From: Paolo Bonzini pbonzini@redhat.com
[ Upstream commit 2b27924bb1d48e3775f432b70bdad5e6dd4e7798 ]
The remaining failures of vmx.flat when EPT is disabled are caused by incorrectly reflecting VMfails to the L1 hypervisor. What happens is that nested_vmx_restore_host_state corrupts the guest CR3, reloading it with the host's shadow CR3 instead, because it blindly loads GUEST_CR3 from the vmcs01.
For simplicity let's just always use hardware VMCS checks when EPT is disabled. This way, nested_vmx_restore_host_state is not reached at all (or at least shouldn't be reached).
Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/uapi/asm/vmx.h | 1 + arch/x86/kvm/vmx/nested.c | 22 ++++++++++++++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h index f0b0c90dd398..d213ec5c3766 100644 --- a/arch/x86/include/uapi/asm/vmx.h +++ b/arch/x86/include/uapi/asm/vmx.h @@ -146,6 +146,7 @@
#define VMX_ABORT_SAVE_GUEST_MSR_FAIL 1 #define VMX_ABORT_LOAD_HOST_PDPTE_FAIL 2 +#define VMX_ABORT_VMCS_CORRUPTED 3 #define VMX_ABORT_LOAD_HOST_MSR_FAIL 4
#endif /* _UAPIVMX_H */ diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index f90b3a948291..c1de052d8748 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3790,8 +3790,18 @@ static void nested_vmx_restore_host_state(struct kvm_vcpu *vcpu) vmx_set_cr4(vcpu, vmcs_readl(CR4_READ_SHADOW));
nested_ept_uninit_mmu_context(vcpu); - vcpu->arch.cr3 = vmcs_readl(GUEST_CR3); - __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail); + + /* + * This is only valid if EPT is in use, otherwise the vmcs01 GUEST_CR3 + * points to shadow pages! Fortunately we only get here after a WARN_ON + * if EPT is disabled, so a VMabort is perfectly fine. + */ + if (enable_ept) { + vcpu->arch.cr3 = vmcs_readl(GUEST_CR3); + __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail); + } else { + nested_vmx_abort(vcpu, VMX_ABORT_VMCS_CORRUPTED); + }
/* * Use ept_save_pdptrs(vcpu) to load the MMU's cached PDPTRs @@ -5739,6 +5749,14 @@ __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *)) { int i;
+ /* + * Without EPT it is not possible to restore L1's CR3 and PDPTR on + * VMfail, because they are not available in vmcs01. Just always + * use hardware checks. + */ + if (!enable_ept) + nested_early_check = 1; + if (!cpu_has_vmx_shadow_vmcs()) enable_shadow_vmcs = 0; if (enable_shadow_vmcs) {