linux-kernel - [PATCH v6a 6/8] x86/fpu: Remove xfd argument from __fpstate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250509081615.248896-1-chao.gao@intel.com>
Date: Fri,  9 May 2025 01:16:15 -0700
From: Chao Gao <chao.gao@...el.com>
To: chao.gao@...el.com
Cc: bp@...en8.de,
	chang.seok.bae@...el.com,
	dave.hansen@...el.com,
	dave.hansen@...ux.intel.com,
	ebiggers@...gle.com,
	hpa@...or.com,
	john.allen@....com,
	kees@...nel.org,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mingo@...hat.com,
	oleg@...hat.com,
	pbonzini@...hat.com,
	peterz@...radead.org,
	rick.p.edgecombe@...el.com,
	seanjc@...gle.com,
	stanspas@...zon.de,
	tglx@...utronix.de,
	weijiang.yang@...el.com,
	x86@...nel.org,
	xin3.li@...el.com
Subject: [PATCH v6a 6/8] x86/fpu: Remove xfd argument from __fpstate_reset()

The initial values for fpstate::xfd differ between guest and host fpstates.
Currently, the initial values are passed as an argument to
__fpstate_reset(). But, __fpstate_reset() already assigns different default
features and sizes based on the type of fpstates (i.e., guest or host). So,
handle fpstate::xfd in a similar way to highlight the differences in the
initial xfd value between guest and host fpstates

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Chao Gao <chao.gao@...el.com>
Link: https://lore.kernel.org/all/aBuf7wiiDT0Wflhk@google.com/
---
v6a: new.

Note: this quick revision is just intended to ensure that the feedback
has been properly addressed.

 arch/x86/kernel/fpu/core.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 0d501bd25d79..a3cafed350e0 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -211,7 +211,7 @@ void fpu_reset_from_exception_fixup(void)
 }
 
 #if IS_ENABLED(CONFIG_KVM)
-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
+static void __fpstate_reset(struct fpstate *fpstate);
 
 static void fpu_lock_guest_permissions(void)
 {
@@ -246,8 +246,7 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
 	fpstate->is_valloc	= true;
 	fpstate->is_guest	= true;
 
-	/* Leave xfd to 0 (the reset value defined by spec) */
-	__fpstate_reset(fpstate, 0);
+	__fpstate_reset(fpstate);
 	fpstate_init_user(fpstate);
 
 	gfpu->fpstate		= fpstate;
@@ -536,7 +535,7 @@ void fpstate_init_user(struct fpstate *fpstate)
 		fpstate_init_fstate(fpstate);
 }
 
-static void __fpstate_reset(struct fpstate *fpstate, u64 xfd)
+static void __fpstate_reset(struct fpstate *fpstate)
 {
 	/*
 	 * Initialize sizes and feature masks. Supervisor features and
@@ -546,21 +545,23 @@ static void __fpstate_reset(struct fpstate *fpstate, u64 xfd)
 	if (fpstate->is_guest) {
 		fpstate->size		= guest_default_cfg.size;
 		fpstate->xfeatures	= guest_default_cfg.features;
+		/* Leave xfd to 0 (the reset value defined by spec) */
+		fpstate->xfd		= 0;
 	} else {
 		fpstate->size		= fpu_kernel_cfg.default_size;
 		fpstate->xfeatures	= fpu_kernel_cfg.default_features;
+		fpstate->xfd		= init_fpstate.xfd;
 	}
 
 	fpstate->user_size	= fpu_user_cfg.default_size;
 	fpstate->user_xfeatures	= fpu_user_cfg.default_features;
-	fpstate->xfd		= xfd;
 }
 
 void fpstate_reset(struct fpu *fpu)
 {
 	/* Set the fpstate pointer to the default fpstate */
 	fpu->fpstate = &fpu->__fpstate;
-	__fpstate_reset(fpu->fpstate, init_fpstate.xfd);
+	__fpstate_reset(fpu->fpstate);
 
 	/* Initialize the permission related info in fpu */
 	fpu->perm.__state_perm		= fpu_kernel_cfg.default_features;
-- 
2.47.1