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Re: Use of BQL from thread in PCIe device
From: |
John Levon |
Subject: |
Re: Use of BQL from thread in PCIe device |
Date: |
Wed, 18 Dec 2024 17:28:16 +0000 |
On Wed, Dec 18, 2024 at 04:19:47PM +0000, Markus Lavin wrote:
> Hi,
>
> I think that I might have misunderstood something fundamental about the BQL
> (or possibly Qemu in general).
>
> I have a custom PCIe device that connects to an outside simulation environment
> using Unix domain sockets. To deal with bus-mastering from this outside
> environment I have a thread created with qemu_thread_create listening to the
> socket.
>
> If I get a read/write/interrupt request over the socket then the thread should
> perform a pci_dma_read/pci_dma_write/msix_notify. Since this is called from
> the threads context I assumed I should first grab the BQL. Issuing a bql_lock
> from the thread however hangs Qemu.
>
> Is my thinking flawed?
The BQL will be already taken for these callbacks higher up in the stack I
believe.
regards
john