Re: [PATCH Part1 RFC v2 13/20] x86/sev: Register GHCB memory when SEV-SNP is active

[Brijesh Singh <brijesh.singh@amd.com>]

On 5/26/21 4:57 AM, Borislav Petkov wrote:
> On Tue, May 25, 2021 at 09:47:24AM -0500, Brijesh Singh wrote:
>> Maybe I should have said, its not applicable in the decompressed path.
> Aha, ok. How's that, ontop of yours:

Sure, its fine with me. I will apply this change.

-Birjesh


> ---
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 07b9529d7d95..c9dd98b9dcdf 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -208,7 +208,7 @@ static bool early_setup_sev_es(void)
>  
>  	/* SEV-SNP guest requires the GHCB GPA must be registered */
>  	if (sev_snp_enabled())
> -		snp_register_ghcb(__pa(&boot_ghcb_page));
> +		snp_register_ghcb_early(__pa(&boot_ghcb_page));
>  
>  	return true;
>  }
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 37a23c524f8c..7200f44d6b6b 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -81,7 +81,7 @@ static bool ghcb_get_hv_features(void)
>  	return true;
>  }
>  
> -static void snp_register_ghcb(unsigned long paddr)
> +static void snp_register_ghcb_early(unsigned long paddr)
>  {
>  	unsigned long pfn = paddr >> PAGE_SHIFT;
>  	u64 val;
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 5544557d9fb6..144c20479cae 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -108,7 +108,18 @@ DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);
>  void do_early_exception(struct pt_regs *regs, int trapnr);
>  
>  /* Defined in sev-shared.c */
> -static void snp_register_ghcb(unsigned long paddr);
> +static void snp_register_ghcb_early(unsigned long paddr);
> +
> +static void snp_register_ghcb(struct sev_es_runtime_data *data,
> +			      unsigned long paddr)
> +{
> +	if (data->snp_ghcb_registered)
> +		return;
> +
> +	snp_register_ghcb_early(paddr);
> +
> +	data->snp_ghcb_registered = true;
> +}
>  
>  static void __init setup_vc_stacks(int cpu)
>  {
> @@ -239,10 +250,8 @@ static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state)
>  	}
>  
>  	/* SEV-SNP guest requires that GHCB must be registered before using it. */
> -	if (sev_snp_active() && !data->snp_ghcb_registered) {
> -		snp_register_ghcb(__pa(ghcb));
> -		data->snp_ghcb_registered = true;
> -	}
> +	if (sev_snp_active())
> +		snp_register_ghcb(data, __pa(ghcb));
>  
>  	return ghcb;
>  }
> @@ -681,7 +690,7 @@ static bool __init sev_es_setup_ghcb(void)
>  
>  	/* SEV-SNP guest requires that GHCB GPA must be registered */
>  	if (sev_snp_active())
> -		snp_register_ghcb(__pa(&boot_ghcb_page));
> +		snp_register_ghcb_early(__pa(&boot_ghcb_page));
>  
>  	return true;
>  }
>