[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH] stubdom: foreignmemory: Fix build after 0dbb4be739c5

On 13/07/2021 15:23, Jan Beulich wrote:
On 13.07.2021 16:19, Julien Grall wrote:
On 13/07/2021 15:14, Jan Beulich wrote:
And I don't think it should be named XC_PAGE_*, but rather XEN_PAGE_*.

Even that doesn't seem right to me, at least in principle. There shouldn't
be a build time setting when it may vary at runtime. IOW on Arm I think a
runtime query to the hypervisor would be needed instead.

Yes, we want to be able to use the same userspace/OS without rebuilding
to a specific hypervisor page size.

And thinking
even more generally, perhaps there could also be mixed (base) page sizes
in use at run time, so it may need to be a bit mask which gets returned.

I am not sure to understand this. Are you saying the hypervisor may use
at the same time different page size?

I think so, yes. And I further think the hypervisor could even allow its
guests to do so.

This is already the case on Arm. We need to differentiate between the page size used by the guest and the one used by Xen for the stage-2 page table (what you call EPT on x86).

In this case, we are talking about the page size used by the hypervisor to configure the stage-2 page table

There would be a distinction between the granularity at
which RAM gets allocated and the granularity at which page mappings (RAM
or other) can be established. Which yields an environment which I'd say
has no clear "system page size".

I don't quite understand why you would allocate and etablish the memory with a different page size in the hypervisor. Can you give an example?


Julien Grall



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.