[PATCH 25/26] KVM: x86: Handle main Intel PT CPUID leaf in vendor code

Sean Christopherson
2020-01-29T23:47:12Z

Move the clearing of the Intel PT CPUID leaf into vendor code to
eliminate a call to ->pt_supported(). To handle clearing CPUID 0x14's
index>0 sub-leafs, introduce the pattern of adding feature-dependent
sub-leafs (index>0 sub-leafs whose existence is enumerated by index=0)
after calling ->set_supported_cpuid(). The dependent sub-leafs pattern
can be reused for future (Intel) features such as SGX to allow vendor
code to disable the feature, e.g. via module param, without having to
add a feature specific kvm_x86_ops hook.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/cpuid.c | 32 ++++++++++++++++----------------
arch/x86/kvm/svm.c | 3 +++
arch/x86/kvm/vmx/vmx.c | 4 ++++
3 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d06fb54c9c0d..ca766c460318 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -409,7 +409,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
unsigned f_gbpages = 0;
unsigned f_lm = 0;
#endif
- unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;

/* cpuid 1.edx */
const u32 kvm_cpuid_1_edx_x86_features =
@@ -648,22 +647,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
break;
}
/* Intel PT */
- case 0x14: {
- int t, times = entry->eax;
-
- if (!f_intel_pt) {
- entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
- break;
- }
-
- for (t = 1; t <= times; ++t) {
- if (*nent >= maxnent)
- goto out;
- do_host_cpuid(&entry[t], function, t);
- ++*nent;
- }
+ case 0x14:
break;
- }
case KVM_CPUID_SIGNATURE: {
static const char signature[12] = "KVMKVMKVM\0\0";
const u32 *sigptr = (const u32 *)signature;
@@ -778,6 +763,21 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,

kvm_x86_ops->set_supported_cpuid(entry);

+ /*
+ * Add feature-dependent sub-leafs after ->set_supported_cpuid() to
+ * properly handle the feature being disabled by SVM/VMX.
+ */
+ if (function == 0x14) {
+ int t, times = entry->eax;
+
+ for (t = 1; t <= times; ++t) {
+ if (*nent >= maxnent)
+ goto out;
+ do_host_cpuid(&entry[t], function, t);
+ ++*nent;
+ }
+ }
+
r = 0;

out:
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 350cdf91a576..a08ee7b2dddb 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6068,6 +6068,9 @@ static void svm_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
cpuid_entry_clear(entry, X86_FEATURE_INVPCID);
cpuid_entry_clear(entry, X86_FEATURE_INTEL_PT);
break;
+ case 0x14:
+ entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+ break;
case 0x80000001:
if (nested)
cpuid_entry_set(entry, X86_FEATURE_SVM);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 35134dbed2f0..10c31aa40730 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7155,6 +7155,10 @@ static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
if (vmx_umip_emulated())
cpuid_entry_set(entry, X86_FEATURE_UMIP);
break;
+ case 0x14:
+ if (!vmx_pt_mode_is_host_guest())
+ entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+ break;
case 0x80000001:
if (!cpu_has_vmx_rdtscp())
cpuid_entry_clear(entry, X86_FEATURE_RDTSCP);
--
2.24.1