All of lore.kernel.org
 help / color / mirror / Atom feed
From: Borislav Petkov <bp@alien8.de>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Greg Kroah-Hartman <gregkh@linux-foundation.org>,
	David Woodhouse <dwmw@amazon.co.uk>, Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2 0/2] x86/cpu/AMD: Make LFENCE a serializing instruction on AMD
Date: Tue, 9 Jan 2018 00:52:01 +0100	[thread overview]
Message-ID: <20180108235201.6dezaklw57rmfugg@pd.tnic> (raw)
In-Reply-To: <20180108220912.12580.82330.stgit@tlendack-t1.amdoffice.net>

On Mon, Jan 08, 2018 at 04:09:12PM -0600, Tom Lendacky wrote:
> To aid in speculation control, the LFENCE instruction will be turned into
> a serializing instruction. There is less performance impact using LFENCE
> in this way compared to MFENCE.
> 
> With LFENCE now being a serializing instruction, it can be also used in
> rdtsc_ordered() in preference to MFENCE_RDTSC.  Since the kernel could
> be running under a hypervisor that does not allow writing to that MSR,
> it must be first verified that the write was successful before setting
> the LFENCE_RDTSC feature.
> 
> The following patches are included in this series:
> - Make LFENCE a serializing instruction on AMD
> - Use LFENCE_RDTSC in preference to MFENCE_RDTSC on AMD
> 
> This patch series is based on tip:x86/pti.
> 
> ---
> 
> Changes from v1:
> - Add a check verifying the MSR was actually updated
> - Remove the third patch that eliminates the MFENCE_RDTSC feature
>   (since the feature is still needed)
> - Adding Dan Williams to the cc since this will impact nospec_barrier(),
>   which will require an alternative_2 to add an MFENCE instruction with
>   an MFENCE_RDTSC check
> 
> Tom Lendacky (2):
>       x86/cpu/AMD: Make LFENCE a serializing instruction
>       x86/cpu/AMD: Use LFENCE_RDTSC in preference to MFENCE_RDTSC

Looks good to me.

Reviewed-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

      parent reply	other threads:[~2018-01-08 23:52 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-08 22:09 Tom Lendacky
2018-01-08 22:09 ` [PATCH v2 1/2] x86/cpu/AMD: Make LFENCE a serializing instruction Tom Lendacky
2018-01-09  0:48   ` [tip:x86/pti] " tip-bot for Tom Lendacky
2018-01-08 22:09 ` [PATCH v2 2/2] x86/cpu/AMD: Use LFENCE_RDTSC in preference to MFENCE_RDTSC Tom Lendacky
2018-01-09  0:49   ` [tip:x86/pti] " tip-bot for Tom Lendacky
2018-01-08 22:34 ` [PATCH v2 0/2] x86/cpu/AMD: Make LFENCE a serializing instruction on AMD Dan Williams
2018-01-08 23:52 ` Borislav Petkov [this message]

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=20180108235201.6dezaklw57rmfugg@pd.tnic \
    --to=bp@alien8.de \
    --cc=dan.j.williams@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=dwmw@amazon.co.uk \
    --cc=gregkh@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peterz@infradead.org \
    --cc=pjt@google.com \
    --cc=tglx@linutronix.de \
    --cc=thomas.lendacky@amd.com \
    --cc=tim.c.chen@linux.intel.com \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v2 0/2] x86/cpu/AMD: Make LFENCE a serializing instruction on AMD' \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.