On Mon, Feb 26, 2018 at 06:06:42PM +0800, Wanpeng Li wrote:
> I think it is the host admin(e.g. cloud provider)'s responsibility to
> set an expected microcode revision.
+ vcpu->arch.microcode_version = 0x1;
That already looks pretty arbitrary and non-sensical to me.
>In addition, the non-sensical value which is written by the guest will
>not reflect to guest-visible microcode revision and just be ignored in
>this implementation.
Huh? How so?
So a guest will have *two* microcode revisions - both of which are most
likely wrong?!
This whole thing sounds like the wrong approach to me.
> Linux (among the others) has checks to make sure that certain features
> aren't enabled on a certain family/model/stepping if the microcode version
> isn't greater than or equal to a known good version.
It sounds to me like the proper fix is to make the kernel *not* look at
microcode revisions when running virtualized. The same way we're not
loading microcode in a guest:
if (native_cpuid_ecx(1) & BIT(31))
Letting userspace control the microcode revision number is revision
number management SNAFU waiting to happen IMO.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
