Re: [PATCH v15 3/5] x86/sev: Initialize RMPOPT configuration MSRs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] x86/sev: missing X86_FEATURE_RMPOPT cleanup on probe failure
--

commit 1564212e828a7dee0758e1b6a358828053507df5
Author: Ashish Kalra <ashish.kalra@amd.com>
x86/sev: Initialize RMPOPT configuration MSRs

This commit initializes the per-CPU RMPOPT table base to enable RMP
optimizations for up to 2 TB of addressable memory. It introduces
snp_enable_rmpopt() to program the RMPOPT MSR once SNP is enabled and modifies
snp_probe_rmptable_info() to clear the RMPOPT capability if segmented RMP is
unavailable.

> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 558f7924a3f85..f458128b9864f 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
[ ... ]
> @@ -699,13 +735,21 @@ static bool probe_segmented_rmptable_info(void)
>  
>  bool snp_probe_rmptable_info(void)
>  {
> -	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP))
> +	if (cpu_feature_enabled(X86_FEATURE_SEGMENTED_RMP)) {
>  		rdmsrq(MSR_AMD64_RMP_CFG, rmp_cfg);
>  
> -	if (rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)
> -		return probe_segmented_rmptable_info();
> -	else
> -		return probe_contiguous_rmptable_info();
> +		if (rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)
> +			return probe_segmented_rmptable_info();

[Severity: Low]
If probe_segmented_rmptable_info() fails and returns false, does this early
return bypass the setup_clear_cpu_cap(X86_FEATURE_RMPOPT) cleanup below?

If the BIOS or firmware enables Segmented RMP but provides an invalid
configuration (e.g., missing RMP_BASE or out-of-bounds segment size), this
could leave the X86_FEATURE_RMPOPT CPU capability flag erroneously set.
Consequently, later initcalls might unnecessarily allocate resources for
RMPOPT, even though SEV-SNP initialization will subsequently fail.

> +	}
> +
> +	/*
> +	 * Segmented RMP is either not supported on the platform or is
> +	 * disabled by the firmware.  RMPOPT is not supported without
> +	 * segmented RMP.
> +	 */
> +	setup_clear_cpu_cap(X86_FEATURE_RMPOPT);
> +
> +	return probe_contiguous_rmptable_info();
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/cover.1789586444.git.ashish.kalra@amd.com?part=3