Re: [PATCH v3 3/7] x86/snp: create snp_x86_shutdown()

[Borislav Petkov]

On Tue, Mar 17, 2026 at 10:21:53AM -0600, Tycho Andersen wrote:
> Subject: Re: [PATCH v3 3/7] x86/snp: create snp_x86_shutdown()

"x86/sev: ..."

The tip tree preferred format for patch subject prefixes is
'subsys/component:', e.g. 'x86/apic:', 'x86/mm/fault:', 'sched/fair:',
'genirq/core:'. Please do not use file names or complete file paths as
prefix. 'git log path/to/file' should give you a reasonable hint in most
cases.

The condensed patch description in the subject line should start with a
uppercase letter and should be written in imperative tone.

Check your whole set pls.

> From: "Tycho Andersen (AMD)" <tycho@xxxxxxxxxx>
> 
> After SNP_SHUTDOWN, two architecture-level things should be done:

"architecture-level things"?

> 1. clear the RMP table
> 2. disable MFDM to prevent the FW_WARN in k8_check_syscfg_dram_mod_en() in
>    the event of a kexec
> 
> Create and export to the CCP driver a function that does them.
> 
> Also change the MFDM helper to allow for disabling the bit, since the SNP
> x86 shutdown path needs to disable MFDM. The comment for
> k8_check_syscfg_dram_mod_en() notes, the "BIOS" is supposed clear it, or
> the kernel in the case of module unload and shutdown followed by kexec.
> 
> Signed-off-by: Tycho Andersen (AMD) <tycho@xxxxxxxxxx>
> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
>  arch/x86/include/asm/sev.h |  2 ++
>  arch/x86/virt/svm/sev.c    | 23 ++++++++++++++++++++---
>  2 files changed, 22 insertions(+), 3 deletions(-)

...

> @@ -521,12 +524,26 @@ void snp_prepare_for_snp_init(void)
>  	 * MtrrFixDramModEn is not shared between threads on a core,
>  	 * therefore it must be set on all CPUs prior to enabling SNP.
>  	 */
> -	on_each_cpu(mfd_enable, NULL, 1);
> +	on_each_cpu(mfd_reconfigure, (void *)1, 1);
				     ^^^^^^^^^
ew.

>  	on_each_cpu(snp_enable, NULL, 1);
>  }
>  EXPORT_SYMBOL_FOR_MODULES(snp_prepare_for_snp_init, "ccp");
>  
> +void snp_x86_shutdown(void)

"snp" and "x86" prefixes?

> +{
> +	u64 syscfg;
> +
> +	rdmsrq(MSR_AMD64_SYSCFG, syscfg);
> +

^ Superfluous newline.

> +	if (syscfg & MSR_AMD64_SYSCFG_SNP_EN)
> +		return;
> +
> +	clear_rmp();
> +	on_each_cpu(mfd_reconfigure, 0, 1);

s/0/NULL/

> +}
> +EXPORT_SYMBOL_FOR_MODULES(snp_x86_shutdown, "ccp");
> +
>  /*
>   * Do the necessary preparations which are verified by the firmware as
>   * described in the SNP_INIT_EX firmware command description in the SNP
> -- 
> 2.53.0
> 

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette