Hi All, I am sorry for the delay. I was away for my Diwali holidays and came back to office today. On Tue, Nov 6, 2018 at 2:14 PM Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > On 6 November 2018 at 02:30, Will Deacon <will.deacon@xxxxxxx> wrote: > > On Fri, Nov 02, 2018 at 02:44:10AM +0530, Bhupesh Sharma wrote: > >> With the latest EFI changes for memblock reservation across kdump > >> kernel from Ard (Commit 71e0940d52e107748b270213a01d3b1546657d74 > >> ["efi: honour memory reservations passed via a linux specific config > >> table"]), we hit a panic while trying to boot the kdump kernel on > >> machines which have large number of CPUs. > >> > >> I have a arm64 board which has 224 CPUS: > >> # lscpu > >> <..snip..> > >> CPU(s): 224 > >> On-line CPU(s) list: 0-223 > >> <..snip..> > >> > >> Here are the crash logs in the kdump kernel on this machine: > >> > >> [ 0.000000] Unable to handle kernel paging request at virtual > >> address ffff80003ffe0000 > >> val____)nt EL), IL ata abort info: > >> [ 0.or: Oops: 960000inted 4.18.0+ #3 > >> [ 0.000000] pstate: 20400089 (nzCv daIf +PAN -UAO) > >> [ 0.000000] pc : __memcpy+0x110/0x180 > >> [ 0.000000] lr : memblock_double_array+0x240/0x348 > >> [ 0.000000] sp : ffff0000092efc80 x28: 00000000bffe0000 > >> [ 0.000000] x27: 0000000000001800 x26: ffff000009d59000 > >> [ 0.000000] x25: ffff80003ffe0000 x24: 0000000000000000 > >> [ 0.000000] x23: 0000000000010000 x22: ffff000009d594e8 > >> [ 0.000000] x21: ffff000009d594f4 x20: ffff0000093c7268 > >> [ 0.000000] x19: 0000000000000c00 x18: 0000000000000010 > >> [ 0.000000] x17: 0000000000000000 x16: 0000000000000000 > >> [ 0.000000] x15: ffffffffffffffff3: 0000000fc18d0000 x12: 0000000800000000 > >> [ 0.000000] x11: 0000000000000018 x10: 00000000ddab9e18 > >> [ 0.000000] x9 : 0000000800000000 x8 : 00000000000002c1 > >> [ 0.000000] x7 : 0000000091b90000 x6 : ffff80003ffe0000 > >> [ 0.000000] x5 : 0000000000000001 x4 : 0000000000000000 > >> [ 0.000000] x3 : 0000000000000000 x2 : 0000000000000b80 > >> [ 0.000000] x1 : ffff000009d59540 x0 : ffff80003ffe0000 > >> [ 0.000000] Process swapper) > >> [ 0.000000] Call trace: > >> [ 0.000000] __memcpy+0x110/0x180 > >> [ 0.000000] memblock_add_range+0x134/0x2e8 > >> [ 0.000000] memblock_reserve+0x70/0xb8 > >> [ 0.000000] memblock_alloc_base_nid+0x6c/0x88 > >> [ 0.000000] __memblock_alloc_base+0x3c/0x4c > >> [ 0.000000] memblock_alloc_base+0x28/0x4c > >> [ 0.000000] memblock_alloc+0x2c/0x38 > >> [ 0.000000] early_pgtable_alloc+0x20/0xb0 > > > > Hmm, so this seems to be the crux of the issue: early_pgtable_alloc() relies > > on memblock to allocate page-table memory, but this can be called before the > > linear mapping is up and running (or even as part of creating the linear > > mapping itself!) so the use of __va in memblock_double_array() actually > > returns an unmapped address. > > > > OK, so this means we are calling memblock_allow_resize() too early in any case > > > So I guess we either need to implement early_pgtable_alloc() some other way > > (how?) or get memblock_double_array() to use a fixmap if it's called too > > early (yuck). Alternatively, would it be possible to postpone processing of > > the EFI mem_reserve entries until after we've created the linear mapping? > > > > We could move this until after paging_init(), I suppose. I'll cook something up. > > Bhupesh: any comments? Since Ard has already shared a patchset which seems to fix this issue [Thanks Ard :)], and my approach is still hackish, I will try to verify his v2 patchset on the system I was having issues with and get back with my results. Thanks for all the help. Regards, Bhupesh
