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Re: [PATCH for-4.17 3/4] amd/ssbd: remove hypervisor SSBD selection
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 12 Oct 2022 10:30:45 +0200
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- Cc: Henry.Wang@xxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 12 Oct 2022 08:30:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11.10.2022 18:02, Roger Pau Monne wrote:
> @@ -2365,12 +2365,6 @@ On hardware supporting STIBP (Single Thread Indirect
> Branch Predictors), the
> By default, Xen will use STIBP when IBRS is in use (IBRS implies STIBP), and
> when hardware hints recommend using it as a blanket setting.
>
> -On hardware supporting SSBD (Speculative Store Bypass Disable), the `ssbd=`
> -option can be used to force or prevent Xen using the feature itself.
Why would we want to take away this level of control? Shouldn't we turn this
on while in Xen if so requested? Which would then either mean enabling it on
VMEXIT if a guest has it off, or running with it turned on using the OR of
guest and host settings.
Jan
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