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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
	Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] x86/spec-ctrl: Skip RSB overwriting when safe to do so
Date: Wed, 25 Aug 2021 16:11:17 +0100	[thread overview]
Message-ID: <10dabd6c-3cff-a2b1-799b-227bf39be9bd@citrix.com> (raw)
In-Reply-To: <ffb04572-eb40-64b8-2156-beac6324a5fe@suse.com>

On 25/08/2021 15:36, Jan Beulich wrote:
> On 25.08.2021 14:12, Andrew Cooper wrote:
>> On 24/08/2021 14:04, Jan Beulich wrote:
>>> On 19.08.2021 18:26, Andrew Cooper wrote:
>>>> In some configurations, it is safe to not overwrite the RSB on entry to Xen.
>>>> Both Intel and AMD have guidelines in this area, because of the performance
>>>> difference it makes for native kernels.
>>> I don't think I've come across AMD's guidelines - would you happen to
>>> have a pointer?
>> APM Vol2 3.2.9 "Speculation Control MSRs"
>>
>> The information about SMEP is in the final paragraph before describing
>> MSR_SPEC_CTRL.STIBP.
> Ah yes, thanks. Still need to get used to this now being in the PM rather
> than in one or more separate docs. I now recall reading through this.

I'm still pushing Intel to add a section/chapter to the SDM, because
this is is all architectural functionality and interfaces.

~Andrew


      reply	other threads:[~2021-08-25 15:11 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19 16:26 [PATCH] x86/spec-ctrl: Skip RSB overwriting when safe to do so Andrew Cooper
2021-08-24 13:04 ` Jan Beulich
2021-08-25 12:12   ` Andrew Cooper
2021-08-25 14:36     ` Jan Beulich
2021-08-25 15:11       ` Andrew Cooper [this message]

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