Re: [RFC PATCH v7 02/13] mm: Add an allocator for CoCo shared memory

[Aneesh Kumar K.V <aneesh.kumar@kernel.org>]

Jason Gunthorpe <jgg@ziepe.ca> writes:

> On Wed, Sep 23, 2026 at 11:40:36AM +0100, Catalin Marinas wrote:
>
>> The simplest is probably to always zero in the backend and ignore
>> __GFP_ZERO to the allocator. But it's probably only marginally smaller
>> than passing a CC_SHARED_ZERO flag down. Get codex to try this as well
>> and compare the diffstat.
>
> For patch ordering I would convert to use the allocator first
>
> The semantics of the new API should be clear
>
> If you pass GFP_ZERO then the resulting allocated memory is zero
>
> Otherwise the allocator does Whatever The Arch Needs to not leak
> private data out.
>

ok

>
> Once places are converted to the allocator lets go see what is left
> and ask why it is left and what API it actually needs.
>

I'm also considering requiring the address passed to cc_make_shared() to
be in the linear map. This is currently required by both TDX and CCA,
while AMD SNP appears to support vmalloc addresses. The only user of
that vmalloc support is Hyper-V VMBus GPADL setup
(vmbus_establish_gpadl()). How should the generic CoCo shared-memory
allocator handle this?

-aneesh