Re: [PATCH v4 1/2] sev/i386: Introduce sev_add_kernel_loader_hashes for measured linux boot

[Tom Lendacky]

On 9/30/21 12:49 AM, Dov Murik wrote:

...

> +/*
> + * Add the hashes of the linux kernel/initrd/cmdline to an encrypted guest page
> + * which is included in SEV's initial memory measurement.
> + */
> +bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
> +{
> +    uint8_t *data;
> +    SevHashTableDescriptor *area;
> +    SevHashTable *ht;
> +    uint8_t cmdline_hash[HASH_SIZE];
> +    uint8_t initrd_hash[HASH_SIZE];
> +    uint8_t kernel_hash[HASH_SIZE];
> +    uint8_t *hashp;
> +    size_t hash_len = HASH_SIZE;
> +    int aligned_len;
> +
> +    if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
> +        error_setg(errp, "SEV: kernel specified but OVMF has no hash table 
> guid");
> +        return false;
> +    }

This breaks backwards compatibility with an older OVMF image. Any older 
OVMF image with SEV support that doesn't have the hash table GUID will now 
fail to boot using -kernel/-initrd/-append, where it used to be able to 
boot before.

Is that anything we need to be concerned about?

Thanks,
Tom