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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Tue, 20 Feb 2018 22:54:35 +0100
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Subject: Re: [Qemu-devel] [Qemu-block] Limiting coroutine stack usage
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To: Peter Lieven <pl@kamp.de>, qemu block <qemu-block@nongnu.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On 20/02/2018 18:04, Peter Lieven wrote:
> Hi,
> 
> I remember we discussed a long time ago to limit the stack usage of all
> functions that are executed in a coroutine
> context to a very low value to be able to safely limit the coroutine
> stack size as well.

IIRC the only issue was that hw/ide/atapi.c has mutual recursion between
ide_atapi_cmd_reply_end -> ide_transfer_start -> ahci_start_transfer ->
ide_atapi_cmd_reply_end.

But perhaps it's not an issue, somebody needs to audit the code.

> I checked through all functions in block/, migration/ and nbd/ and there
> are only very few larger or unbound stack
> allocations that can easily be fixed.

Yeah, the really large allocations are very few and mostly have to do
with networking (https://wiki.qemu.org/BiteSizedTasks#Large_frames).
Unfortunately the link to the original list has died together with the
gmane archives.

Paolo