https://bugzilla.kernel.org/show_bug.cgi?id=209253 --- Comment #5 from Ian Pilcher (arequipeno@xxxxxxxxx) --- Based on my git bisect, it looks like this commit is triggering the WARNING. commit c49fa6397b6d29ce10c0ae5b2528bb004a14691f Author: Alex Williamson <alex.williamson@xxxxxxxxxx> Date: Mon Aug 17 11:08:18 2020 -0600 vfio-pci: Avoid recursive read-lock usage [ Upstream commit bc93b9ae0151ae5ad5b8504cdc598428ea99570b ] A down_read on memory_lock is held when performing read/write accesses to MMIO BAR space, including across the copy_to/from_user() callouts which may fault. If the user buffer for these copies resides in an mmap of device MMIO space, the mmap fault handler will acquire a recursive read-lock on memory_lock. Avoid this by reducing the lock granularity. Sequential accesses requiring multiple ioread/iowrite cycles are expected to be rare, therefore typical accesses should not see additional overhead. VGA MMIO accesses are expected to be non-fatal regardless of the PCI memory enable bit to allow legacy probing, this behavior remains with a comment added. ioeventfds are now included in memory access testing, with writes dropped while memory space is disabled. Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory") Reported-by: Zhiyi Guo <zhguo@xxxxxxxxxx> Tested-by: Zhiyi Guo <zhguo@xxxxxxxxxx> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> drivers/vfio/pci/vfio_pci_private.h | 2 + drivers/vfio/pci/vfio_pci_rdwr.c | 120 ++++++++++++++++++++++++++++-------- 2 files changed, 98 insertions(+), 24 deletions(-) https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bc93b9ae0151ae5ad5b8504cdc598428ea99570b -- You are receiving this mail because: You are watching the assignee of the bug.
