On Mon, 13 Apr 2026 03:45:20 -0400
"Michael S. Tsirkin" <[email protected]> wrote:
> On Mon, Apr 13, 2026 at 03:22:49PM +0800, Jinhui Guo wrote:
> > virtqueue_exec_admin_cmd() holds admin_vq->lock with spin_lock_irqsave(),
> > which disables interrupts. Using GFP_KERNEL inside this critical section
> > is unsafe because kmalloc() may sleep, leading to potential deadlocks or
> > scheduling violations.
> >
> > Switch to GFP_ATOMIC to ensure the allocation is non-blocking.
> >
> > Fixes: 4c3b54af907e ("virtio_pci_modern: use completion instead of busy
> > loop to wait on admin cmd result")
> > Cc: [email protected]
> > Signed-off-by: Jinhui Guo <[email protected]>
> > ---
> > drivers/virtio/virtio_pci_modern.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_modern.c
> > b/drivers/virtio/virtio_pci_modern.c
> > index 6d8ae2a6a8ca..db8e4f88b749 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -101,7 +101,7 @@ static int virtqueue_exec_admin_cmd(struct
> > virtio_pci_admin_vq *admin_vq,
> > return -EIO;
> >
> > spin_lock_irqsave(&admin_vq->lock, flags);
> > - ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_KERNEL);
> > + ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_ATOMIC);
> > if (ret < 0) {
> > if (ret == -ENOSPC) {
> > spin_unlock_irqrestore(&admin_vq->lock, flags);
>
>
> GFP_ATOMIC allocations can and will fail. If using them, one must
> retry, not just propagate failures.
> Or just switch admin_vq->lock to a mutex?
Or do the allocate before acquiring the lock (and free it not used
in the error path).
David
>
>
> > --
> > 2.20.1
>
>
