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Date:   Wed, 25 Aug 2021 12:14:48 -0500
From:   Michael Roth <michael.roth@amd.com>
To:     Borislav Petkov <bp@alien8.de>
Cc:     Brijesh Singh <brijesh.singh@amd.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
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        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>,
        Wanpeng Li <wanpengli@tencent.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>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>, tony.luck@intel.com,
        marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH Part1 v5 26/38] x86/compressed/acpi: move EFI config
 table access to common code
Message-ID: <20210825171448.zaakoue7ilbmsrau@amd.com>
References: <20210820151933.22401-1-brijesh.singh@amd.com>
 <20210820151933.22401-27-brijesh.singh@amd.com>
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On Wed, Aug 25, 2021 at 05:18:20PM +0200, Borislav Petkov wrote:
> On Fri, Aug 20, 2021 at 10:19:21AM -0500, 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. 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>
> > ---
> >  arch/x86/boot/compressed/Makefile |   1 +
> >  arch/x86/boot/compressed/acpi.c   | 113 +++++--------------
> >  arch/x86/boot/compressed/efi.c    | 178 ++++++++++++++++++++++++++++++
> >  arch/x86/boot/compressed/misc.h   |  43 ++++++++
> >  4 files changed, 251 insertions(+), 84 deletions(-)
> >  create mode 100644 arch/x86/boot/compressed/efi.c
> 
> Ok, better, but this patch needs splitting. And I have a good idea how:
> in at least three patches:
> 
> 1. Add efi_get_system_table() and use it
> 2. Add efi_get_conf_table() and use it
> 3. Add efi_find_vendor_table() and use it
> 
> This will facilitate review immensely.

Ok, that makes sense.

> 
> Also, here's a diff ontop of what to do also, style-wise.
> 
> - change how you look for the preferred vendor table along with commenting what you do
> - shorten variable names so that you don't have so many line breaks.

Thanks for the suggestions, I'll incorporate those changes in the next spin as
well.

