Re: [Xen-devel] fixed location of share info page in HVM guests

[Olaf Hering <olaf@xxxxxxxxx>]

On Mon, Aug 27, Keir Fraser wrote:

> On 27/08/2012 22:32, "Olaf Hering" <olaf@xxxxxxxxx> wrote:
> 
> >>> Recently I tried to move the shared_info page in the pvops kernel during
> >>> shutdown, see "xen PVonHVM: move shared_info to MMIO before kexec"
> >>> patch. But this change was reverted because it caused reboot failures
> >>> because the actual moving of the shared page is fragile.
> >> 
> >> How was it fragile? Moving it into MMIO should just work?
> > 
> > The moving itself is not the issue, but the possible access to the page
> > during the move. Its not atomic, nor can it easily be atomic.
> 
> Why not map it into MMIO in the first place, rather than into the middle of
> RAM? Do that early during boot, and early during resume from
> save/restore/migrate (i.e., places you presumably already map the
> shared_info page, but into the middle of RAM)?

I think there is no easy way to know where the PCI device is located at
the time the shared info page is configured in the early kernel setup.

Olaf

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