Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

[Dave Hansen]

On 2/23/23 12:26, Dave Hansen wrote:
>> +       if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
>> +               /*
>> +               * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
>> +               * bits, just like normal ioremap():
>> +               */
>> +               if (x86_platform.hyper.is_private_mmio(phys))
>> +                       flags = pgprot_encrypted(flags);
>> +               else
>> +                       flags = pgprot_decrypted(flags);
>> +       }
...
> It does seem a bit odd that there's a new CC_ATTR_GUEST_MEM_ENCRYPT
> check wrapping this whole thing.  I guess the trip through
> pgprot_decrypted() is harmless on normal platforms, though.

Yeah, that's _really_ odd.  Sean, were you trying to optimize away the
indirect call or something?

I would just expect the Hyper-V/vTOM code to leave
x86_platform.hyper.is_private_mmio alone unless
it *knows* the platform has private MMIO *and* CC_ATTR_GUEST_MEM_ENCRYPT.

Is there ever a case where CC_ATTR_GUEST_MEM_ENCRYPT==0 and he
Hyper-V/vTOM code would need to set x86_platform.hyper.is_private_mmio?