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Re: [Qemu-block] [Qemu-devel] [PATCH v2 0/6] ide: fix atapi software res

From: John Snow
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH v2 0/6] ide: fix atapi software reset
Date: Tue, 26 Jan 2016 15:39:14 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0


(I know I could just send a PR, but in this case I'd like someone to
look over it. I've gone over pretty terrible detail to convince myself
this won't break anything IDE-wise, so if it looks sane block-wise, I'd
be satisfied with an ACK.)

On 01/19/2016 12:39 PM, John Snow wrote:
> The ATAPI software reset function is implemented somewhat lackadaisically.
> Firstly, it is valid only for ATAPI drives - not HDs. If a HD should
> receive this command while BSY, it should be ignored like any other
> command instead of aborted. A non-BSY HD is free to abort the command
> in the usual fashion to indicate it doesn't understand or doesn't support
> that command.
> Second, for drives that should accept a software reset, they should not
> "forget" about all pending AIO during the reset. Since a software reset
> resets the DRQ and BSY flags, it is possible to 'stack' multiple
> concurrent reads using DMA and alternately chaining software reset and
> DMA reads. We mustn't reset BSY/DRQ until we are confident that we
> have canceled existing AIO.
> Third, the existing software reset routine does not perform a very
> rigorous reset.
> This series corrects this by:
> (1) Correcting ide_exec_cmd to correctly ignore, not abort, software
>     reset commands for ide-hd devices that are busy executing a command.
> (2) Improving the software reset routine to cancel buffered DMA, then
>     fall back to synchronously waiting for any pending DMA to finish
>     before returning, insuring that the reset completes sanely.
> (3) Use existing reset routines to comprehensively reset the device.
> Reported-by: Kevin Wolf <address@hidden>
> Signed-off-by: John Snow <address@hidden>
> ________________________________________________________________________________
> For convenience, this branch is available at:
> https://github.com/jnsnow/qemu.git branch ide-reset-fix
> https://github.com/jnsnow/qemu/tree/ide-reset-fix
> This version is tagged ide-reset-fix-v2:
> https://github.com/jnsnow/qemu/releases/tag/ide-reset-fix-v2
> John Snow (6):
>   ide: Prohibit RESET on IDE drives
>   ide: code motion
>   ide: move buffered DMA cancel to core
>   ide: replace blk_drain_all by blk_drain
>   ide: Add silent DRQ cancellation
>   ide: fix device_reset to not ignore pending AIO
>  hw/ide/core.c     | 215 
> ++++++++++++++++++++++++++++++++++++------------------
>  hw/ide/internal.h |   1 +
>  hw/ide/pci.c      |  36 +--------
>  3 files changed, 144 insertions(+), 108 deletions(-)

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