- 2.55.0
