On Sat, 18 Apr 2020 at 00:39, Paolo Bonzini pbonzini@redhat.com wrote:
When a nested page fault is taken from an address that does not have a memslot associated to it, kvm_mmu_do_page_fault returns RET_PF_EMULATE (via mmu_set_spte) and kvm_mmu_page_fault then invokes svm_need_emulation_on_page_fault.
The default answer there is to return false, but in this case this just causes the page fault to be retried ad libitum. Since this is not a fast path, and the only other case where it is taken is an erratum, just stick a kvm_vcpu_gfn_to_memslot check in there to detect the common case where the erratum is not happening.
This fixes an infinite loop in the new set_memory_region_test.
Fixes: 05d5a4863525 ("KVM: SVM: Workaround errata#1096 (insn_len maybe zero on SMAP violation)") Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com
arch/x86/kvm/svm/svm.c | 7 +++++++ virt/kvm/kvm_main.c | 1 + 2 files changed, 8 insertions(+)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a91e397d6750..c86f7278509b 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3837,6 +3837,13 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu) bool smap = cr4 & X86_CR4_SMAP; bool is_user = svm_get_cpl(vcpu) == 3;
/** If RIP is invalid, go ahead with emulation which will cause an* internal error exit.*/if (!kvm_vcpu_gfn_to_memslot(vcpu, kvm_rip_read(vcpu) >> PAGE_SHIFT))return true;/* * Detect and workaround Errata 1096 Fam_17h_00_0Fh. *diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index e2f60e313c87..e7436d054305 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1602,6 +1602,7 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn { return __gfn_to_memslot(kvm_vcpu_memslots(vcpu), gfn); } +EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot);
This commit incurs the linux guest fails to boot once add --overcommit cpu-pm=on or not intercept hlt instruction, any thoughts?
<...>-35787 [038] .... 2825.959082: kvm_exit: vcpu 1 reason npf rip 0xfd11d info 100000014 fd000 <...>-35788 [037] .... 2825.959082: kvm_exit: vcpu 2 reason npf rip 0xfd11d info 100000014 fd000 <...>-35789 [036] .... 2825.959082: kvm_exit: vcpu 3 reason npf rip 0xfd11d info 100000014 fd000 <...>-35788 [037] .... 2825.959082: kvm_page_fault: address fd000 error_code 14 <...>-35789 [036] .... 2825.959082: kvm_page_fault: address fd000 error_code 14 <...>-35787 [038] .... 2825.959083: kvm_page_fault: address fd000 error_code 14 <...>-35788 [037] .... 2825.959086: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35788 [037] .... 2825.959086: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35789 [036] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35789 [036] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35788 [037] .... 2825.959087: kvm_fpu: unload <...>-35787 [038] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) <...>-35787 [038] .... 2825.959087: kvm_emulate_insn: 0:fd11d: (prot32) failed <...>-35789 [036] .... 2825.959087: kvm_fpu: unload <...>-35787 [038] .... 2825.959088: kvm_fpu: unload <...>-35788 [037] .... 2825.959088: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17) <...>-35789 [036] .... 2825.959089: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17) <...>-35787 [038] .... 2825.959089: kvm_userspace_exit: reason KVM_EXIT_INTERNAL_ERROR (17)