Re: [PATCH] KVM: x86: Document a virtualization gap for GIF on AMD CPUs

[Bagas Sanjaya]

On Thu, Oct 30, 2025 at 10:37:57PM +0000, Yosry Ahmed wrote:
> -TBD
> +On AMD CPUs, when GIF is cleared, #DB exceptions or traps due to a breakpoint
> +register match are ignored and discarded by the CPU. The CPU relies on the VMM
> +to fully virtualize this behavior, even when vGIF is enabled for the guest
> +(i.e. vGIF=0 does not cause the CPU to drop #DBs when the guest is running).
> +KVM does not virtualize this behavior as the complexity is unjustified given
> +the rarity of the use case. One way to handle this would be for KVM to
> +intercept the #DB, temporarily disable the breakpoint, single-step over the
> +instruction, then re-enable the breakpoint.

The wording LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme@xxxxxxxxx>

-- 
An old man doll... just what I always wanted! - Clara

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