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Re: [Qemu-block] [Qemu-devel] [RFC PATCH 0/5] atapi: change unlimited re

From: John Snow
Subject: Re: [Qemu-block] [Qemu-devel] [RFC PATCH 0/5] atapi: change unlimited recursion to while loop
Date: Tue, 27 Feb 2018 23:21:07 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

On 02/23/2018 10:26 AM, Paolo Bonzini wrote:
> Real hardware doesn't have an unlimited stack, so the unlimited
> recursion in the ATAPI code smells a bit.  In fact, the call to
> ide_transfer_start easily becomes a tail call with a small change
> to the code (patch 4).  The remaining four patches move code around
> so as to the turn the call back to ide_atapi_cmd_reply_end into
> another tail call, and then convert the (double) tail recursion into
> a while loop.
> I'm not sure how this can be tested, apart from adding a READ CD
> test to ahci-test (which I don't really have time for now, hence
> the RFC tag).  The existing AHCI tests still pass, so patches 1-3
> aren't complete crap.
> Paolo
> Paolo Bonzini (5):
>   ide: push call to end_transfer_func out of start_transfer callback
>   ide: push end_transfer callback to ide_transfer_halt
>   ide: make ide_transfer_stop idempotent
>   atapi: call ide_set_irq before ide_transfer_start
>   ide: introduce ide_transfer_start_norecurse
>  hw/ide/ahci.c             | 12 +++++++-----
>  hw/ide/atapi.c            | 37 ++++++++++++++++++++-----------------
>  hw/ide/core.c             | 37 +++++++++++++++++++++++--------------
>  include/hw/ide/internal.h |  3 +++
>  4 files changed, 53 insertions(+), 36 deletions(-)

ACK receipt, I will get to this soon, sorry!

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