Re: [patch] x86/smpboot: Disable parallel bootup if cc_vendor != NONE

[Thomas Gleixner]

On Tue, May 30 2023 at 15:29, Kirill A. Shutemov wrote:
> On Tue, May 30, 2023 at 02:09:17PM +0200, Thomas Gleixner wrote:
>> The decision to allow parallel bringup of secondary CPUs checks
>> CC_ATTR_GUEST_STATE_ENCRYPT to detect encrypted guests. Those cannot use
>> parallel bootup because accessing the local APIC is intercepted and raises
>> a #VC or #VE, which cannot be handled at that point.
>> 
>> The check works correctly, but only for AMD encrypted guests. TDX does not
>> set that flag.
>> 
>> Check for cc_vendor != CC_VENDOR_NONE instead. That might be overbroad, but
>> definitely works for both AMD and Intel.
>
> It boots fine with TDX, but I think it is wrong. cc_get_vendor() will
> report CC_VENDOR_AMD even on bare metal if SME is enabled. I don't think
> we want it.

Right. Did not think about that.

But the same way is CC_ATTR_GUEST_MEM_ENCRYPT overbroad for AMD. Only
SEV-ES traps RDMSR if I'm understandig that maze correctly.

Thanks,

        tglx