On 3/2/26 13:13, Tycho Andersen wrote:
> From: "Tycho Andersen (AMD)" <tycho@kernel.org>
>
> The SNP x86 shutdown path needs to disable MFDM, since as the comment for
> k8_check_syscfg_dram_mod_en(), the "BIOS" is supposed clear it, or the
> kernel in the case of module unload and shutdown followed by kexec.
>
> Change this helper to allow for disabling it.
>
> Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
This could be squashed with the next patch, but either way:
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> arch/x86/virt/svm/sev.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 53bc0c7f2c50..cf984b8f4493 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -132,7 +132,7 @@ static unsigned long snp_nr_leaked_pages;
> #undef pr_fmt
> #define pr_fmt(fmt) "SEV-SNP: " fmt
>
> -static void mfd_enable(void *arg)
> +static void mfd_reconfigure(void *arg)
> {
> u64 val;
>
> @@ -141,7 +141,10 @@ static void mfd_enable(void *arg)
>
> rdmsrq(MSR_AMD64_SYSCFG, val);
>
> - val |= MSR_AMD64_SYSCFG_MFDM;
> + if (arg)
> + val |= MSR_AMD64_SYSCFG_MFDM;
> + else
> + val &= ~MSR_AMD64_SYSCFG_MFDM;
>
> wrmsrq(MSR_AMD64_SYSCFG, val);
> }
> @@ -532,7 +535,7 @@ 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);
>
> on_each_cpu(snp_enable, NULL, 1);
>