Add a new emulation type flag to explicitly mark emulation related to a
page fault. Use the new flag, EMULTYPE_PF, to move the propagation of
the GPA into the emulator context from the page fault handler into
x86_emulate_instruction.
Similarly, to help clarify how cr2 is used, don't propagate cr2 into the
exception.address when it's *not* valid and instead explicitly zero out
exception.address. Functionally this is a nop, as all non-EMULTYPE_PF
callers pass zero for cr2, i.e. it's effectively a documentation update.
Zeroing exception.address is probably unnecessary as it shouldn't be
exposed to the guest for non-#PF exceptions, but keep the current
behavior to avoid introducing an unintentional function change.
Append _PF to EMULTYPE_ALLOW_RETRY to make it clear retrying is only
intended for use when emulating after a #PF, and add WARNs to enforce
that notion.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 12 +++++++++---
arch/x86/kvm/mmu/mmu.c | 10 ++--------
arch/x86/kvm/x86.c | 25 +++++++++++++++++++------
3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b79cd6aa4075..6311fffbc2f0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1347,8 +1347,9 @@ extern u64 kvm_mce_cap_supported;
* decode the instruction length. For use *only* by
* kvm_x86_ops->skip_emulated_instruction() implementations.
*
- * EMULTYPE_ALLOW_RETRY - Set when the emulator should resume the guest to
- * retry native execution under certain conditions.
+ * EMULTYPE_ALLOW_RETRY_PF - Set when the emulator should resume the guest to
+ * retry native execution under certain conditions,
+ * Can only be set in conjunction with EMULTYPE_PF.
*
* EMULTYPE_TRAP_UD_FORCED - Set when emulating an intercepted #UD that was
* triggered by KVM's magic "force emulation" prefix,
@@ -1361,13 +1362,18 @@ extern u64 kvm_mce_cap_supported;
* backdoor emulation, which is opt in via module param.
* VMware backoor emulation handles select instructions
* and reinjects the #GP for all other cases.
+ *
+ * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which
+ * case the CR2/GPA value pass on the stack is valid.
*/
#define EMULTYPE_NO_DECODE (1 << 0)
#define EMULTYPE_TRAP_UD (1 << 1)
#define EMULTYPE_SKIP (1 << 2)
-#define EMULTYPE_ALLOW_RETRY (1 << 3)
+#define EMULTYPE_ALLOW_RETRY_PF (1 << 3)
#define EMULTYPE_TRAP_UD_FORCED (1 << 4)
#define EMULTYPE_VMWARE_GP (1 << 5)
+#define EMULTYPE_PF (1 << 6)
+
int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
void *insn, int insn_len);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6f92b40d798c..fa49d9971b59 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5519,15 +5519,9 @@ static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
void *insn, int insn_len)
{
- int r, emulation_type = 0;
+ int r, emulation_type = EMULTYPE_PF;
bool direct = vcpu->arch.mmu->direct_map;
- /* With shadow page tables, fault_address contains a GVA or nGPA. */
- if (vcpu->arch.mmu->direct_map) {
- vcpu->arch.gpa_available = true;
- vcpu->arch.gpa_val = cr2;
- }
-
r = RET_PF_INVALID;
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, cr2, direct);
@@ -5572,7 +5566,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
* for L1 isn't going to magically fix whatever issue cause L2 to fail.
*/
if (!mmio_info_in_cache(vcpu, cr2, direct) && !is_guest_mode(vcpu))
- emulation_type = EMULTYPE_ALLOW_RETRY;
+ emulation_type |= EMULTYPE_ALLOW_RETRY_PF;
emulate:
/*
* On AMD platforms, under certain conditions insn_len may be zero on #NPF.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a256e09f321a..848e4ec21c5e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6393,10 +6393,11 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2,
gpa_t gpa = cr2;
kvm_pfn_t pfn;
- if (!(emulation_type & EMULTYPE_ALLOW_RETRY))
+ if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
return false;
- if (WARN_ON_ONCE(is_guest_mode(vcpu)))
+ if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
+ WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
return false;
if (!vcpu->arch.mmu->direct_map) {
@@ -6484,10 +6485,11 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
*/
vcpu->arch.last_retry_eip = vcpu->arch.last_retry_addr = 0;
- if (!(emulation_type & EMULTYPE_ALLOW_RETRY))
+ if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
return false;
- if (WARN_ON_ONCE(is_guest_mode(vcpu)))
+ if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
+ WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
return false;
if (x86_page_table_writing_insn(ctxt))
@@ -6742,8 +6744,19 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
}
restart:
- /* Save the faulting GPA (cr2) in the address field */
- ctxt->exception.address = cr2;
+ if (emulation_type & EMULTYPE_PF) {
+ /* Save the faulting GPA (cr2) in the address field */
+ ctxt->exception.address = cr2;
+
+ /* With shadow page tables, cr2 contains a GVA or nGPA. */
+ if (vcpu->arch.mmu->direct_map) {
+ vcpu->arch.gpa_available = true;
+ vcpu->arch.gpa_val = cr2;
+ }
+ } else {
+ /* Sanitize the address out of an abundance of paranoia. */
+ ctxt->exception.address = 0;
+ }
r = x86_emulate_insn(ctxt);
--
2.24.0
