Date:   Thu, 6 Jan 2022 14:47:52 -0600
From:   Venu Busireddy <venu.busireddy@oracle.com>
To:     Brijesh Singh <brijesh.singh@amd.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Borislav Petkov <bp@alien8.de>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v8 26/40] x86/compressed/acpi: move EFI vendor table
 lookup to helper
Message-ID: <YddVeKgHAaB4A1Cd@dt>
References: <20211210154332.11526-1-brijesh.singh@amd.com>
 <20211210154332.11526-27-brijesh.singh@amd.com>
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On 2021-12-10 09:43:18 -0600, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@amd.com>
> 
> Future patches for SEV-SNP-validated CPUID will also require early
> parsing of the EFI configuration. Incrementally move the related code
> into a set of helpers that can be re-used for that purpose.
> 
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>

> ---
>  arch/x86/boot/compressed/acpi.c | 50 ++++++++-----------------
>  arch/x86/boot/compressed/efi.c  | 65 +++++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/misc.h |  9 +++++
>  3 files changed, 90 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index fea72a1504ff..0670c8f8888a 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -20,46 +20,28 @@
>   */
>  struct mem_vector immovable_mem[MAX_NUMNODES*2];
>  
> -/*
> - * Search EFI system tables for RSDP.  If both ACPI_20_TABLE_GUID and
> - * ACPI_TABLE_GUID are found, take the former, which has more features.
> - */
>  static acpi_physical_address
> -__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
> -		    bool efi_64)
> +__efi_get_rsdp_addr(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len, bool efi_64)
>  {
>  	acpi_physical_address rsdp_addr = 0;
>  
>  #ifdef CONFIG_EFI
> -	int i;
> -
> -	/* Get EFI tables from systab. */
> -	for (i = 0; i < nr_tables; i++) {
> -		acpi_physical_address table;
> -		efi_guid_t guid;
> -
> -		if (efi_64) {
> -			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables + i;
> -
> -			guid  = tbl->guid;
> -			table = tbl->table;
> -
> -			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
> -				debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
> -				return 0;
> -			}
> -		} else {
> -			efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables + i;
> -
> -			guid  = tbl->guid;
> -			table = tbl->table;
> -		}
> +	int ret;
>  
> -		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> -			rsdp_addr = table;
> -		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> -			return table;
> -	}
> +	/*
> +	 * Search EFI system tables for RSDP. Preferred is ACPI_20_TABLE_GUID to
> +	 * ACPI_TABLE_GUID because it has more features.
> +	 */
> +	ret = efi_find_vendor_table(cfg_tbl_pa, cfg_tbl_len, ACPI_20_TABLE_GUID,
> +				    efi_64, (unsigned long *)&rsdp_addr);
> +	if (!ret)
> +		return rsdp_addr;
> +
> +	/* No ACPI_20_TABLE_GUID found, fallback to ACPI_TABLE_GUID. */
> +	ret = efi_find_vendor_table(cfg_tbl_pa, cfg_tbl_len, ACPI_TABLE_GUID,
> +				    efi_64, (unsigned long *)&rsdp_addr);
> +	if (ret)
> +		debug_putstr("Error getting RSDP address.\n");
>  #endif
>  	return rsdp_addr;
>  }
> diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
> index 08ad517b0731..c1ddc72ef4d9 100644
> --- a/arch/x86/boot/compressed/efi.c
> +++ b/arch/x86/boot/compressed/efi.c
> @@ -112,3 +112,68 @@ int efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_p
>  
>  	return 0;
>  }
> +
> +/* Get vendor table address/guid from EFI config table at the given index */
> +static int get_vendor_table(void *cfg_tbl, unsigned int idx,
> +			    unsigned long *vendor_tbl_pa,
> +			    efi_guid_t *vendor_tbl_guid,
> +			    bool efi_64)
> +{
> +	if (efi_64) {
> +		efi_config_table_64_t *tbl_entry =
> +			(efi_config_table_64_t *)cfg_tbl + idx;
> +
> +		if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) {
> +			debug_putstr("Error: EFI config table entry located above 4GB.\n");
> +			return -EINVAL;
> +		}
> +
> +		*vendor_tbl_pa		= tbl_entry->table;
> +		*vendor_tbl_guid	= tbl_entry->guid;
> +
> +	} else {
> +		efi_config_table_32_t *tbl_entry =
> +			(efi_config_table_32_t *)cfg_tbl + idx;
> +
> +		*vendor_tbl_pa		= tbl_entry->table;
> +		*vendor_tbl_guid	= tbl_entry->guid;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * efi_find_vendor_table - Given EFI config table, search it for the physical
> + *                         address of the vendor table associated with GUID.
> + *
> + * @cfg_tbl_pa:        pointer to EFI configuration table
> + * @cfg_tbl_len:       number of entries in EFI configuration table
> + * @guid:              GUID of vendor table
> + * @efi_64:            true if using 64-bit EFI
> + * @vendor_tbl_pa:     location to store physical address of vendor table
> + *
> + * Return: 0 on success. On error, return params are left unchanged.
> + */
> +int efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
> +			  efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < cfg_tbl_len; i++) {
> +		unsigned long vendor_tbl_pa_tmp;
> +		efi_guid_t vendor_tbl_guid;
> +		int ret;
> +
> +		if (get_vendor_table((void *)cfg_tbl_pa, i,
> +				     &vendor_tbl_pa_tmp,
> +				     &vendor_tbl_guid, efi_64))
> +			return -EINVAL;
> +
> +		if (!efi_guidcmp(guid, vendor_tbl_guid)) {
> +			*vendor_tbl_pa = vendor_tbl_pa_tmp;
> +			return 0;
> +		}
> +	}
> +
> +	return -ENOENT;
> +}
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index 1c69592e83da..e9fde1482fbe 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -183,6 +183,8 @@ int efi_get_system_table(struct boot_params *boot_params,
>  			 unsigned long *sys_tbl_pa, bool *is_efi_64);
>  int efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
>  		       unsigned int *cfg_tbl_len, bool *is_efi_64);
> +int efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
> +			  efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa);
>  #else
>  static inline int
>  efi_get_system_table(struct boot_params *boot_params,
> @@ -197,6 +199,13 @@ efi_get_conf_table(struct boot_params *boot_params, unsigned long *cfg_tbl_pa,
>  {
>  	return -ENOENT;
>  }
> +
> +static inline int
> +efi_find_vendor_table(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len,
> +		      efi_guid_t guid, bool efi_64, unsigned long *vendor_tbl_pa)
> +{
> +	return -ENOENT;
> +}
>  #endif /* CONFIG_EFI */
>  
>  #endif /* BOOT_COMPRESSED_MISC_H */
> -- 
> 2.25.1
>