KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED_CPUID

From: Like Xu <[email protected]>

With the help of xstate_get_guest_group_perm(), KVM can exclude unpermitted xfeatures in cpuid.0xd.0.eax, in which case the corresponding xfeatures sizes should also be matched to the permitted xfeatures.

To fix this inconsistency, the permitted_xcr0 and permitted_xss are defined consistently, which implies 'supported' plus certain permissions for this task, and it also fixes cpuid.0xd.1.ebx and later leaf-by-leaf queries.

Fixes 445ecdf79be0 ("kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID")

Signed-off-by Like Xu <[email protected]>

---
v1 -> v2 Changelog:
- Drop the use of shadow variable; (Paolo)
- Define permitted_xss consistently; (Kevin)

Previous:
https://lore.kernel.org/kvm/[email protected]/

  arch/x86/kvm/cpuid.c | 25 +++++++++++++------------
  1 file changed, 13 insertions(+), 12 deletions(-)

arch/x86/kvm/cpuid.c +12 -11

index 3902c28fb6cb..07844d15dfdf 100644
@@ -887,13 +887,14 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
  		}
  		break;
  	case 0xd: {
-		u64 guest_perm = xstate_get_guest_group_perm();
+		u64 permitted_xcr0 = supported_xcr0 & xstate_get_guest_group_perm();
+		u64 permitted_xss = supported_xss;
 
-		entry->eax &= supported_xcr0 & guest_perm;
-		entry->ebx = xstate_required_size(supported_xcr0, false);
+		entry->eax &= permitted_xcr0;
+		entry->ebx = xstate_required_size(permitted_xcr0, false);
  		entry->ecx = entry->ebx;
-		entry->edx &= (supported_xcr0 & guest_perm) >> 32;
-		if (!supported_xcr0)
+		entry->edx &= permitted_xcr0 >> 32;
+		if (!permitted_xcr0)
  			break;
 
  		entry = do_host_cpuid(array, function, 1);

@@ -902,20 +903,20 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 
  		cpuid_entry_override(entry, CPUID_D_1_EAX);
  		if (entry->eax & (F(XSAVES)|F(XSAVEC)))
-			entry->ebx = xstate_required_size(supported_xcr0 | supported_xss,
+			entry->ebx = xstate_required_size(permitted_xcr0 | permitted_xss,
  							  true);
  		else {
-			WARN_ON_ONCE(supported_xss != 0);
+			WARN_ON_ONCE(permitted_xss != 0);
  			entry->ebx = 0;
  		}
-		entry->ecx &= supported_xss;
-		entry->edx &= supported_xss >> 32;
+		entry->ecx &= permitted_xss;
+		entry->edx &= permitted_xss >> 32;
 
  		for (i = 2; i < 64; ++i) {
  			bool s_state;
-			if (supported_xcr0 & BIT_ULL(i))
+			if (permitted_xcr0 & BIT_ULL(i))
  				s_state = false;
-			else if (supported_xss & BIT_ULL(i))
+			else if (permitted_xss & BIT_ULL(i))
  				s_state = true;
  			else
  				continue;