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Re: [PATCH v3 2/3] amd/msr: allow passthrough of VIRT_SPEC_CTRL for HVM guests
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 21 Apr 2022 11:39:25 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 21 Apr 2022 09:39:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 31.03.2022 11:27, Roger Pau Monne wrote:
> Allow HVM guests untrapped access to MSR_VIRT_SPEC_CTRL if the
> hardware has support for it. This requires adding logic in the
> vm{entry,exit} paths for SVM in order to context switch between the
> hypervisor value and the guest one. The added handlers for context
> switch will also be used for the legacy SSBD support.
>
> Introduce a new synthetic feature leaf (X86_FEATURE_VIRT_SC_MSR_HVM)
> to signal whether VIRT_SPEC_CTRL needs to be handled on guest
> vm{entry,exit}.
>
> This patch changes the annotation 's' to 'S' because it introduces
> support to expose VIRT_SSBD to guests by default when the host
> (virtual) hardware also supports it.
>
> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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