linux-kernel - [PATCH v4 6/8] x86/fpu: Initialize guest fpstate and FPU pseudo container from guest defaults

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Message-ID: <20250318153316.1970147-7-chao.gao@intel.com>
Date: Tue, 18 Mar 2025 23:31:56 +0800
From: Chao Gao <chao.gao@...el.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	tglx@...utronix.de,
	dave.hansen@...el.com,
	seanjc@...gle.com,
	pbonzini@...hat.com
Cc: peterz@...radead.org,
	rick.p.edgecombe@...el.com,
	weijiang.yang@...el.com,
	john.allen@....com,
	bp@...en8.de,
	chang.seok.bae@...el.com,
	xin3.li@...el.com,
	Chao Gao <chao.gao@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Stanislav Spassov <stanspas@...zon.de>,
	Uros Bizjak <ubizjak@...il.com>,
	Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH v4 6/8] x86/fpu: Initialize guest fpstate and FPU pseudo container from guest defaults

fpu_alloc_guest_fpstate() currently uses host defaults to initialize guest
fpstate and pseudo containers. Guest defaults were introduced to
differentiate the features and sizes of host and guest FPUs. Update the
function to use guest defaults instead.

Signed-off-by: Chao Gao <chao.gao@...el.com>
---
 arch/x86/kernel/fpu/core.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 52df97a8a61b..b00e4032d75f 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -200,7 +200,16 @@ void fpu_reset_from_exception_fixup(void)
 }
 
 #if IS_ENABLED(CONFIG_KVM)
-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
+static void __guest_fpstate_reset(struct fpstate *fpstate, u64 xfd)
+{
+	/* Initialize sizes and feature masks */
+	fpstate->size		= fpu_kernel_cfg.guest_default_size;
+	fpstate->user_size	= fpu_user_cfg.guest_default_size;
+	fpstate->xfeatures	= fpu_kernel_cfg.guest_default_features;
+	fpstate->user_xfeatures	= fpu_user_cfg.guest_default_features;
+	fpstate->xfd		= xfd;
+}
+
 
 static void fpu_lock_guest_permissions(struct fpu_guest *gfpu)
 {
@@ -225,19 +234,21 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 	struct fpstate *fpstate;
 	unsigned int size;
 
-	size = fpu_kernel_cfg.default_size + ALIGN(offsetof(struct fpstate, regs), 64);
+	size = fpu_kernel_cfg.guest_default_size +
+	       ALIGN(offsetof(struct fpstate, regs), 64);
+
 	fpstate = vzalloc(size);
 	if (!fpstate)
 		return false;
 
 	/* Leave xfd to 0 (the reset value defined by spec) */
-	__fpstate_reset(fpstate, 0);
+	__guest_fpstate_reset(fpstate, 0);
 	fpstate_init_user(fpstate);
 	fpstate->is_valloc	= true;
 	fpstate->is_guest	= true;
 
 	gfpu->fpstate		= fpstate;
-	gfpu->xfeatures		= fpu_kernel_cfg.default_features;
+	gfpu->xfeatures		= fpu_kernel_cfg.guest_default_features;
 
 	/*
 	 * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state
@@ -249,8 +260,8 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 	 * all features that can expand the uABI size must be opt-in.
 	 */
 	gfpu->uabi_size		= sizeof(struct kvm_xsave);
-	if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size))
-		gfpu->uabi_size = fpu_user_cfg.default_size;
+	if (WARN_ON_ONCE(fpu_user_cfg.guest_default_size > gfpu->uabi_size))
+		gfpu->uabi_size = fpu_user_cfg.guest_default_size;
 
 	fpu_lock_guest_permissions(gfpu);
 
-- 
2.46.1