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

Michael Kelley (LINUX)
2022-12-29T16:02:44Z

From: Borislav Petkov <bp@alien8.de> 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