From: Juergen Gross jgross@suse.com
commit 36c9b5929b7094ea19a78827c0ede20d2e0e6c9c upstream.
Commit 0881ace292b662 ("mm/mremap: use pmd/pud_poplulate to update page table entries") introduced a regression when running as Xen PV guest.
Today pmd_populate() for Xen PV assumes that the PFN inserted is referencing a not yet used page table. In case of move_normal_pmd() this is not true, resulting in WARN splats like:
[34321.304270] ------------[ cut here ]------------ [34321.304277] WARNING: CPU: 0 PID: 23628 at arch/x86/xen/multicalls.c:102 xen_mc_flush+0x176/0x1a0 [34321.304288] Modules linked in: [34321.304291] CPU: 0 PID: 23628 Comm: apt-get Not tainted 5.14.1-20210906-doflr-mac80211debug+ #1 [34321.304294] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640) , BIOS V1.8B1 09/13/2010 [34321.304296] RIP: e030:xen_mc_flush+0x176/0x1a0 [34321.304300] Code: 89 45 18 48 c1 e9 3f 48 89 ce e9 20 ff ff ff e8 60 03 00 00 66 90 5b 5d 41 5c 41 5d c3 48 c7 45 18 ea ff ff ff be 01 00 00 00 <0f> 0b 8b 55 00 48 c7 c7 10 97 aa 82 31 db 49 c7 c5 38 97 aa 82 65 [34321.304303] RSP: e02b:ffffc90000a97c90 EFLAGS: 00010002 [34321.304305] RAX: ffff88807d416398 RBX: ffff88807d416350 RCX: ffff88807d416398 [34321.304306] RDX: 0000000000000001 RSI: 0000000000000001 RDI: deadbeefdeadf00d [34321.304308] RBP: ffff88807d416300 R08: aaaaaaaaaaaaaaaa R09: ffff888006160cc0 [34321.304309] R10: deadbeefdeadf00d R11: ffffea000026a600 R12: 0000000000000000 [34321.304310] R13: ffff888012f6b000 R14: 0000000012f6b000 R15: 0000000000000001 [34321.304320] FS: 00007f5071177800(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000 [34321.304322] CS: 10000e030 DS: 0000 ES: 0000 CR0: 0000000080050033 [34321.304323] CR2: 00007f506f542000 CR3: 00000000160cc000 CR4: 0000000000000660 [34321.304326] Call Trace: [34321.304331] xen_alloc_pte+0x294/0x320 [34321.304334] move_pgt_entry+0x165/0x4b0 [34321.304339] move_page_tables+0x6fa/0x8d0 [34321.304342] move_vma.isra.44+0x138/0x500 [34321.304345] __x64_sys_mremap+0x296/0x410 [34321.304348] do_syscall_64+0x3a/0x80 [34321.304352] entry_SYSCALL_64_after_hwframe+0x44/0xae [34321.304355] RIP: 0033:0x7f507196301a [34321.304358] Code: 73 01 c3 48 8b 0d 76 0e 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 19 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 46 0e 0c 00 f7 d8 64 89 01 48 [34321.304360] RSP: 002b:00007ffda1eecd38 EFLAGS: 00000246 ORIG_RAX: 0000000000000019 [34321.304362] RAX: ffffffffffffffda RBX: 000056205f950f30 RCX: 00007f507196301a [34321.304363] RDX: 0000000001a00000 RSI: 0000000001900000 RDI: 00007f506dc56000 [34321.304364] RBP: 0000000001a00000 R08: 0000000000000010 R09: 0000000000000004 [34321.304365] R10: 0000000000000001 R11: 0000000000000246 R12: 00007f506dc56060 [34321.304367] R13: 00007f506dc56000 R14: 00007f506dc56060 R15: 000056205f950f30 [34321.304368] ---[ end trace a19885b78fe8f33e ]--- [34321.304370] 1 of 2 multicall(s) failed: cpu 0 [34321.304371] call 2: op=12297829382473034410 arg=[aaaaaaaaaaaaaaaa] result=-22
Fix that by modifying xen_alloc_ptpage() to only pin the page table in case it wasn't pinned already.
Fixes: 0881ace292b662 ("mm/mremap: use pmd/pud_poplulate to update page table entries") Cc: stable@vger.kernel.org Reported-by: Sander Eikelenboom linux@eikelenboom.it Tested-by: Sander Eikelenboom linux@eikelenboom.it Signed-off-by: Juergen Gross jgross@suse.com Link: https://lore.kernel.org/r/20210908073640.11299-1-jgross@suse.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/xen/mmu_pv.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -1518,14 +1518,17 @@ static inline void xen_alloc_ptpage(stru if (pinned) { struct page *page = pfn_to_page(pfn);
- if (static_branch_likely(&xen_struct_pages_ready)) + pinned = false; + if (static_branch_likely(&xen_struct_pages_ready)) { + pinned = PagePinned(page); SetPagePinned(page); + }
xen_mc_batch();
__set_pfn_prot(pfn, PAGE_KERNEL_RO);
- if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS) + if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS && !pinned) __pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn);
xen_mc_issue(PARAVIRT_LAZY_MMU);