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Re: [PATCH v2 for-4.15] x86/msr: introduce an option for HVM relaxed rdmsr behavior
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Thu, 4 Mar 2021 18:09:58 -0500
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- Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
- Delivery-date: Thu, 04 Mar 2021 23:10:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 3/4/21 9:47 AM, Roger Pau Monne wrote:
> Introduce an option to allow selecting a less strict behaviour for
> rdmsr accesses targeting a MSR not explicitly handled by Xen. Since
> commit 84e848fd7a162f669 accesses to MSRs not explicitly handled by
> Xen result in the injection of a #GP to the guest. This is a behavior
> change since previously a #GP was only injected if accessing the MSR
> on the real hardware will also trigger a #GP.
>
> This commit attempts to offer a fallback option similar to the
> previous behavior. Note however that the value of the underlying MSR
> is never leaked to the guest, as the newly introduced option only
> changes whether a #GP is injected or not.
>
> Long term the plan is to properly handle all the MSRs, so the option
> introduced here should be considered a temporary resort for OSes that
> don't work properly with the new MSR policy. Any OS that requires this
> option to be enabled should be reported to
> xen-devel@xxxxxxxxxxxxxxxxxxxx.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Changes since v1:
> - Only apply the option to HVM guests.
> - Only apply the special handling to MSR reads.
> - Sanitize the newly introduced flags field.
> - Print a warning message when the option is used.
> ---
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> Boris, could you please test with Solaris to see if this fixes the
> issue?
Yes, still works. (It worked especially well after I noticed new option name
;-))
-boris
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