Re: [PATCH v2 1/2] sev/i386: Introduce sev_add_kernel_loader_hashes for measured linux boot

From: Dov Murik <dovmurik@linux.ibm.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: "Tom Lendacky" <thomas.lendacky@amd.com>,
	"Ashish Kalra" <ashish.kalra@amd.com>,
	"Brijesh Singh" <brijesh.singh@amd.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Connor Kuehl" <ckuehl@redhat.com>,
	"Laszlo Ersek" <lersek@redhat.com>,
	"James Bottomley" <jejb@linux.ibm.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	qemu-devel@nongnu.org,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	dovmurik@linux.ibm.com,
	"Tobin Feldman-Fitzthum" <tobin@linux.ibm.com>,
	"Jim Cadden" <jcadden@ibm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [PATCH v2 1/2] sev/i386: Introduce sev_add_kernel_loader_hashes for measured linux boot
Date: Wed, 23 Jun 2021 12:28:31 +0300	[thread overview]
Message-ID: <4f50f4ef-b270-3985-30a7-ea5f0998d551@linux.ibm.com> (raw)
In-Reply-To: <YNL1hazUg/shU7nU@redhat.com>

On 23/06/2021 11:49, Daniel P. Berrangé wrote:
> On Wed, Jun 23, 2021 at 11:41:56AM +0300, Dov Murik wrote:

...

>>
>> Related: I wondered if I could replace HASH_SIZE in:
>>
>>
>>   /* hard code sha256 digest size */
>>   #define HASH_SIZE 32
>>
>>   typedef struct QEMU_PACKED SevHashTableEntry {
>>       QemuUUID guid;
>>       uint16_t len;
>>       uint8_t hash[HASH_SIZE];
>>   } SevHashTableEntry;
>>
>>
>> with some SHA256-related constant from crypto/hash.h, but I only found
>> the qcrypto_hash_digest_len(QCRYPTO_HASH_ALG_SHA256) function which
>> doesn't work for setting sizes of arrays at compile-time.
>>
>> Daniel: do you know what would be the proper way?
> 
> We don't have any public constants right now - they're just hardcoded
> in hash.c struct. We could define public constants, and use those in
> the struct instead, as well as in other callers.
> 

Thanks Daniel.

I see the exact same pattern in block/quorom.c (see HASH_LENGTH there).
I'll leave this change for a separate series.

-Dov