From: Sean Christopherson <seanjc@xxxxxxxxxx>
Handle the "no memslot" case at the beginning of kvm_faultin_pfn(), just
after the private versus shared check, so that there's no need to
repeatedly query whether or not a slot exists. This also makes it more
obvious that, except for private vs. shared attributes, the process of
faulting in a pfn simply doesn't apply to gfns without a slot.
Opportunistically stuff @fault's metadata in kvm_handle_noslot_fault() so
that it doesn't need to be duplicated in all paths that invoke
kvm_handle_noslot_fault(), and to minimize the probability of not stuffing
the right fields.
Leave the existing handle behind, but convert it to a WARN, to guard
against __kvm_faultin_pfn() unexpectedly nullifying fault->slot.
Cc: David Matlack <dmatlack@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
Message-ID: <20240228024147.41573-14-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b09c8034ed15..7630ad8cb022 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3270,6 +3270,10 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
access & shadow_mmio_access_mask);
+ fault->slot = NULL;
+ fault->pfn = KVM_PFN_NOSLOT;
+ fault->map_writable = false;
+
/*
* If MMIO caching is disabled, emulate immediately without
* touching the shadow page tables as attempting to install an
@@ -4350,15 +4354,18 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
return -EFAULT;
}
+ if (unlikely(!slot))
+ return kvm_handle_noslot_fault(vcpu, fault, access);
+
/*
* Retry the page fault if the gfn hit a memslot that is being deleted
* or moved. This ensures any existing SPTEs for the old memslot will
* be zapped before KVM inserts a new MMIO SPTE for the gfn.
*/
- if (slot && (slot->flags & KVM_MEMSLOT_INVALID))
+ if (slot->flags & KVM_MEMSLOT_INVALID)
return RET_PF_RETRY;
- if (slot && slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT) {
+ if (slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT) {
/*
* Don't map L1's APIC access page into L2, KVM doesn't support
* using APICv/AVIC to accelerate L2 accesses to L1's APIC,
@@ -4370,12 +4377,9 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
* uses different roots for L1 vs. L2, i.e. there is no danger
* of breaking APICv/AVIC for L1.
*/
- if (is_guest_mode(vcpu)) {
- fault->slot = NULL;
- fault->pfn = KVM_PFN_NOSLOT;
- fault->map_writable = false;
- goto faultin_done;
- }
+ if (is_guest_mode(vcpu))
+ return kvm_handle_noslot_fault(vcpu, fault, access);
+
/*
* If the APIC access page exists but is disabled, go directly
* to emulation without caching the MMIO access or creating a
@@ -4386,6 +4390,9 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
return RET_PF_EMULATE;
}
+ fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
+ smp_rmb();
+
/*
* Check for a relevant mmu_notifier invalidation event before getting
* the pfn from the primary MMU, and before acquiring mmu_lock.
@@ -4407,19 +4414,17 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
* *guaranteed* to need to retry, i.e. waiting until mmu_lock is held
* to detect retry guarantees the worst case latency for the vCPU.
*/
- if (fault->slot &&
- mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn))
+ if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn))
return RET_PF_RETRY;
ret = __kvm_faultin_pfn(vcpu, fault);
if (ret != RET_PF_CONTINUE)
return ret;
-faultin_done:
if (unlikely(is_error_pfn(fault->pfn)))
return kvm_handle_error_pfn(vcpu, fault);
- if (unlikely(!fault->slot))
+ if (WARN_ON_ONCE(!fault->slot))
return kvm_handle_noslot_fault(vcpu, fault, access);
/*
--
2.43.0
