linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, jannh@google.com, riel@surriel.com,
	mingo@redhat.com, bp@suse.de, Jason@zx2c4.com, luto@kernel.org,
	tglx@linutronix.de, rkrcmar@redhat.com, mingo@kernel.org,
	hpa@zytor.com, kvm@vger.kernel.org, pbonzini@redhat.com,
	kurt.kanzenbach@linutronix.de,
	Dave Hansen <dave.hansen@intel.com>
Subject: [PATCH] x86/fpu: Remove unneeded saving of FPU registers in copy_fpstate_to_sigframe()
Date: Tue, 30 Apr 2019 10:31:26 +0200	[thread overview]
Message-ID: <20190430083126.rilbb76yc27vrem5@linutronix.de> (raw)

Since commit

  eeec00d73be2e ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails")

there is no need to have FPU registers saved if
copy_fpregs_to_sigframe() fails because we retry it after we resolved
the fault condition.
Saving the registers is not wrong but it is not needed and it forces us
to load the FPU registers on the retry attempt.

Don't save the FPU registers if copy_fpstate_to_sigframe() fails.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 9834ff8b570b7..eaddb185cac95 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -134,10 +134,9 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
  */
 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 {
-	struct fpu *fpu = &current->thread.fpu;
 	struct task_struct *tsk = current;
 	int ia32_fxstate = (buf != buf_fx);
-	int ret = -EFAULT;
+	int ret;
 
 	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -164,9 +163,6 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 	pagefault_disable();
 	ret = copy_fpregs_to_sigframe(buf_fx);
 	pagefault_enable();
-	if (ret && !test_thread_flag(TIF_NEED_FPU_LOAD))
-		copy_fpregs_to_fpstate(fpu);
-	set_thread_flag(TIF_NEED_FPU_LOAD);
 	fpregs_unlock();
 
 	if (ret) {
-- 
2.20.1


             reply	other threads:[~2019-04-30  8:31 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-30  8:31 Sebastian Andrzej Siewior [this message]
2019-04-30 11:30 ` [tip:x86/fpu] x86/fpu: Remove unnecessary " tip-bot for Sebastian Andrzej Siewior

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190430083126.rilbb76yc27vrem5@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=Jason@zx2c4.com \
    --cc=bp@suse.de \
    --cc=dave.hansen@intel.com \
    --cc=hpa@zytor.com \
    --cc=jannh@google.com \
    --cc=kurt.kanzenbach@linutronix.de \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mingo@kernel.org \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=riel@surriel.com \
    --cc=rkrcmar@redhat.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] x86/fpu: Remove unneeded saving of FPU registers in copy_fpstate_to_sigframe()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).