[PATCH 06/26] KVM: x86: Move MSR_IA32_BNDCFGS existence checks into vendor code

Sean Christopherson
2020-01-29T23:48:56Z

Move the MSR_IA32_BNDCFGS existence check into vendor code by way of
->has_virtualized_msr(). AMD does not support MPX, and given that Intel
is in the process of removing MPX, it's extremely unlikely AMD will ever
support MPX.

Note, invoking ->has_virtualized_msr() requires an extra retpoline, but
kvm_init_msr_list() is not a hot path. As alluded to above, the
motivation is to quarantine MPX as much as possible.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/svm.c | 2 ++
arch/x86/kvm/vmx/vmx.c | 2 ++
arch/x86/kvm/x86.c | 4 ----
3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 4c8427f57b71..504118c49f46 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5990,6 +5990,8 @@ static bool svm_has_virtualized_msr(u32 index)
switch (index) {
case MSR_TSC_AUX:
return boot_cpu_has(X86_FEATURE_RDTSCP);
+ case MSR_IA32_BNDCFGS:
+ return false;
default:
break;
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9588914e941e..dbeef64f7409 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6279,6 +6279,8 @@ static bool vmx_has_virtualized_msr(u32 index)
switch (index) {
case MSR_TSC_AUX:
return cpu_has_vmx_rdtscp();
+ case MSR_IA32_BNDCFGS:
+ return kvm_mpx_supported();
default:
break;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a8619c52ea86..70cbb9164088 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5237,10 +5237,6 @@ static void kvm_init_msr_list(void)
* to the guests in some cases.
*/
switch (msr_index) {
- case MSR_IA32_BNDCFGS:
- if (!kvm_mpx_supported())
- continue;
- break;
case MSR_IA32_RTIT_CTL:
case MSR_IA32_RTIT_STATUS:
if (!kvm_x86_ops->pt_supported())
--
2.24.1