On 02/07/2015 15:47, Paolo Bonzini wrote:
>
>
> On 02/07/2015 14:24, Laurent Vivier wrote:
>>
>> #ifdef __FreeBSD__
>> if (S_ISCHR(st.st_mode)) {
>> /*
>> * The file is a char device (disk), which on FreeBSD isn't behind
>> * a pager, so force all requests to be aligned. This is needed
>> * so QEMU makes sure all IO operations on the device are aligned
>> * to sector size, or else FreeBSD will reject them with EINVAL.
>> */
>> s->needs_alignment = true;
>> }
>> #endif
>
> So on FreeBSD and Apple /dev/r* is the equivalent of BDRV_O_NO_CACHE?
This is what I understand (MacOS is a derivative from FreeBSD)
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/hdiutil.1.html
DEVICE SPECIAL FILES
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.
Laurent