> 
> Thx.
> 
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index 3a3f997d7210..c22b21e94a95 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -20,27 +20,29 @@
>   */
>  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_table_pa,
> -		    unsigned int config_table_len, 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 ret;
>  
> -	ret = efi_find_vendor_table(config_table_pa, config_table_len,
> -				    ACPI_20_TABLE_GUID, efi_64,
> -				    (unsigned long *)&rsdp_addr);
> -	if (ret == -ENOENT)
> -		ret = efi_find_vendor_table(config_table_pa, config_table_len,
> -					    ACPI_TABLE_GUID, efi_64,
> -					    (unsigned long *)&rsdp_addr);
> +	/*
> +	 * 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;
>  }
> @@ -100,18 +102,16 @@ static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
>  static acpi_physical_address efi_get_rsdp_addr(void)
>  {
>  #ifdef CONFIG_EFI
> -	unsigned long config_table_pa = 0;
> -	unsigned int config_table_len;
> +	unsigned long cfg_tbl_pa = 0;
> +	unsigned int cfg_tbl_len;
>  	bool efi_64;
>  	int ret;
>  
> -	ret = efi_get_conf_table(boot_params, &config_table_pa,
> -				 &config_table_len, &efi_64);
> -	if (ret || !config_table_pa)
> +	ret = efi_get_conf_table(boot_params, &cfg_tbl_pa, &cfg_tbl_len, &efi_64);
> +	if (ret || !cfg_tbl_pa)
>  		error("EFI config table not found.");
>  
> -	return __efi_get_rsdp_addr(config_table_pa, config_table_len,
> -				   efi_64);
> +	return __efi_get_rsdp_addr(cfg_tbl_pa, cfg_tbl_len, efi_64);
>  #else
>  	return 0;
>  #endif
> diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
> index 16ff5cb9a1fb..7ed31b943c04 100644
> --- a/arch/x86/boot/compressed/efi.c
> +++ b/arch/x86/boot/compressed/efi.c
> @@ -12,14 +12,14 @@
>  #include <asm/efi.h>
>  
>  /* Get vendor table address/guid from EFI config table at the given index */
> -static int get_vendor_table(void *conf_table, unsigned int idx,
> +static int get_vendor_table(void *cfg_tbl, unsigned int idx,
>  			    unsigned long *vendor_table_pa,
>  			    efi_guid_t *vendor_table_guid,
>  			    bool efi_64)
>  {
>  	if (efi_64) {
>  		efi_config_table_64_t *table_entry =
> -			(efi_config_table_64_t *)conf_table + idx;
> +			(efi_config_table_64_t *)cfg_tbl + idx;
>  
>  		if (!IS_ENABLED(CONFIG_X86_64) &&
>  		    table_entry->table >> 32) {
> @@ -32,7 +32,7 @@ static int get_vendor_table(void *conf_table, unsigned int idx,
>  
>  	} else {
>  		efi_config_table_32_t *table_entry =
> -			(efi_config_table_32_t *)conf_table + idx;
> +			(efi_config_table_32_t *)cfg_tbl + idx;
>  
>  		*vendor_table_pa = table_entry->table;
>  		*vendor_table_guid = table_entry->guid;
> @@ -45,27 +45,25 @@ static int get_vendor_table(void *conf_table, unsigned int idx,
>   * Given EFI config table, search it for the physical address of the vendor
>   * table associated with GUID.
>   *
> - * @conf_table:        pointer to EFI configuration table
> - * @conf_table_len:    number of entries in EFI configuration table
> + * @cfg_tbl:        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_table_pa:   location to store physical address of vendor table
>   *
>   * Returns 0 on success. On error, return params are left unchanged.
>   */
> -int
> -efi_find_vendor_table(unsigned long conf_table_pa, unsigned int conf_table_len,
> -		      efi_guid_t guid, bool efi_64,
> -		      unsigned long *vendor_table_pa)
> +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_table_pa)
>  {
>  	unsigned int i;
>  
> -	for (i = 0; i < conf_table_len; i++) {
> +	for (i = 0; i < cfg_tbl_len; i++) {
>  		unsigned long vendor_table_pa_tmp;
>  		efi_guid_t vendor_table_guid;
>  		int ret;
>  
> -		if (get_vendor_table((void *)conf_table_pa, i,
> +		if (get_vendor_table((void *)cfg_tbl_pa, i,
>  				     &vendor_table_pa_tmp,
>  				     &vendor_table_guid, efi_64))
>  			return -EINVAL;
> @@ -88,9 +86,8 @@ efi_find_vendor_table(unsigned long conf_table_pa, unsigned int conf_table_len,
>   *
>   * Returns 0 on success. On error, return params are left unchanged.
>   */
> -int
> -efi_get_system_table(struct boot_params *boot_params,
> -		     unsigned long *sys_table_pa, bool *is_efi_64)
> +int efi_get_system_table(struct boot_params *boot_params, unsigned long *sys_table_pa,
> +			 bool *is_efi_64)
>  {
>  	unsigned long sys_table;
>  	struct efi_info *ei;
> @@ -137,22 +134,19 @@ efi_get_system_table(struct boot_params *boot_params,
>   * address EFI configuration table.
>   *
>   * @boot_params:        pointer to boot_params
> - * @conf_table_pa:      location to store physical address of config table
> - * @conf_table_len:     location to store number of config table entries
> + * @cfg_tbl_pa:      location to store physical address of config table
> + * @cfg_tbl_len:     location to store number of config table entries
>   * @is_efi_64:          location to store whether using 64-bit EFI or not
>   *
>   * Returns 0 on success. On error, return params are left unchanged.
>   */
> -int
> -efi_get_conf_table(struct boot_params *boot_params,
> -		   unsigned long *conf_table_pa,
> -		   unsigned int *conf_table_len,
> -		   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)
>  {
>  	unsigned long sys_table_pa = 0;
>  	int ret;
>  
> -	if (!conf_table_pa || !conf_table_len || !is_efi_64)
> +	if (!cfg_tbl_pa || !cfg_tbl_len || !is_efi_64)
>  		return -EINVAL;
>  
>  	ret = efi_get_system_table(boot_params, &sys_table_pa, is_efi_64);
> @@ -164,14 +158,14 @@ efi_get_conf_table(struct boot_params *boot_params,
>  		efi_system_table_64_t *stbl =
>  			(efi_system_table_64_t *)sys_table_pa;
>  
> -		*conf_table_pa	= stbl->tables;
> -		*conf_table_len	= stbl->nr_tables;
> +		*cfg_tbl_pa	= stbl->tables;
> +		*cfg_tbl_len	= stbl->nr_tables;
>  	} else {
>  		efi_system_table_32_t *stbl =
>  			(efi_system_table_32_t *)sys_table_pa;
>  
> -		*conf_table_pa	= stbl->tables;
> -		*conf_table_len	= stbl->nr_tables;
> +		*cfg_tbl_pa	= stbl->tables;
> +		*cfg_tbl_len	= stbl->nr_tables;
>  	}
>  
>  	return 0;
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
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