linux-kernel - [tip: x86/fpu] x86/fpu: Drop @perm from guest pseudo FPU container

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Message-ID: <174652563422.406.4328703554427720603.tip-bot2@tip-bot2>
Date: Tue, 06 May 2025 10:00:34 -0000
From: "tip-bot2 for Chao Gao" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Maxim Levitsky <mlevitsk@...hat.com>, Chao Gao <chao.gao@...el.com>,
 Ingo Molnar <mingo@...nel.org>, "Chang S. Bae" <chang.seok.bae@...el.com>,
 Andy Lutomirski <luto@...nel.org>, David Woodhouse <dwmw2@...radead.org>,
 Eric Biggers <ebiggers@...gle.com>, Fenghua Yu <fenghua.yu@...el.com>,
 "H. Peter Anvin" <hpa@...or.com>, Kees Cook <kees@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Mitchell Levy <levymitchell0@...il.com>, Oleg Nesterov <oleg@...hat.com>,
 Paolo Bonzini <pbonzini@...hat.com>,
 Samuel Holland <samuel.holland@...ive.com>,
 Sean Christopherson <seanjc@...gle.com>,
 Vitaly Kuznetsov <vkuznets@...hat.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu: Drop @perm from guest pseudo FPU container

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     32d5fa804dc9bd7cf6651a1378ba616d332e7444
Gitweb:        https://git.kernel.org/tip/32d5fa804dc9bd7cf6651a1378ba616d332e7444
Author:        Chao Gao <chao.gao@...el.com>
AuthorDate:    Tue, 06 May 2025 17:36:07 +08:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 06 May 2025 11:52:22 +02:00

x86/fpu: Drop @perm from guest pseudo FPU container

Remove @perm from the guest pseudo FPU container. The field is
initialized during allocation and never used later.

Rename fpu_init_guest_permissions() to show that its sole purpose is to
lock down guest permissions.

Suggested-by: Maxim Levitsky <mlevitsk@...hat.com>
Signed-off-by: Chao Gao <chao.gao@...el.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Eric Biggers <ebiggers@...gle.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <kees@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mitchell Levy <levymitchell0@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Samuel Holland <samuel.holland@...ive.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Link: https://lore.kernel.org/kvm/af972fe5981b9e7101b64de43c7be0a8cc165323.camel@redhat.com/
Link: https://lore.kernel.org/r/20250506093740.2864458-3-chao.gao@intel.com
---
 arch/x86/include/asm/fpu/types.h | 7 -------
 arch/x86/kernel/fpu/core.c       | 7 ++-----
 2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index e64db0e..1c94121 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -536,13 +536,6 @@ struct fpu_guest {
 	u64				xfeatures;
 
 	/*
-	 * @perm:			xfeature bitmap of features which are
-	 *				permitted to be enabled for the guest
-	 *				vCPU.
-	 */
-	u64				perm;
-
-	/*
 	 * @xfd_err:			Save the guest value.
 	 */
 	u64				xfd_err;
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 105b1b8..1cda5b7 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -212,7 +212,7 @@ void fpu_reset_from_exception_fixup(void)
 #if IS_ENABLED(CONFIG_KVM)
 static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
 
-static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
+static void fpu_lock_guest_permissions(void)
 {
 	struct fpu_state_perm *fpuperm;
 	u64 perm;
@@ -228,8 +228,6 @@ static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
 	WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED);
 
 	spin_unlock_irq(&current->sighand->siglock);
-
-	gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED;
 }
 
 bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
@@ -250,7 +248,6 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 
 	gfpu->fpstate		= fpstate;
 	gfpu->xfeatures		= fpu_kernel_cfg.default_features;
-	gfpu->perm		= fpu_kernel_cfg.default_features;
 
 	/*
 	 * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state
@@ -265,7 +262,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 	if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size))
 		gfpu->uabi_size = fpu_user_cfg.default_size;
 
-	fpu_init_guest_permissions(gfpu);
+	fpu_lock_guest_permissions();
 
 	return true;
 }