From: Xiao Guangrong Date: Tue, 21 Aug 2012 02:57:42 +0000 (+0800) Subject: KVM: x86: fix possible infinite loop caused by reexecute_instruction X-Git-Tag: v3.7-rc1~113^2~54 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=8e3d9d061b5d132217629e7b5635ff0c02488e65;p=platform%2Fkernel%2Flinux-exynos.git KVM: x86: fix possible infinite loop caused by reexecute_instruction Currently, we reexecute all unhandleable instructions if they do not access on the mmio, however, it can not work if host map the readonly memory to guest. If the instruction try to write this kind of memory, it will fault again when guest retry it, then we will goto a infinite loop: retry instruction -> write #PF -> emulation fail -> retry instruction -> ... Fix it by retrying the instruction only when it faults on the writable memory Signed-off-by: Xiao Guangrong Signed-off-by: Avi Kivity --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fb0d937..704680d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4473,6 +4473,7 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu) static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva) { gpa_t gpa; + pfn_t pfn; if (tdp_enabled) return false; @@ -4490,8 +4491,17 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva) if (gpa == UNMAPPED_GVA) return true; /* let cpu generate fault */ - if (!kvm_is_error_hva(gfn_to_hva(vcpu->kvm, gpa >> PAGE_SHIFT))) + /* + * Do not retry the unhandleable instruction if it faults on the + * readonly host memory, otherwise it will goto a infinite loop: + * retry instruction -> write #PF -> emulation fail -> retry + * instruction -> ... + */ + pfn = gfn_to_pfn(vcpu->kvm, gpa_to_gfn(gpa)); + if (!is_error_pfn(pfn)) { + kvm_release_pfn_clean(pfn); return true; + } return false; }