Re: [PATCH v3 2/6] x86/sev: Add support for enabling RMPOPT

[Dave Hansen]

On 3/30/26 15:26, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
> 
> The new RMPOPT instruction helps manage per-CPU RMP optimization
> structures inside the CPU. It takes a 1GB-aligned physical address
> and either returns the status of the optimizations or tries to enable
> the optimizations.
> 
> Per-CPU RMPOPT tables support at most 2 TB of addressable memory for
> RMP optimizations.
> 
> Initialize the per-CPU RMPOPT table base to the starting physical
> address. This enables RMP optimization for up to 2 TB of system RAM on
> all CPUs.

Isn't the Subject: more appropriately something like:

	x86/sev: Initialize RMPOPT configuration MSRs
The subject is too generic as-is.

> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index be3e3cc963b2..9c8a6dfd7891 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -758,6 +758,9 @@
>  #define MSR_AMD64_SEG_RMP_ENABLED_BIT	0
>  #define MSR_AMD64_SEG_RMP_ENABLED	BIT_ULL(MSR_AMD64_SEG_RMP_ENABLED_BIT)
>  #define MSR_AMD64_RMP_SEGMENT_SHIFT(x)	(((x) & GENMASK_ULL(13, 8)) >> 8)
> +#define MSR_AMD64_RMPOPT_BASE		0xc0010139
> +#define MSR_AMD64_RMPOPT_ENABLE_BIT	0
> +#define MSR_AMD64_RMPOPT_ENABLE		BIT_ULL(MSR_AMD64_RMPOPT_ENABLE_BIT)
>  
>  #define MSR_SVSM_CAA			0xc001f000
>  
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index e35fac0a8a3d..dc6a8e102cdc 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -477,6 +477,30 @@ static bool __init setup_rmptable(void)
>  	return true;
>  }
>  
> +static __init void configure_and_enable_rmpopt(void)
> +{

Nit: just "setup_rmpopt()" would be fine, IMNHO. We have plenty of
"setup_foo()" functions that configure and enable CPU features.

> +	phys_addr_t pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);
> +	u64 rmpopt_base = pa_start | MSR_AMD64_RMPOPT_ENABLE;
> +	int cpu;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_RMPOPT))
> +		return;
> +
> +	if (!(rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)) {
> +		pr_notice("RMPOPT optimizations not enabled, segmented RMP required\n");
> +		return;
> +	}
> +
> +	/*
> +	 * Per-CPU RMPOPT tables support at most 2 TB of addressable memory
> +	 * for RMP optimizations. Initialize the per-CPU RMPOPT table base
> +	 * to the starting physical address to enable RMP optimizations for
> +	 * up to 2 TB of system RAM on all CPUs.
> +	 */
> +	for_each_online_cpu(cpu)
> +		wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, rmpopt_base);
> +}
> +

With those nits fixed:

Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>