From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>, Fenghua Yu <fenghua.yu@intel.com>,
Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
yu-cheng yu <yu-cheng.yu@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Rik van Riel <riel@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>
Subject: [PATCH 2/5] x86/fpu: Fix FNSAVE usage in eagerfpu mode
Date: Fri, 22 Jan 2016 16:56:03 -0800 [thread overview]
Message-ID: <60662444e13c76f06e23c15c5dcdba31b4ac3d67.1453510332.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1453510332.git.luto@kernel.org>
In-Reply-To: <cover.1453510332.git.luto@kernel.org>
In eager fpu mode, having deactivated fpu without immediately
reloading some other context is illegal. Therefore, to recover from
FNSAVE, we can't just deactivate the state -- we need to reload it
if we're not actively context switching.
We had this wrong in fpu__save and fpu__copy. Fix both.
__kernel_fpu_begin was fine -- add a comment.
This fixes a warning triggerable with nofxsr eagerfpu=on.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/kernel/fpu/core.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 08e1e11a05ca..7a9244df33e2 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -114,6 +114,10 @@ void __kernel_fpu_begin(void)
kernel_fpu_disable();
if (fpu->fpregs_active) {
+ /*
+ * Ignore return value -- we don't care if reg state
+ * is clobbered.
+ */
copy_fpregs_to_fpstate(fpu);
} else {
this_cpu_write(fpu_fpregs_owner_ctx, NULL);
@@ -189,8 +193,12 @@ void fpu__save(struct fpu *fpu)
preempt_disable();
if (fpu->fpregs_active) {
- if (!copy_fpregs_to_fpstate(fpu))
- fpregs_deactivate(fpu);
+ if (!copy_fpregs_to_fpstate(fpu)) {
+ if (use_eager_fpu())
+ copy_kernel_to_fpregs(&fpu->state);
+ else
+ fpregs_deactivate(fpu);
+ }
}
preempt_enable();
}
@@ -259,7 +267,11 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
preempt_disable();
if (!copy_fpregs_to_fpstate(dst_fpu)) {
memcpy(&src_fpu->state, &dst_fpu->state, xstate_size);
- fpregs_deactivate(src_fpu);
+
+ if (use_eager_fpu())
+ copy_kernel_to_fpregs(&src_fpu->state);
+ else
+ fpregs_deactivate(src_fpu);
}
preempt_enable();
}
--
2.5.0
next prev parent reply other threads:[~2016-01-23 0:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-23 0:56 [PATCH 0/5] x86/fpu: eagerfpu fixes, speedups, and default enablement Andy Lutomirski
2016-01-23 0:56 ` [PATCH 1/5] x86/fpu: Fix math emulation in eager fpu mode Andy Lutomirski
2016-01-23 10:02 ` Borislav Petkov
2016-01-23 17:40 ` Andy Lutomirski
2016-01-23 17:51 ` Borislav Petkov
2016-01-23 0:56 ` Andy Lutomirski [this message]
2016-01-23 0:56 ` [PATCH 3/5] x86/fpu: Fold fpu_copy into fpu__copy Andy Lutomirski
2016-01-23 0:56 ` [PATCH 4/5] x86/fpu: Speed up lazy FPU restores slightly Andy Lutomirski
2016-01-23 10:14 ` Borislav Petkov
2016-01-23 22:09 ` Andy Lutomirski
2016-01-23 23:35 ` Borislav Petkov
2016-01-23 0:56 ` [PATCH 5/5] x86/fpu: Default eagerfpu=on on all CPUs Andy Lutomirski
2016-01-23 10:19 ` Borislav Petkov
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=60662444e13c76f06e23c15c5dcdba31b4ac3d67.1453510332.git.luto@kernel.org \
--to=luto@kernel.org \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=fenghua.yu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--cc=sai.praneeth.prakhya@intel.com \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
--cc=yu-cheng.yu@intel.com \
/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).