linux-kernel - [PATCH tip/x86/fpu 6/6] x86/fpu: shift fpregs_assert_state_consistent() from arch_exit

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Message-ID: <20250503143902.GA9012@redhat.com>
Date: Sat, 3 May 2025 16:39:02 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...capital.net>,
	Dave Hansen <dave@...1.net>, Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Chang S . Bae" <chang.seok.bae@...el.com>
Subject: [PATCH tip/x86/fpu 6/6] x86/fpu: shift
 fpregs_assert_state_consistent() from arch_exit_work() to its caller

If CONFIG_X86_DEBUG_FPU=Y, arch_exit_to_user_mode_prepare() calls
arch_exit_work() even if ti_work == 0. There only reason is that we
want to call fpregs_assert_state_consistent() if TIF_NEED_FPU_LOAD
is not set.

This looks confusing. arch_exit_to_user_mode_prepare() can just call
fpregs_assert_state_consistent() unconditionally, it depends on
CONFIG_X86_DEBUG_FPU and checks TIF_NEED_FPU_LOAD itself.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/include/asm/entry-common.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h
index 77d20555e04d..d535a97c7284 100644
--- a/arch/x86/include/asm/entry-common.h
+++ b/arch/x86/include/asm/entry-common.h
@@ -53,7 +53,6 @@ static inline void arch_exit_work(unsigned long ti_work)
 	if (unlikely(ti_work & _TIF_IO_BITMAP))
 		tss_update_io_bitmap();
 
-	fpregs_assert_state_consistent();
 	if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
 		switch_fpu_return();
 }
@@ -61,7 +60,9 @@ static inline void arch_exit_work(unsigned long ti_work)
 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
 						  unsigned long ti_work)
 {
-	if (IS_ENABLED(CONFIG_X86_DEBUG_FPU) || unlikely(ti_work))
+	fpregs_assert_state_consistent();
+
+	if (unlikely(ti_work))
 		arch_exit_work(ti_work);
 
 	fred_update_rsp0();
-- 
2.25.1.362.g51ebf55