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Re: [PATCH] x86: Add MMIO Stale Data arch_caps to hardware domain
- To: Jason Andryuk <jandryuk@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 18 Jul 2022 16:18:09 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 18 Jul 2022 14:18:21 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.07.2022 16:05, Jason Andryuk wrote:
> Let the hardware domain know about the hardware it is running on. This
> allows a linux Dom0 to know that it has the appropriate microcode via
> FB_CLEAR. /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
> changes from:
> "Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state
> unknown"
> to:
> "Mitigation: Clear CPU buffers; SMT Host state unknown"
>
> Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> ---
> Should calculate_host_policy()'s arch_caps mask also be updated? They
> are not identical today, but I'm don't know this code to understand why
> they differ.
I think this wants updating too, yes. I'm afraid I have to leave it to
Andrew to provide the reasons for the differences between the two.
I would further suggest to also consider adding RRSBA and BHI_NO, even
if then the title would want adjusting. And finally I'd like to ask to
add a proper Fixes: tag (or more), as it looks like the updating here
was simply forgotten when the bits were introduced. Ideally we'd have
a way for the compiler to remind us of updates being needed (or at
least be considered) here.
Jan
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