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Re: [Qemu-block] [PATCH 1/4] IDE: Do not flush empty CDROM drives
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH 1/4] IDE: Do not flush empty CDROM drives |
Date: |
Wed, 9 Aug 2017 10:34:42 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Tue, Aug 08, 2017 at 01:57:08PM -0400, John Snow wrote:
> The block backend changed in a way that flushing empty CDROM drives
> is now an error. Amend IDE to avoid doing so until the root problem
> can be addressed for 2.11.
>
> Reported-by: Kieron Shorrock <address@hidden>
> Signed-off-by: John Snow <address@hidden>
> ---
> hw/ide/core.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index 0b48b64..6cbca43 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -1053,17 +1053,21 @@ static void ide_flush_cb(void *opaque, int ret)
> ide_set_irq(s->bus);
> }
>
> -static void ide_flush_cache(IDEState *s)
> +static bool ide_flush_cache(IDEState *s)
Previously this function invoked ide_flush_cb() to complete the request
and raise an IRQ. Now it may return true instead of invoking
ide_flush_cb(). It's no longer a helper function, it's more like an IDE
command handler.
cmd_set_features() must be updated:
case 0x82: /* write cache disable */
blk_set_enable_write_cache(s->blk, false);
identify_data = (uint16_t *)s->identify_data;
put_le16(identify_data + 85, (1 << 14) | 1);
ide_flush_cache(s);
return false; <--- should be "return ide_flush_cache(s)"
To make the code clearer I suggest deleting ide_flush_cache() and
calling cmd_flush_cache() directly instead. That way it's obvious that
this is an IDE command handler and it may return true to indicate the
the command completed immediately.
> {
> if (s->blk == NULL) {
> ide_flush_cb(s, 0);
> - return;
> + return false;
> + } else if (!blk_bs(s->blk)) {
> + /* Nothing to flush */
Please move information from the commit description into this comment if
you respin. Someone looking at the code might think this is a nop that
is safe to remove. Once blk_*() is fixed this code path can be removed
again.
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