On 29/09/15 14:56, Ian Campbell wrote: > On Mon, 2015-09-28 at 21:31 +0100, Julien Grall wrote: >> When the guest is accessing the re-distributor, Xen retrieves the base >> of the re-distributor using a mask based on the stride. >> >> Although, when the stride contains multiple set, the corresponding mask > > ^bits?
I guess you mean "multiple bits set" here? > (Also, drop the "Although, "). > >> will be computed incorrectly [1] and therefore giving invalid vCPU and >> offset: >> >> (XEN) d0v0: vGICR: unknown gpa read address 000000008d130008 >> (XEN) traps.c:2447:d0v1 HSR=0x93c08006 pc=0xffffffc00032362c >> gva=0xffffff80000b0008 gpa=0x0000008d130008 >> >> For instance if the region of re-distributor is starting at 0x8d100000 >> and the stride is 0x30000, an access to the address 0x8d130008 should >> be valid and use the re-distributor of vCPU1 with an offset of 0x8. >> Although, Xen is returning the vCPU0 and an offset of 0x20008. >> >> I didn't find a way to replace the current computation of the mask with >> a valid. The only solution I have found is to pass the region in private > > ^one > >> data of the handler. So we can directly get the offset from the >> beginning of the region and find the corresponding vCPU/offset in the >> re-distributor. >> >> This is also make the code simpler and avoid fast/slow path. >> >> [1] http://lists.xen.org/archives/html/xen-devel/2015-09/msg03372.html >> >> Signed-off-by: Julien Grall <julien.gr...@citrix.com> >> >> --- >> Cc: shameerali.kolothum.th...@huawei.com >> Cc: Wei Liu <wei.l...@citrix.com> >> >> This is technically a good candidate for Xen 4.6. Without it DOM0 >> may not be able to bring secondary CPU on platform using a stride >> with multiple bit set [1]. Although, we don't support such platform >> right now. So I would rather defer this change to Xen 4.6.1 and >> avoid possible downside/bug in this patch. > > Agreed. > > Other than the text: > > Acked-by: Ian Campbell <ian.campb...@citrix.com> Thank you. Regards, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
