[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [xen-unstable test] 64494: regressions - FAIL
On Thu, Nov 19, 2015 at 01:29:01PM +0100, Juergen Gross wrote: [...] > > To be precise, the problem is in mini-os, which is used by rump kernel > > as well. :-( > > > >> pvgrub is making assumptions about the page table allocation scheme > >> of the toolset starting pvgrub. It is calculating the first not yet > >> mapped pfn by: > >> > >> pfn_to_map = > >> (start_info.nr_pt_frames - NOT_L1_FRAMES) * L1_PAGETABLE_ENTRIES; > >> > >> NOT_L1_FRAMES is 3 for 64 bit and 32 bit: > >> > >> 64 bit: 1 level 4 + 1 level 4 + 1 level 2 > >> 32 bit: 1 level 3 + 2 level 2 (assuming level 2 pt are allocated > >> for the first and the last GB) > >> > >> This is wrong now, as for 32 bit I'm allocating all level 2 page > >> tables from the lowest needed address up to 0xffffffff, resulting > >> in 4 level 2 page tables in pvgrub case. > >> > >> Setting NOT_L1_FRAMES to 5 for 32 bit pvgrub makes the system boot > >> again. > >> > >> I think it is wrong for pvgrub to assume a fixed allocation scheme > >> of the page tables. The question is how to fix it: either via > >> changing NOT_L1_FRAMES or by doing it in a clean but more complicated > >> way. > >> > > > > In the mean time, shall we revert the series and think about this a bit > > more? > > > > How complicated will be clean fix be? > > I think I can fix it today. I can just count the not_l1_frames > dynamically by walking through the higher level page tables. This This seems sensible. > will work for 32 and 64 bit and with and without my patch series > and even for 32 bit mini-os started via grub-xen. > > > Does changing NOT_L1_FRAMES break mini-os boot with toolstack prior to > > your series? > > Yes. > In that case I think a clean fix is required. Wei. > Juergen > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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