Re: [Qemu-devel] [PATCH] Fix phys memory client - pass guest physical address not region offset

[Michael S. Tsirkin]

On Fri, Apr 29, 2011 at 05:29:06PM +0200, Jan Kiszka wrote:
> On 2011-04-29 17:06, Michael S. Tsirkin wrote:
> > On Thu, Apr 28, 2011 at 09:15:23PM -0600, Alex Williamson wrote:
> >> When we're trying to get a newly registered phys memory client updated
> >> with the current page mappings, we end up passing the region offset
> >> (a ram_addr_t) as the start address rather than the actual guest
> >> physical memory address (target_phys_addr_t).  If your guest has less
> >> than 3.5G of memory, these are coincidentally the same thing.  If
> 
> I think this broke even with < 3.5G as phys_offset also encodes the
> memory type while region_offset does not. So everything became RAMthis
> way, no MMIO was announced.
> 
> >> there's more, the region offset for the memory above 4G starts over
> >> at 0, so the set_memory client will overwrite it's lower memory entries.
> >>
> >> Instead, keep track of the guest phsyical address as we're walking the
> >> tables and pass that to the set_memory client.
> >>
> >> Signed-off-by: Alex Williamson <address@hidden>
> > 
> > Acked-by: Michael S. Tsirkin <address@hidden>
> > 
> > Given all this, can yo tell how much time does
> > it take to hotplug a device with, say, a 40G RAM guest?
> 
> Why not collect pages of identical types and report them as one chunk
> once the type changes?

Sure, but before we bother to optimize this, is this too slow?

> Jan
> 
> -- 
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux