Hi Stefano,
On 24/05/2024 23:49, Stefano Stabellini wrote:
On Fri, 24 May 2024, Julien Grall wrote:
Hi Henry,
+ Juergen as the Xenstore maintainers. I'd like his opinion on the approach.
The documentation of the new logic is in:
https://lore.kernel.org/xen-devel/20240517032156.1490515-5-xin.wa...@amd.com/
FWIW I am happy in principle with the logic (this is what we discussed on the
call last week). Some comments below.
On 17/05/2024 04:21, Henry Wang wrote:
There are use cases (for example using the PV driver) in Dom0less
setup that require Dom0less DomUs start immediately with Dom0, but
initialize XenStore later after Dom0's successful boot and call to
the init-dom0less application.
An error message can seen from the init-dom0less application on
1:1 direct-mapped domains:
```
Allocating magic pages
memory.c:238:d0v0 mfn 0x39000 doesn't belong to d1
Error on alloc magic pages
```
The "magic page" is a terminology used in the toolstack as reserved
pages for the VM to have access to virtual platform capabilities.
Currently the magic pages for Dom0less DomUs are populated by the
init-dom0less app through populate_physmap(), and populate_physmap()
automatically assumes gfn == mfn for 1:1 direct mapped domains. This
cannot be true for the magic pages that are allocated later from the
init-dom0less application executed in Dom0. For domain using statically
allocated memory but not 1:1 direct-mapped, similar error "failed to
retrieve a reserved page" can be seen as the reserved memory list is
empty at that time.
Since for init-dom0less, the magic page region is only for XenStore.
To solve above issue, this commit allocates the XenStore page for
Dom0less DomUs at the domain construction time. The PFN will be
noted and communicated to the init-dom0less application executed
from Dom0. To keep the XenStore late init protocol, set the connection
status to XENSTORE_RECONNECT.
So this commit is allocating the page, but it will not be used by
init-dom0less until the next patch. But Linux could use it. So would this
break bisection? If so, then I think patch #3 needs to be folded in this
patch.
I think that's fine,
I am not sure what you mean. Are you saying it is ok to break bisection?
I'll leave that with you on commit.
I am sorry but I don't think the folding should be done on commit. It
should happen before hand because the commit message will also need to
be updated.
Cheers,
--
Julien Grall
