From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <andi@firstfloor.org>, x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 5/7] x86: Make old K8 swapgs workaround conditional
Date: Tue, 29 Apr 2014 21:57:23 -0700 [thread overview]
Message-ID: <536082B3.5010208@zytor.com> (raw)
In-Reply-To: <1398723161-21968-6-git-send-email-andi@firstfloor.org>
On 04/28/2014 03:12 PM, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> Every gs selector/index reload always paid an extra MFENCE
> between the two SWAPGS. This was to work around an old
> bug in early K8 steppings. All other CPUs don't need the extra
> mfence. Patch the extra MFENCE only in for K8.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> arch/x86/include/asm/cpufeature.h | 1 +
> arch/x86/kernel/cpu/amd.c | 3 +++
> arch/x86/kernel/entry_64.S | 10 +++++++++-
> 3 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
> index 89270b4..eb4bb46 100644
> --- a/arch/x86/include/asm/cpufeature.h
> +++ b/arch/x86/include/asm/cpufeature.h
> @@ -102,6 +102,7 @@
> #define X86_FEATURE_APERFMPERF (3*32+28) /* APERFMPERF */
> #define X86_FEATURE_EAGER_FPU (3*32+29) /* "eagerfpu" Non lazy FPU restore */
> #define X86_FEATURE_NONSTOP_TSC_S3 (3*32+30) /* TSC doesn't stop in S3 state */
> +#define X86_FEATURE_SWAPGS_MFENCE (3*32+31) /* SWAPGS may need MFENCE */
>
Nitpick: should be an X86_BUG_ instead.
-hpa
next prev parent reply other threads:[~2014-04-30 4:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-28 22:12 Add support for RD/WR FS/GSBASE Andi Kleen
2014-04-28 22:12 ` [PATCH 1/7] percpu: Add a DEFINE_PER_CPU_2PAGE_ALIGNED Andi Kleen
2014-05-02 15:18 ` Tejun Heo
2014-04-28 22:12 ` [PATCH 2/7] x86: Naturally align the debug IST stack Andi Kleen
2014-04-28 22:12 ` [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base instructions Andi Kleen
2014-04-29 14:10 ` Konrad Rzeszutek Wilk
2014-04-28 22:12 ` [PATCH 4/7] x86: Add support for rd/wr fs/gs base Andi Kleen
2014-04-29 18:19 ` Andy Lutomirski
2014-04-29 23:39 ` Andi Kleen
2014-04-30 4:52 ` H. Peter Anvin
2014-04-30 4:57 ` H. Peter Anvin
2014-04-30 23:44 ` Andy Lutomirski
2014-04-30 23:47 ` Andy Lutomirski
2014-05-01 21:15 ` Andi Kleen
2014-05-01 21:39 ` Andy Lutomirski
2014-05-01 21:51 ` Andi Kleen
2014-05-01 21:53 ` Andy Lutomirski
2014-05-01 21:58 ` H. Peter Anvin
2014-05-01 22:06 ` Andy Lutomirski
2014-05-01 22:18 ` Andi Kleen
2014-05-01 22:45 ` H. Peter Anvin
2014-04-28 22:12 ` [PATCH 5/7] x86: Make old K8 swapgs workaround conditional Andi Kleen
2014-04-30 4:57 ` H. Peter Anvin [this message]
2014-04-28 22:12 ` [PATCH 6/7] x86: Enumerate kernel FSGS capability in AT_HWCAP2 Andi Kleen
2014-04-28 22:12 ` [PATCH 7/7] x86: Add documentation for rd/wr fs/gs base Andi Kleen
2014-04-29 2:23 ` Randy Dunlap
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