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Re: [RFC PATCH v2 3/3] hw/block/pflash: use memory_region_init_rom_devic
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [RFC PATCH v2 3/3] hw/block/pflash: use memory_region_init_rom_device_from_file() |
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Date: |
Tue, 2 Mar 2021 10:54:11 +0000 |
On Tue, Mar 02, 2021 at 08:04:46AM +0100, Philippe Mathieu-Daudé wrote:
> On 3/1/21 7:13 PM, Stefan Hajnoczi wrote:
> > On Mon, Mar 01, 2021 at 12:53:29PM +0100, Philippe Mathieu-Daudé wrote:
> > FWIW this API isn't perfect because the file could be reopened with QMP
> > and the existing mmap would remain in place.
>
> Can you show me a QMP example or point me at the command?
x-blockdev-change and other commands can reopen or reconfigure the
BlockDriverState graph - the mmap user would not be aware of this.
For example, block_set_io_throttle won't take effect if the guest has
the device mmapped.
> This shouldn't happen with the pflash.
It's not possible to say that because pflash has a
DEFINE_PROP_DRIVE("drive") property. The storage is backed by a
--drive/--blockdev and the user could send any QMP command that operates
on drives :(.
Users probably won't but there is nothing stopping them.
The block layer has a permission system (BLK_PERM_*). Maybe it's
possible to use it to lock a BDS while mmap is active?
Stefan
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