Re: [PATCH AUTOSEL 6.6 14/17] um: virt-pci: don't use kmalloc()

Johannes Berg
2025-02-19T07:42:20Z

On Tue, 2025-02-18 at 15:27 -0500, Sasha Levin wrote:
> From: Johannes Berg <johannes.berg@intel.com>
>
> [ Upstream commit 5b166b782d327f4b66190cc43afd3be36f2b3b7a ]
>
> This code can be called deep in the IRQ handling, for
> example, and then cannot normally use kmalloc(). Have
> its own pre-allocated memory and use from there instead
> so this doesn't occur. Only in the (very rare) case of
> memcpy_toio() we'd still need to allocate memory.

I don't believe this patch, "um: convert irq_lock to raw spinlock" and
"um: virtio_uml: use raw spinlock", are relevant to anything older than
6.12. I don't see how applying them would _hurt_, but I didn't have them
before 6.12 and had no lockdep complaints about it; I believe some other
internal IRQ rework caused the issues to pop up.

Never mind that we (Intel WiFi stuff) are probably the only ones ever
running this virtio_uml/virt-pci with lockdep :)

johannes