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

[Kameron Carr]

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:
> 
>> 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/

Kameron