Ian Pratt
2006-Apr-26 20:00 UTC
RE: [Xen-devel] Regarding page table management changes from Xen v1to Xen v2 (and v3)
> > On 64b we could use the 1:1 mapping of all physmem that Xen has. > > Obviously that is infeasible on 32b. In fact the interface > (passing a > > virtual address) pretty much means we have to use a linear > mapping in > > both cases. > > Couldn''t we temporarily map the page table page? Not that we > would actually want to do that. Just trying to confirm my understand.Sure, but that''s expensive on 32b as map_domain_mem has to do real work (it''s cheap on 64b as we have a 1-to-1 map of machine memory). Ian _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Anthony Liguori
2006-Apr-26 23:33 UTC
Re: [Xen-devel] Regarding page table management changes from Xen v1to Xen v2 (and v3)
Ian Pratt wrote:>>> On 64b we could use the 1:1 mapping of all physmem that Xen has. >>> Obviously that is infeasible on 32b. In fact the interface >>> >> (passing a >> >>> virtual address) pretty much means we have to use a linear >>> >> mapping in >> >>> both cases. >>> >> Couldn''t we temporarily map the page table page? Not that we >> would actually want to do that. Just trying to confirm my understand. >> > > Sure, but that''s expensive on 32b as map_domain_mem has to do real work > (it''s cheap on 64b as we have a 1-to-1 map of machine memory). >Excellent, that''s just what I thought. Thanks Ian! Regards, Anthony Liguori> Ian >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2006-Apr-27 08:23 UTC
Re: [Xen-devel] Regarding page table management changes from Xen v1to Xen v2 (and v3)
On 27 Apr 2006, at 00:33, Anthony Liguori wrote:>>> Couldn''t we temporarily map the page table page? Not that we would >>> actually want to do that. Just trying to confirm my understand. >>> >> >> Sure, but that''s expensive on 32b as map_domain_mem has to do real >> work >> (it''s cheap on 64b as we have a 1-to-1 map of machine memory). >> > > Excellent, that''s just what I thought. > > Thanks Ian!Where do you get the machine address of the page to map, given a linear address at the hypercall interface? You''d still need a linear mapping access, but you''d want to read out the pde not the pte. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel