x86/kvm: Avoid looking up PKRU in XSAVE buffer

mainline inclusion
from mainline-v5.14-rc1
commit 71ef4533
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I590ZC
CVE: NA

Intel-SIG: commit 71ef4533 x86/kvm: Avoid looking up PKRU in XSAVE buffer.

--------------------------------

PKRU is being removed from the kernel XSAVE/FPU buffers.  This removal
will probably include warnings for code that look up PKRU in those
buffers.

KVM currently looks up the location of PKRU but doesn't even use the
pointer that it gets back.  Rework the code to avoid calling
get_xsave_addr() except in cases where its result is actually used.

This makes the code more clear and also avoids the inevitable PKRU
warnings.

This is probably a good cleanup and could go upstream idependently
of any PKRU rework.
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Reviewed-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.541037562@linutronix.deSigned-off-by: NLin Wang <lin.x.wang@intel.com>
Signed-off-by: NAichun Shi <aichun.shi@intel.com>

arch/x86/kvm/x86.c

@@ -4602,20 +4602,21 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
 	 */
 	valid = xstate_bv & ~XFEATURE_MASK_FPSSE;
 	while (valid) {
+		u32 size, offset, ecx, edx;
 		u64 xfeature_mask = valid & -valid;
 		int xfeature_nr = fls64(xfeature_mask) - 1;
-		void *src = get_xsave_addr(xsave, xfeature_nr);
-
-		if (src) {
-			u32 size, offset, ecx, edx;
-			cpuid_count(XSTATE_CPUID, xfeature_nr,
-				    &size, &offset, &ecx, &edx);
-			if (xfeature_nr == XFEATURE_PKRU)
-				memcpy(dest + offset, &vcpu->arch.pkru,
-				       sizeof(vcpu->arch.pkru));
-			else
-				memcpy(dest + offset, src, size);
+		void *src;
+
+		cpuid_count(XSTATE_CPUID, xfeature_nr,
+			    &size, &offset, &ecx, &edx);
 
+		if (xfeature_nr == XFEATURE_PKRU) {
+			memcpy(dest + offset, &vcpu->arch.pkru,
+			       sizeof(vcpu->arch.pkru));
+		} else {
+			src = get_xsave_addr(xsave, xfeature_nr);
+			if (src)
+				memcpy(dest + offset, src, size);
 		}
 
 		valid -= xfeature_mask;
@@ -4645,18 +4646,20 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)
 	 */
 	valid = xstate_bv & ~XFEATURE_MASK_FPSSE;
 	while (valid) {
+		u32 size, offset, ecx, edx;
 		u64 xfeature_mask = valid & -valid;
 		int xfeature_nr = fls64(xfeature_mask) - 1;
-		void *dest = get_xsave_addr(xsave, xfeature_nr);
-
-		if (dest) {
-			u32 size, offset, ecx, edx;
-			cpuid_count(XSTATE_CPUID, xfeature_nr,
-				    &size, &offset, &ecx, &edx);
-			if (xfeature_nr == XFEATURE_PKRU)
-				memcpy(&vcpu->arch.pkru, src + offset,
-				       sizeof(vcpu->arch.pkru));
-			else
+
+		cpuid_count(XSTATE_CPUID, xfeature_nr,
+			    &size, &offset, &ecx, &edx);
+
+		if (xfeature_nr == XFEATURE_PKRU) {
+			memcpy(&vcpu->arch.pkru, src + offset,
+			       sizeof(vcpu->arch.pkru));
+		} else {
+			void *dest = get_xsave_addr(xsave, xfeature_nr);
+
+			if (dest)
 				memcpy(dest, src + offset, size);
 		}