From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, "Andy Lutomirski" <luto@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
"Rik van Riel" <riel@surriel.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Borislav Petkov" <bp@suse.de>
Subject: [PATCH 03/24] x86/fpu: Remove preempt_disable() in fpu__clear()
Date: Thu, 21 Mar 2019 21:26:11 +0100 [thread overview]
Message-ID: <20190321202632.16810-4-bigeasy@linutronix.de> (raw)
In-Reply-To: <20190321202632.16810-1-bigeasy@linutronix.de>
The preempt_disable() section was introduced in commit
a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")
and it was said to be temporary.
fpu__initialize() initializes the FPU struct to its "init" value and
then sets ->initialized to 1. The last part is the important one.
The content of the `state' does not matter because it gets set via
copy_init_fpstate_to_fpregs().
A preemption here has little meaning because the registers will always be
set to the same content after copy_init_fpstate_to_fpregs(). A softirq
with a kernel_fpu_begin() could also force to save FPU's registers after
fpu__initialize() without changing the outcome here.
Remove the preempt_disable() section in fpu__clear(), preemption here
does not hurt.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/fpu/core.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1d3ae7988f7f2..1940319268aef 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu)
* Make sure fpstate is cleared and initialized.
*/
if (static_cpu_has(X86_FEATURE_FPU)) {
- preempt_disable();
fpu__initialize(fpu);
user_fpu_begin();
copy_init_fpstate_to_fpregs();
- preempt_enable();
}
}
--
2.20.1
next prev parent reply other threads:[~2019-03-21 20:27 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 20:26 [PATCH v8] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 01/24] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 02/24] x86/fpu: Remove fpu__restore() Sebastian Andrzej Siewior
2019-03-21 20:26 ` Sebastian Andrzej Siewior [this message]
2019-03-21 20:26 ` [PATCH 04/24] x86/fpu: Always init the `state' in fpu__clear() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 05/24] x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 06/24] x86/fpu: Don't save fxregs for ia32 frames " Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 07/24] x86/fpu: Remove fpu->initialized Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 08/24] x86/fpu: Remove user_fpu_begin() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 09/24] x86/fpu: Add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 10/24] x86/fpu: Make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 11/24] x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() " Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 12/24] x86/pkru: Provide .*_pkru_ins() functions Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 13/24] x86/fpu: Only write PKRU if it is different from current Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 14/24] x86/pkeys: Don't check if PKRU is zero before writting it Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 15/24] x86/fpu: Eager switch PKRU state Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 16/24] x86/entry: Add TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 17/24] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2019-03-31 16:54 ` Thomas Gleixner
2019-03-21 20:26 ` [PATCH 18/24] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2019-03-31 18:20 ` Thomas Gleixner
2019-04-01 8:24 ` Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 19/24] x86/fpu: Update xstate's PKRU value on write_pkru() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 20/24] x86/fpu: Inline copy_user_to_fpregs_zeroing() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 21/24] x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from kernel memory Sebastian Andrzej Siewior
2019-03-22 14:55 ` Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 22/24] x86/fpu: Merge the two code paths in __fpu__restore_sig() Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 23/24] x86/fpu: Defer FPU state load until return to userspace Sebastian Andrzej Siewior
2019-03-21 20:26 ` [PATCH 24/24] x86/pkeys: add PKRU value to init_fpstate 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=20190321202632.16810-4-bigeasy@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=Jason@zx2c4.com \
--cc=bp@suse.de \
--cc=dave.hansen@linux.intel.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=pbonzini@redhat.com \
--cc=riel@surriel.com \
--cc=rkrcmar@redhat.com \
--cc=x86@kernel.org \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).