On 8/10/21 10:51 AM, Kirill A. Shutemov wrote:

On Tue, Aug 10, 2021 at 10:36:21AM -0700, Dave Hansen wrote:

quoted

quoted

The difference is going to be substantially lower once we get it optimized
properly.

What does this mean?  Is this future work in the kernel or somewhere in
the TDX hardware/firmware which will speed things up?

Kernel has to be changed to accept memory in 2M and 1G chunks where
possible. The interface exists and described in spec, but not yet used in
guest kernel.

From a quick scan of the spec, I only see:

7.9.3. Page Acceptance by the Guest TD: TDG.MEM.PAGE.ACCEPT ... The guest
TD can accept a dynamically added 4KB page using TDG.MEM.PAGE.ACCEPT
with the page GPA as an input.

Is there some other 2M/1G page-acceptance call that I'm missing?

It would cut hypercall overhead dramatically. It makes upfront memory
accept more bearable and lowers latency of lazy memory accept. So I expect
the gap being not 20x, but like 3-5x (which is still huge).

It would be nice to be able to judge the benefits of this series based
on the final form.  I guess we'll take what we can get, though.

Either way, I'd still like to see some *actual* numbers for at least one
configuration:

	With this series applied, userspace starts to run at X seconds
	after kernel boot.  Without this series, userspace runs at Y
	seconds.