Re: [PATCH] KVM: nVMX: cleanup and fix host 64-bit mode checks

From: Krish Sadhukhan
Date: Wed Sep 25 2019 - 19:55:36 EST




On 09/25/2019 09:47 AM, Jim Mattson wrote:
On Wed, Sep 25, 2019 at 9:34 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
KVM was incorrectly checking vmcs12->host_ia32_efer even if the "load
IA32_EFER" exit control was reset. Also, some checks were not using
the new CC macro for tracing.

Cleanup everything so that the vCPU's 64-bit mode is determined
directly from EFER_LMA and the VMCS checks are based on that, which
matches section 26.2.4 of the SDM.

Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Jim Mattson <jmattson@xxxxxxxxxx>
Cc: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Fixes: 5845038c111db27902bc220a4f70070fe945871c
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 53 ++++++++++++++++++++---------------------------
1 file changed, 22 insertions(+), 31 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 70d59d9304f2..e108847f6cf8 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2664,8 +2664,26 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
CC(!kvm_pat_valid(vmcs12->host_ia32_pat)))
return -EINVAL;

- ia32e = (vmcs12->vm_exit_controls &
- VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
+#ifdef CONFIG_X86_64
+ ia32e = !!(vcpu->arch.efer & EFER_LMA);
+#else
+ if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE))
+ return -EINVAL;
This check is redundant, since it is checked in the else block below.

Should we be re-using is_long_mode() instead of duplicating the code ?


+
+ ia32e = false;
+#endif
+
+ if (ia32e) {
+ if (CC(!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) ||
+ CC(!(vmcs12->host_cr4 & X86_CR4_PAE)))
+ return -EINVAL;
+ } else {
+ if (CC(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) ||
+ CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
+ CC(vmcs12->host_cr4 & X86_CR4_PCIDE) ||
+ CC(((vmcs12->host_rip) >> 32) & 0xffffffff))
The mask shouldn't be necessary.

+ return -EINVAL;
+ }

if (CC(vmcs12->host_cs_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
CC(vmcs12->host_ss_selector & (SEGMENT_RPL_MASK | SEGMENT_TI_MASK)) ||
@@ -2684,35 +2702,8 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
CC(is_noncanonical_address(vmcs12->host_gs_base, vcpu)) ||
CC(is_noncanonical_address(vmcs12->host_gdtr_base, vcpu)) ||
CC(is_noncanonical_address(vmcs12->host_idtr_base, vcpu)) ||
- CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)))
- return -EINVAL;
-
- if (!(vmcs12->host_ia32_efer & EFER_LMA) &&
- ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
- (vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE))) {
- return -EINVAL;
- }
-
- if ((vmcs12->host_ia32_efer & EFER_LMA) &&
- !(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) {
- return -EINVAL;
- }
-
- if (!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
- ((vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
- (vmcs12->host_cr4 & X86_CR4_PCIDE) ||
- (((vmcs12->host_rip) >> 32) & 0xffffffff))) {
- return -EINVAL;
- }
-
- if ((vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) &&
- ((!(vmcs12->host_cr4 & X86_CR4_PAE)) ||
- (is_noncanonical_address(vmcs12->host_rip, vcpu)))) {
- return -EINVAL;
- }
-#else
- if (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE ||
- vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)
+ CC(is_noncanonical_address(vmcs12->host_tr_base, vcpu)) ||
+ CC(is_noncanonical_address(vmcs12->host_rip, vcpu)))
return -EINVAL;
#endif

--
1.8.3.1

Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>