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

On 9/23/2026 8:21 AM, Jason Gunthorpe wrote:

On Wed, Sep 23, 2026 at 08:28:57PM +0530, Aneesh Kumar K.V wrote:

quoted

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?

vmbus_establish_gpadl() is the the same wrong abstraction as the arch
code. Get rid of it and use vmbus_establish_gpadl_caller_decrypted():

		pdata->recv_buf = vzalloc(RECV_BUFFER_SIZE);
		if (!pdata->recv_buf) {
			ret = -ENOMEM;
			goto fail_free_ring;
		}

		ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
					    RECV_BUFFER_SIZE, &pdata->recv_gpadl);


So you made an allocator that returns folios, now you just need to
use that allocator to implement a kvzalloc wrapper. ARM can call vmap
on decrypted memory with pgprot_decrypted(), right?

Or maybe this can use vmbus_alloc_buffer(), it already does it.

Michael Kelley recently proposed [1] moving all ring buffer allocations
to use vmbus_alloc_buffer(). If we move forward with this, it should
remove the dependency on vmalloc support.


[1] https://lore.kernel.org/all/SN6PR02MB4157B71CAC1433B04B92B700D4832@SN6PR02MB4157.namprd02.prod.outlook.com/ (local)

Kameron