Re: [PATCH Part1 RFC v3 05/22] x86/sev: Add support for hypervisor feature VMGEXIT

Brijesh Singh
2021-06-07T14:58:37Z

On 6/7/21 9:19 AM, Borislav Petkov wrote:
> On Wed, Jun 02, 2021 at 09:03:59AM -0500, Brijesh Singh wrote:
>> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
>> index 70f181f20d92..94957c5bdb51 100644
>> --- a/arch/x86/kernel/sev-shared.c
>> +++ b/arch/x86/kernel/sev-shared.c
> I'm guessing this is in sev-shared.c because it is going to be used by
> both stages?

Yes,  the function is used by both the stages.

>> @@ -20,6 +20,7 @@
>> * out when the .bss section is later cleared.
>> */
>> static u16 ghcb_version __section(".data");
> State what this is:
>
> /* Bitmap of SEV features supported by the hypervisor */

Noted.

>
>> +static u64 hv_features __section(".data");
> Also, I'm assuming that bitmap remains immutable during the guest
> lifetime so you can do:
>
> static u64 hv_features __ro_after_init;
>
> instead, which will do:
>
> static u64 hv_features __attribute__((__section__(".data..ro_after_init")));
>
> and it'll be in the data section and then also marked read-only after
> init, after mark_rodata_ro() more specifically.

Yes, it should be immutable. I will set the ro_after_init section to
mark it read-only. thanks