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Re: [PATCH] x86/amd: Fix DE_CFG truncation in amd_check_zenbleed()
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 31 Jul 2023 11:02:33 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 31 Jul 2023 09:02:43 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 28.07.2023 20:17, Andrew Cooper wrote:
> This line:
>
> val &= ~chickenbit;
>
> ends up truncating val to 32 bits, and turning off various errata workarounds
> in Zen2 systems.
>
> Fixes: f91c5ea97067 ("x86/amd: Mitigations for Zenbleed")
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
>
> The choice is between int or uint64_t. This is one case where the insistence
> on using unsigned int as a default data type is genuinely unsafe.
It is not. The (unsigned) type should have been wide enough. From a Misra
perspective I'm pretty sure we would be better off using uint64_t. But in
the interest of getting this in without a lot of discussion I'll leave the
decision up to you; either way
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Jan
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