Merge tag 'kvm-x86-selftests-6.4' of https://github.com/kvm-x86/linux into HEAD

KVM selftests, and an AMX/XCR0 bugfix, for 6.4:

 - Don't advertise XTILE_CFG in KVM_GET_SUPPORTED_CPUID if XTILE_DATA is
   not being reported due to userspace not opting in via prctl()

 - Overhaul the AMX selftests to improve coverage and cleanup the test

 - Misc cleanups

3 files changed, 31 insertions, 4 deletions

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b944492faefa..123bf8b97a4b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -996,7 +996,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->eax = entry->ebx = entry->ecx = 0;
 		break;
 	case 0xd: {
-		u64 permitted_xcr0 = kvm_caps.supported_xcr0 & xstate_get_guest_group_perm();
+		u64 permitted_xcr0 = kvm_get_filtered_xcr0();
 		u64 permitted_xss = kvm_caps.supported_xss;
 
 		entry->eax &= permitted_xcr0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 095a41c6f346..6a41bdb7f599 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4593,9 +4593,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 			r = 0;
 		break;
 	case KVM_CAP_XSAVE2: {
-		u64 guest_perm = xstate_get_guest_group_perm();
-
-		r = xstate_required_size(kvm_caps.supported_xcr0 & guest_perm, false);
+		r = xstate_required_size(kvm_get_filtered_xcr0(), false);
 		if (r < sizeof(struct kvm_xsave))
 			r = sizeof(struct kvm_xsave);
 		break;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index fbef05c0bdeb..c544602d07a3 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -3,6 +3,7 @@
 #define ARCH_X86_KVM_X86_H
 
 #include <linux/kvm_host.h>
+#include <asm/fpu/xstate.h>
 #include <asm/mce.h>
 #include <asm/pvclock.h>
 #include "kvm_cache_regs.h"
@@ -328,6 +329,34 @@ extern struct kvm_caps kvm_caps;
 
 extern bool enable_pmu;
 
+/*
+ * Get a filtered version of KVM's supported XCR0 that strips out dynamic
+ * features for which the current process doesn't (yet) have permission to use.
+ * This is intended to be used only when enumerating support to userspace,
+ * e.g. in KVM_GET_SUPPORTED_CPUID and KVM_CAP_XSAVE2, it does NOT need to be
+ * used to check/restrict guest behavior as KVM rejects KVM_SET_CPUID{2} if
+ * userspace attempts to enable unpermitted features.
+ */
+static inline u64 kvm_get_filtered_xcr0(void)
+{
+	u64 permitted_xcr0 = kvm_caps.supported_xcr0;
+
+	BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA);
+
+	if (permitted_xcr0 & XFEATURE_MASK_USER_DYNAMIC) {
+		permitted_xcr0 &= xstate_get_guest_group_perm();
+
+		/*
+		 * Treat XTILE_CFG as unsupported if the current process isn't
+		 * allowed to use XTILE_DATA, as attempting to set XTILE_CFG in
+		 * XCR0 without setting XTILE_DATA is architecturally illegal.
+		 */
+		if (!(permitted_xcr0 & XFEATURE_MASK_XTILE_DATA))
+			permitted_xcr0 &= ~XFEATURE_MASK_XTILE_CFG;
+	}
+	return permitted_xcr0;
+}
+
 static inline bool kvm_mpx_supported(void)
 {
 	return (kvm_caps.supported_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR))