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Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom |
Date: |
Wed, 08 Jul 2015 12:47:57 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 08/07/2015 12:31, Kevin Wolf wrote:
> Am 02.07.2015 um 16:18 hat Laurent Vivier geschrieben:
>>
>>
>> On 02/07/2015 16:03, Paolo Bonzini wrote:
>>>
>>>
>>> On 02/07/2015 15:58, Laurent Vivier wrote:
>>>> Since any /dev entry can be treated as a raw disk image, it is worth
>>>> noting which devices can be accessed when and how. /dev/rdisk nodes are
>>>> character-special devices, but are "raw" in the BSD sense and force
>>>> block-aligned I/O. They are closer to the physical disk than the buffer
>>>> cache. /dev/disk nodes, on the other hand, are buffered block-special
>>>> devices and are used primarily by the kernel's filesystem code.
>>>
>>> So the right thing to do would not be just to set need_alignment, but to
>>> probe it like we do on Linux for BDRV_O_NO_CACHE.
>>>
>>> I'm okay with doing the simple thing, but it needs a comment for non-BSDers.
>>
>> So, what we have to do, in our case, for MacOS X cdrom, is something like:
>>
>> ... GetBSDPath ...
>> ...
>> if (flags & BDRV_O_NOCACHE) {
>> strcat(bsdPath, "r");
>> }
>> ...
>
> I would avoid such magic. What we could do is rejecting /dev/rdisk nodes
> without BDRV_O_NOCACHE.
It's not how it works...
Look in hdev_open().
If user provides /dev/cdrom on the command line, in the case of MacOS X,
QEMU searches for a cdrom drive in the system and set filename to
/dev/rdiskX according to the result.
Perhaps this part should be removed.
But if we just want to correct the bug, we must not set filename to
/dev/rdiskX if NOCACHE is not set but to /dev/diskX
It's the aim of this change.
Laurent
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, (continued)
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Laurent Vivier, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Paolo Bonzini, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Laurent Vivier, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Paolo Bonzini, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Laurent Vivier, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Paolo Bonzini, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Laurent Vivier, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Programmingkid, 2015/07/02
- Re: [Qemu-devel] [PATCH v2] raw-posix.c: remove raw device access for cdrom, Programmingkid, 2015/07/02
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Kevin Wolf, 2015/07/08
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom,
Laurent Vivier <=
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Kevin Wolf, 2015/07/08
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Programmingkid, 2015/07/08
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Kevin Wolf, 2015/07/08
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Programmingkid, 2015/07/08
- Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom, Laurent Vivier, 2015/07/08
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