Re: [PATCH] virtio_console: allocate the port_buffer with the caller's gfp

[Breno Leitao]

On Wed, Aug 19, 2026 at 08:36:25PM +0900, Sungho Bae wrote:
> >
> > put_chars() runs from the hvc console write path with preemption
> > disabled, so it asks alloc_buf() for GFP_ATOMIC. Only the data buffer
> > gets it: the struct port_buffer itself keeps the GFP_KERNEL default, so
> > the allocation can enter direct reclaim and sleep. A write to /dev/kmsg
> > on a CONFIG_DEBUG_ATOMIC_SLEEP kernel splats:
> >
> >   BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:320
> >   in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1, name: virtme-ng-init
> >   preempt_count: 1, expected: 0
> >   Preemption disabled at:
> >   [<ffffffff813fd90d>] vprintk_emit+0x17d/0x510
> >   Call Trace:
> >    <TASK>
> >    dump_stack_lvl+0x69/0xa0
> >    __might_resched+0x37a/0x4d0
> >    __kmalloc_cache_noprof+0x94/0x5f0
> >    put_chars+0x209/0x3e0
> >    hvc_console_print+0x234/0x640
> >    console_flush_all+0x4fc/0x950
> >    console_unlock+0xbf/0x1b0
> >    vprintk_emit+0x312/0x510
> >    devkmsg_emit+0xba/0x110
> >    devkmsg_write+0x21b/0x2e0
> >    vfs_write+0x4dc/0x9d0
> >    ksys_write+0x108/0x1e0
> >    do_syscall_64+0xfa/0x460
> >    </TASK>
> >
> > Pass gfp on to that allocation too.
> >
> > Fixes: fc220d6be3c7 ("virtio_console: refactor __send_to_port() buffer ownership")
> > Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
> 
> Acked-by: Sungho Bae <baver.bae@xxxxxxx>

Greg, are you the one that should pick this up?

The regression fixed here is now on Linus' tree.

Thanks
--breno