RE: [Patch v4 01/13] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute

[Michael Kelley (LINUX)]

From: Borislav Petkov <bp@xxxxxxxxx> Sent: Thursday, December 29, 2022 3:39 AM
> 
> On Tue, Dec 06, 2022 at 07:54:02PM +0000, Michael Kelley (LINUX) wrote:
> > Exactly correct.
> 
> Ok, thanks.
> 
> Let's put that in the commit message and get rid of the "subsequent
> patch" wording as patch order in git is ambiguous.
> 
> IOW, something like this:
> 
>     Current code always maps the IO-APIC as shared (decrypted) in a
>     confidential VM. But Hyper-V guest VMs on AMD SEV-SNP with vTOM enabled
>     use a paravisor running in VMPL0 to emulate the IO-APIC.
> 
>     In such a case, the IO-APIC must be accessed as private (encrypted)
>     because the paravisor emulates the IO-APIC in the lower half of the vTOM
>     where all accesses must be encrypted.
> 
>     Add a new CC attribute which determines how the IO-APIC MMIO mapping
>     should be established depending on the platform the kernel is running on
>     as a guest.
>
 
Works for me.  I'll adopt this wording in v5.

Michael