diff options
| author | Keith Busch <kbusch@kernel.org> | 2025-07-15 11:46:22 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-20 18:30:47 +0200 |
| commit | bcbad21fe9bee6ebfeb10bd14c553237caced2f3 (patch) | |
| tree | 463ed5af3b1da96e1ebfdd01a52bfabd5fda9d76 | |
| parent | d850808db603ed9778b128f6f4c2f9f2a7c6d029 (diff) | |
vfio/type1: conditional rescheduling while pinning
[ Upstream commit b1779e4f209c7ff7e32f3c79d69bca4e3a3a68b6 ]
A large DMA mapping request can loop through dma address pinning for
many pages. In cases where THP can not be used, the repeated vmf_insert_pfn can
be costly, so let the task reschedule as need to prevent CPU stalls. Failure to
do so has potential harmful side effects, like increased memory pressure
as unrelated rcu tasks are unable to make their reclaim callbacks and
result in OOM conditions.
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 36-....: (20999 ticks this GP) idle=b01c/1/0x4000000000000000 softirq=35839/35839 fqs=3538
rcu: hardirqs softirqs csw/system
rcu: number: 0 107 0
rcu: cputime: 50 0 10446 ==> 10556(ms)
rcu: (t=21075 jiffies g=377761 q=204059 ncpus=384)
...
<TASK>
? asm_sysvec_apic_timer_interrupt+0x16/0x20
? walk_system_ram_range+0x63/0x120
? walk_system_ram_range+0x46/0x120
? pgprot_writethrough+0x20/0x20
lookup_memtype+0x67/0xf0
track_pfn_insert+0x20/0x40
vmf_insert_pfn_prot+0x88/0x140
vfio_pci_mmap_huge_fault+0xf9/0x1b0 [vfio_pci_core]
__do_fault+0x28/0x1b0
handle_mm_fault+0xef1/0x2560
fixup_user_fault+0xf5/0x270
vaddr_get_pfns+0x169/0x2f0 [vfio_iommu_type1]
vfio_pin_pages_remote+0x162/0x8e0 [vfio_iommu_type1]
vfio_iommu_type1_ioctl+0x1121/0x1810 [vfio_iommu_type1]
? futex_wake+0x1c1/0x260
x64_sys_call+0x234/0x17a0
do_syscall_64+0x63/0x130
? exc_page_fault+0x63/0x130
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20250715184622.3561598-1-kbusch@meta.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/vfio/vfio_iommu_type1.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 8338cfd61fe1..124997ce00d6 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -619,6 +619,13 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr, while (npage) { if (!batch->size) { + /* + * Large mappings may take a while to repeatedly refill + * the batch, so conditionally relinquish the CPU when + * needed to avoid stalls. + */ + cond_resched(); + /* Empty batch, so refill it. */ long req_pages = min_t(long, npage, batch->capacity); |