Re: Regression in linux-next

[Alistair Popple <apopple@nvidia.com>]

Thanks Chaitanya for the detailed report. Dan Carpenter also reported a
Smatch warning for this:

https://lore.kernel.org/linux-mm/38ed0627-1283-4da2-827a-e90484d7bd7d@moroto.mountain/

The below should fix the problem, will respin the series to include the
fix.

---

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 63c8eb740af7..ec3b068cbbe6 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -621,9 +621,10 @@ int __mmu_notifier_register(struct mmu_notifier *subscription,
 	 * Subsystems should only register for invalidate_secondary_tlbs() or
 	 * invalidate_range_start()/end() callbacks, not both.
 	 */
-	if (WARN_ON_ONCE(subscription->ops->arch_invalidate_secondary_tlbs &&
-				(subscription->ops->invalidate_range_start ||
-				subscription->ops->invalidate_range_end)))
+	if (WARN_ON_ONCE(subscription &&
+			 (subscription->ops->arch_invalidate_secondary_tlbs &&
+			 (subscription->ops->invalidate_range_start ||
+			  subscription->ops->invalidate_range_end))))
 		return -EINVAL;
 
 	if (!mm->notifier_subscriptions) {


"Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com> writes:

> Hello Alistair,
>
> Hope you are doing well. I am Chaitanya from the linux graphics team in Intel.
>  
> This mail is regarding a regression we are seeing in our CI runs[1] on linux-next
> repository.
>  
> On next-20230720 [2], we are seeing the following error
>
> <4>[   76.189375] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P DDR5 SODIMM SBS RVP, BIOS MTLPFWI1.R00.3271.D81.2307101805 07/10/2023
> <4>[   76.202534] RIP: 0010:__mmu_notifier_register+0x40/0x210
> <4>[ 76.207804] Code: 1a 71 5a 01 85 c0 0f 85 ec 00 00 00 48 8b 85 30
> 01 00 00 48 85 c0 0f 84 04 01 00 00 8b 85 cc 00 00 00 85 c0 0f 8e bb
> 01 00 00 <49> 8b 44 24 10 48 83 78 38 00 74 1a 48 83 78 28 00 74 0c 0f
> 0b b8
> <4>[   76.226368] RSP: 0018:ffffc900019d7ca8 EFLAGS: 00010202
> <4>[   76.231549] RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000000001
> <4>[   76.238613] RDX: 0000000000000000 RSI: ffffffff823ceb7b RDI: ffffffff823ee12d
> <4>[   76.245680] RBP: ffff888102ec9b40 R08: 00000000ffffffff R09: 0000000000000001
> <4>[   76.252747] R10: 0000000000000001 R11: ffff8881157cd2c0 R12: 0000000000000000
> <4>[   76.259811] R13: ffff888102ec9c70 R14: ffffffffa07de500 R15: ffff888102ec9ce0
> <4>[   76.266875] FS:  00007fbcabe11c00(0000) GS:ffff88846ec00000(0000) knlGS:0000000000000000
> <4>[   76.274884] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> <4>[   76.280578] CR2: 0000000000000010 CR3: 000000010d4c2005 CR4: 0000000000f70ee0
> <4>[   76.287643] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> <4>[   76.294711] DR3: 0000000000000000 DR6: 00000000ffff07f0 DR7: 0000000000000400
> <4>[   76.301775] PKRU: 55555554
> <4>[   76.304463] Call Trace:
> <4>[   76.306893]  <TASK>
> <4>[   76.308983]  ? __die_body+0x1a/0x60
> <4>[   76.312444]  ? page_fault_oops+0x156/0x450
> <4>[   76.316510]  ? do_user_addr_fault+0x65/0x980
> <4>[   76.320747]  ? exc_page_fault+0x68/0x1a0
> <4>[   76.324643]  ? asm_exc_page_fault+0x26/0x30
> <4>[   76.328796]  ? __mmu_notifier_register+0x40/0x210
> <4>[   76.333460]  ? __mmu_notifier_register+0x11c/0x210
> <4>[   76.338206]  ? preempt_count_add+0x4c/0xa0
> <4>[   76.342273]  mmu_notifier_register+0x30/0xe0
> <4>[   76.346509]  mmu_interval_notifier_insert+0x74/0xb0
> <4>[   76.351344]  i915_gem_userptr_ioctl+0x21a/0x320 [i915]
> <4>[   76.356565]  ? __pfx_i915_gem_userptr_ioctl+0x10/0x10 [i915]
> <4>[   76.362271]  drm_ioctl_kernel+0xb4/0x150
> <4>[   76.366159]  drm_ioctl+0x21d/0x420
> <4>[   76.369537]  ? __pfx_i915_gem_userptr_ioctl+0x10/0x10 [i915]
> <4>[   76.375242]  ? find_held_lock+0x2b/0x80
> <4>[   76.379046]  __x64_sys_ioctl+0x79/0xb0
> <4>[   76.382766]  do_syscall_64+0x3c/0x90
> <4>[   76.386312]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> <4>[   76.391317] RIP: 0033:0x7fbcae63f3ab
>
> Details log can be found in [3].
>
> After bisecting the tree, the following patch seems to be causing the
> regression.
>
> commit 828fe4085cae77acb3abf7dd3d25b3ed6c560edf
> Author: Alistair Popple apopple@nvidia.com
> Date:   Wed Jul 19 22:18:46 2023 +1000
>
>     mmu_notifiers: rename invalidate_range notifier
>
>     There are two main use cases for mmu notifiers.  One is by KVM which uses
>     mmu_notifier_invalidate_range_start()/end() to manage a software TLB.
>
>     The other is to manage hardware TLBs which need to use the
>     invalidate_range() callback because HW can establish new TLB entries at
>     any time.  Hence using start/end() can lead to memory corruption as these
>     callbacks happen too soon/late during page unmap.
>
>     mmu notifier users should therefore either use the start()/end() callbacks
>     or the invalidate_range() callbacks.  To make this usage clearer rename
>     the invalidate_range() callback to arch_invalidate_secondary_tlbs() and
>     update documention.
>
>     Link: https://lkml.kernel.org/r/9a02dde2f8ddaad2db31e54706a80c12d1817aaf.1689768831.git-series.apopple@nvidia.com
>
>
> We also verified by reverting the patch in the tree.
>
> Could you please check why this patch causes the regression and if we can find
> a solution for it soon?
>
> [1] https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20230720 
> [3] https://intel-gfx-ci.01.org/tree/linux-next/next-20230720/bat-mtlp-6/dmesg0.txt