Merge tag 'kvm-arm-fixes-for-v4.19-v2' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6-block.git] / arch / x86 / kvm / mmu.c

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index d440154e8938ccf9dfb8c6749475cea4085d199a..e24ea7067373af69d258c46995007b0446a69fdc 100644 (file)
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5212,7 +5212,7 @@ 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 = EMULTYPE_RETRY;
+       int r, emulation_type = 0;
        enum emulation_result er;
        bool direct = vcpu->arch.mmu.direct_map;
 
@@ -5225,10 +5225,8 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
        r = RET_PF_INVALID;
        if (unlikely(error_code & PFERR_RSVD_MASK)) {
                r = handle_mmio_page_fault(vcpu, cr2, direct);
-               if (r == RET_PF_EMULATE) {
-                       emulation_type = 0;
+               if (r == RET_PF_EMULATE)
                        goto emulate;
-               }
        }
 
        if (r == RET_PF_INVALID) {
@@ -5255,8 +5253,19 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
                return 1;
        }
 
-       if (mmio_info_in_cache(vcpu, cr2, direct))
-               emulation_type = 0;
+       /*
+        * vcpu->arch.mmu.page_fault returned RET_PF_EMULATE, but we can still
+        * optimistically try to just unprotect the page and let the processor
+        * re-execute the instruction that caused the page fault.  Do not allow
+        * retrying MMIO emulation, as it's not only pointless but could also
+        * cause us to enter an infinite loop because the processor will keep
+        * faulting on the non-existent MMIO address.  Retrying an instruction
+        * from a nested guest is also pointless and dangerous as we are only
+        * explicitly shadowing L1's page tables, i.e. unprotecting something
+        * 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;
 emulate:
        /*
         * On AMD platforms, under certain conditions insn_len may be zero on #NPF.