linux-kernel - [PATCH v4 16/15] fixup! KVM: SEV: sync FPU and AVX state at LAUNCH_UPDATE

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Date: Tue, 19 Mar 2024 15:43:55 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: michael.roth@....com,
	seanjc@...gle.com
Subject: [PATCH v4 16/15] fixup! KVM: SEV: sync FPU and AVX state at LAUNCH_UPDATE_VMSA time

A small change to add EXPORT_SYMBOL_GPL, and especially to actually match
the format in which the processor expects x87 registers in the VMSA.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kernel/fpu/xstate.c |  1 +
 arch/x86/kvm/svm/sev.c       | 12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 117e74c44e75..eeaf4ec9243d 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -990,6 +990,7 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 
 	return __raw_xsave_addr(xsave, xfeature_nr);
 }
+EXPORT_SYMBOL_GPL(get_xsave_addr);
 
 #ifdef CONFIG_ARCH_HAS_PKEYS
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index cee6beb2bf29..66fa852b48b3 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -679,9 +679,17 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
 	save->x87_rip = xsave->i387.rip;
 
 	for (i = 0; i < 8; i++) {
-		d = save->fpreg_x87 + i * 10;
+		/*
+		 * The format of the x87 save area is totally undocumented,
+		 * and definitely not what you would expect.  It consists
+		 * of an 8*8 bytes area with bytes 0-7 and an 8*2 bytes area
+		 * with bytes 8-9 of each register.
+		 */
+		d = save->fpreg_x87 + i * 8;
 		s = ((u8 *)xsave->i387.st_space) + i * 16;
-		memcpy(d, s, 10);
+		memcpy(d, s, 8);
+		save->fpreg_x87[64 + i * 2] = s[8];
+		save->fpreg_x87[64 + i * 2 + 1] = s[9];
 	}
 	memcpy(save->fpreg_xmm, xsave->i387.xmm_space, 256);
 
-- 
2.43.0