From: Aneesh Kumar K.V <aneesh.kumar@kernel.org> Sent: Thursday, June 4, 2026 7:58 AM

Michael Kelley [off-list ref] writes:

quoted

From: Jason Gunthorpe <jgg@ziepe.ca> Sent: Tuesday, June 2, 2026 5:55 PM

quoted

On Tue, Jun 02, 2026 at 02:24:40PM +0000, Michael Kelley wrote:

quoted

Except that in a normal VM, the "unencrypted" pool attribute does *not*
describe the state of the memory itself.  In a normal VM, the memory is
unencrypted, but the "unencrypted" pool attribute is false. That
contradiction is the essence of my concern.

I would argue no..

When CC is enabled the default state of memory in a Linux environment
is "encrypted". You have to take a special action to "decrypt" it.

Thus the default state of memory in a non-CC environment is also
paradoxically "encrypted" too.

The need to have such an unnatural premise is usually an indication
of a conceptual problem with the overall model, or perhaps just a
terminology problem.

Here's a proposal. The new DMA attribute is DMA_ATTR_CC_SHARED.
Name the pool attribute "cc_shared" instead of "unencrypted". Having
"cc_shared" set to false in a normal VM doesn't lead to the non-sensical
situation of claiming that a normal VM is encrypted. The boolean
"unencrypted" parameter that has been added to various calls also
becomes "cc_shared".  If "CC_SHARED" is a suitable name for the DMA
attribute, it ought to be suitable as the pool attribute. And everything
matches as well.

That is better. It would also simplify:

	if (mem->unencrypted != !!(attrs & DMA_ATTR_CC_SHARED))
		return NULL;

to
	if (mem->cc_shared != !!(attrs & DMA_ATTR_CC_SHARED))
		return NULL;


I already sent a v6 in the hope of getting this merged for the next
merge window. Should I send a v7, or would you prefer that I do the
rename on top of v6?

I would advocate for a v7 with the rename, vs. a separate follow-on
patch to do the rename, just to reduce churn. But I don't know what
the tradeoffs are in trying to hit the next merge window. If a follow-on
patch is more practical from a timing standpoint, I won't object.

Michael