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@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
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);
bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
--
2.18.2
