Re: [PATCH 05/11] x86/snp: create snp_prepare_for_snp_init()

[Tom Lendacky <thomas.lendacky@amd.com>]

On 3/2/26 13:13, Tycho Andersen wrote:
> From: "Tycho Andersen (AMD)" <tycho@kernel.org>
> 
> In preparation for delayed SNP initialization, create a function
> snp_prepare_for_snp_init() that does the necessary architecture setup.
> Export this function for the ccp module to allow it to do the setup as
> necessary.
> 
> Also move {mfd,snp}_enable out of the __init section, since these will be
> called later.
> 
> Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>  arch/x86/include/asm/sev.h |  2 ++
>  arch/x86/virt/svm/sev.c    | 46 ++++++++++++++++++++++----------------
>  2 files changed, 29 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index 0e6c0940100f..0bcd89d4fe90 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -661,6 +661,7 @@ static inline void snp_leak_pages(u64 pfn, unsigned int pages)
>  {
>  	__snp_leak_pages(pfn, pages, true);
>  }
> +void snp_prepare_for_snp_init(void);
>  #else
>  static inline bool snp_probe_rmptable_info(void) { return false; }
>  static inline int snp_rmptable_init(void) { return -ENOSYS; }
> @@ -677,6 +678,7 @@ static inline void __snp_leak_pages(u64 pfn, unsigned int npages, bool dump_rmp)
>  static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
>  static inline void kdump_sev_callback(void) { }
>  static inline void snp_fixup_e820_tables(void) {}
> +static inline void snp_prepare_for_snp_init(void) {}
>  #endif
>  
>  #endif
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 258e67ba7415..8f50538baf7b 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 __init void mfd_enable(void *arg)
> +static void mfd_enable(void *arg)
>  {
>  	u64 val;
>  
> @@ -146,7 +146,7 @@ static __init void mfd_enable(void *arg)
>  	wrmsrq(MSR_AMD64_SYSCFG, val);
>  }
>  
> -static __init void snp_enable(void *arg)
> +static void snp_enable(void *arg)
>  {
>  	u64 val;
>  
> @@ -509,6 +509,30 @@ static bool __init setup_rmptable(void)
>  	return true;
>  }
>  
> +void snp_prepare_for_snp_init(void)
> +{
> +	u64 val;
> +
> +	/*
> +	 * Check if SEV-SNP is already enabled, this can happen in case of
> +	 * kexec boot.
> +	 */
> +	rdmsrq(MSR_AMD64_SYSCFG, val);
> +	if (val & MSR_AMD64_SYSCFG_SNP_EN)
> +		return;
> +
> +	snp_clear_rmp();
> +
> +	/*
> +	 * 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(snp_enable, NULL, 1);
> +}
> +EXPORT_SYMBOL_FOR_MODULES(snp_prepare_for_snp_init, "ccp");
> +
>  /*
>   * Do the necessary preparations which are verified by the firmware as
>   * described in the SNP_INIT_EX firmware command description in the SNP
> @@ -516,8 +540,6 @@ static bool __init setup_rmptable(void)
>   */
>  int __init snp_rmptable_init(void)
>  {
> -	u64 val;
> -
>  	if (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))
>  		return -ENOSYS;
>  
> @@ -527,22 +549,8 @@ int __init snp_rmptable_init(void)
>  	if (!setup_rmptable())
>  		return -ENOSYS;
>  
> -	/*
> -	 * Check if SEV-SNP is already enabled, this can happen in case of
> -	 * kexec boot.
> -	 */
> -	rdmsrq(MSR_AMD64_SYSCFG, val);
> -	if (val & MSR_AMD64_SYSCFG_SNP_EN)
> -		goto skip_enable;
> -
> -	snp_clear_rmp();
> -
> -	/* MtrrFixDramModEn must be enabled on all the CPUs prior to enabling SNP. */
> -	on_each_cpu(mfd_enable, NULL, 1);
> -
> -	on_each_cpu(snp_enable, NULL, 1);
> +	snp_prepare_for_snp_init();
>  
> -skip_enable:
>  	/*
>  	 * Setting crash_kexec_post_notifiers to 'true' to ensure that SNP panic
>  	 * notifier is invoked to do SNP IOMMU shutdown before kdump.