On Wed, 21 Aug 2024 17:47:06 +0100, Darren Kenny <darren.kenny@xxxxxxxxxx> wrote:
>
> Hi Michael,
>
> On Tuesday, 2024-08-20 at 12:50:39 -04, Michael S. Tsirkin wrote:
> > On Tue, Aug 20, 2024 at 03:19:13PM +0800, Xuan Zhuo wrote:
> >> leads to regression on VM with the sysctl value of:
> >>
> >> - net.core.high_order_alloc_disable=1
> >
> >
> >
> >
> >> which could see reliable crashes or scp failure (scp a file 100M in size
> >> to VM):
> >>
> >> The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning
> >> of a new frag. When the frag size is larger than PAGE_SIZE,
> >> everything is fine. However, if the frag is only one page and the
> >> total size of the buffer and virtnet_rq_dma is larger than one page, an
> >> overflow may occur. In this case, if an overflow is possible, I adjust
> >> the buffer size. If net.core.high_order_alloc_disable=1, the maximum
> >> buffer size is 4096 - 16. If net.core.high_order_alloc_disable=0, only
> >> the first buffer of the frag is affected.
> >>
> >> Fixes: f9dac92ba908 ("virtio_ring: enable premapped mode whatever use_dma_api")
> >> Reported-by: "Si-Wei Liu" <si-wei.liu@xxxxxxxxxx>
> >> Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@xxxxxxxxxx
> >> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> >
> >
> > Darren, could you pls test and confirm?
>
> Unfortunately with this change I seem to still get a panic as soon as I start a
> download using wget:
It's strange that I can't reproduce your panic.
My test method is to test with net.core.high_order_alloc_disable=1 on the net
branch code. An exception soon occurred (connection disconnected), and then
the kernel panicked.
while true; do scp vmlinux root@192.168.122.100:; done
Use this patch to recompile virtio_net.ko, restart, configure
net.core.high_order_alloc_disable=1 again, and test for a long time without
problems.
So, could you re-test?
Thanks.
>
> [ 144.055630] Kernel panic - not syncing: corrupted stack end detected inside scheduler
> [ 144.056249] CPU: 8 PID: 37894 Comm: sleep Kdump: loaded Not tainted 6.10.0-1.el8uek.x86_64 #2
> [ 144.056850] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-4.module+el8.9.0+90173+a3f3e83a 04/01/2014
> [ 144.057585] Call Trace:
> [ 144.057791] <TASK>
> [ 144.057973] panic+0x347/0x370
> [ 144.058223] schedule_debug.isra.0+0xfb/0x100
> [ 144.058565] __schedule+0x58/0x6a0
> [ 144.058838] ? refill_stock+0x26/0x50
> [ 144.059120] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.059473] do_task_dead+0x42/0x50
> [ 144.059752] do_exit+0x31e/0x4b0
> [ 144.060011] ? __audit_syscall_entry+0xee/0x150
> [ 144.060352] do_group_exit+0x30/0x80
> [ 144.060633] __x64_sys_exit_group+0x18/0x20
> [ 144.060946] do_syscall_64+0x8c/0x1c0
> [ 144.061228] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.061570] ? __audit_filter_op+0xbe/0x140
> [ 144.061873] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.062204] ? audit_reset_context+0x232/0x310
> [ 144.062514] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.062851] ? syscall_exit_work+0x103/0x130
> [ 144.063148] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.063473] ? syscall_exit_to_user_mode+0x77/0x220
> [ 144.063813] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.064142] ? do_syscall_64+0xb9/0x1c0
> [ 144.064411] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.064747] ? do_syscall_64+0xb9/0x1c0
> [ 144.065018] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.065345] ? do_read_fault+0x109/0x1b0
> [ 144.065628] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.065961] ? do_fault+0x1aa/0x2f0
> [ 144.066212] ? handle_pte_fault+0x102/0x1a0
> [ 144.066503] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.066836] ? __handle_mm_fault+0x5ed/0x710
> [ 144.067137] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.067464] ? __count_memcg_events+0x72/0x110
> [ 144.067779] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.068106] ? count_memcg_events.constprop.0+0x26/0x50
> [ 144.068457] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.068788] ? handle_mm_fault+0xae/0x320
> [ 144.069068] ? srso_alias_return_thunk+0x5/0xfbef5
> [ 144.069395] ? do_user_addr_fault+0x34a/0x6b0
> [ 144.069708] entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [ 144.070049] RIP: 0033:0x7fc5524f9c66
> [ 144.070307] Code: Unable to access opcode bytes at 0x7fc5524f9c3c.
> [ 144.070720] RSP: 002b:00007ffee052beb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> [ 144.071214] RAX: ffffffffffffffda RBX: 00007fc5527bb860 RCX: 00007fc5524f9c66
> [ 144.071684] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
> [ 144.072146] RBP: 0000000000000000 R08: 00000000000000e7 R09: ffffffffffffff78
> [ 144.072608] R10: 00007ffee052bdef R11: 0000000000000246 R12: 00007fc5527bb860
> [ 144.073076] R13: 0000000000000002 R14: 00007fc5527c4528 R15: 0000000000000000
> [ 144.073543] </TASK>
> [ 144.074780] Kernel Offset: 0x37c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
>
> Thanks,
>
> Darren.
>
> >> ---
> >> drivers/net/virtio_net.c | 12 +++++++++---
> >> 1 file changed, 9 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >> index c6af18948092..e5286a6da863 100644
> >> --- a/drivers/net/virtio_net.c
> >> +++ b/drivers/net/virtio_net.c
> >> @@ -918,9 +918,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> >> void *buf, *head;
> >> dma_addr_t addr;
> >>
> >> - if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
> >> - return NULL;
> >> -
> >> head = page_address(alloc_frag->page);
> >>
> >> dma = head;
> >> @@ -2421,6 +2418,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
> >> len = SKB_DATA_ALIGN(len) +
> >> SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> >>
> >> + if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
> >> + return -ENOMEM;
> >> +
> >> buf = virtnet_rq_alloc(rq, len, gfp);
> >> if (unlikely(!buf))
> >> return -ENOMEM;
> >> @@ -2521,6 +2521,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> >> */
> >> len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
> >>
> >> + if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> >> + return -ENOMEM;
> >> +
> >> + if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
> >> + len -= sizeof(struct virtnet_rq_dma);
> >> +
> >> buf = virtnet_rq_alloc(rq, len + room, gfp);
> >> if (unlikely(!buf))
> >> return -ENOMEM;
> >> --
> >> 2.32.0.3.g01195cf9f
>
>
