Re: [PATCH 04/16] KVM: x86/mmu: Pass full 64-bit error code when handling page faults

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On 2/28/2024 10:41 AM, Sean Christopherson wrote:
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Plumb the full 64-bit error code throughout the page fault handling code
so that KVM can use the upper 32 bits, e.g. SNP's PFERR_GUEST_ENC_MASK
will be used to determine whether or not a fault is private vs. shared.

Note, passing the 64-bit error code to FNAME(walk_addr)() does NOT change
the behavior of permission_fault() when invoked in the page fault path, as
KVM explicitly clears PFERR_IMPLICIT_ACCESS in kvm_mmu_page_fault().

Continue passing '0' from the async #PF worker, as guest_memfd() and thus
private memory doesn't support async page faults.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
[mdr: drop references/changes on rebase, update commit message]
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
[sean: drop truncation in call to FNAME(walk_addr)(), rewrite changelog]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>


---
  arch/x86/kvm/mmu/mmu.c          | 3 +--
  arch/x86/kvm/mmu/mmu_internal.h | 4 ++--
  arch/x86/kvm/mmu/mmutrace.h     | 2 +-
  3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e2fd74e06ff8..408969ac1291 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5860,8 +5860,7 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
  	}
if (r == RET_PF_INVALID) {
-		r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa,
-					  lower_32_bits(error_code), false,
+		r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false,
  					  &emulation_type);
  		if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
  			return -EIO;
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 0eea6c5a824d..1fab1f2359b5 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -190,7 +190,7 @@ static inline bool is_nx_huge_page_enabled(struct kvm *kvm)
  struct kvm_page_fault {
  	/* arguments to kvm_mmu_do_page_fault.  */
  	const gpa_t addr;
-	const u32 error_code;
+	const u64 error_code;
  	const bool prefetch;
/* Derived from error_code. */
@@ -288,7 +288,7 @@ static inline void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
  }
static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
-					u32 err, bool prefetch, int *emulation_type)
+					u64 err, bool prefetch, int *emulation_type)
  {
  	struct kvm_page_fault fault = {
  		.addr = cr2_or_gpa,
diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h
index ae86820cef69..195d98bc8de8 100644
--- a/arch/x86/kvm/mmu/mmutrace.h
+++ b/arch/x86/kvm/mmu/mmutrace.h
@@ -260,7 +260,7 @@ TRACE_EVENT(
  	TP_STRUCT__entry(
  		__field(int, vcpu_id)
  		__field(gpa_t, cr2_or_gpa)
-		__field(u32, error_code)
+		__field(u64, error_code)
  		__field(u64 *, sptep)
  		__field(u64, old_spte)
  		__field(u64, new_spte)





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