run_qemu.sh: fix --rw option just broken by switch to -blockdev #213
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Use a qcow2 overlay to fix the --rw regression just added by commit dfa1d3f ("run_qemu.sh: replace -drive rootfs with -blockdev + -device") The QEMU -snapshot option is silently ignored by -blockdev (this is documented in the qemu-system man page) Signed-off-by: Marc Herbert <[email protected]>
| @@ -1903,6 +1914,7 @@ prepare_qcmd() | |||
| fi | |||
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| if [[ $_arg_rw == "off" ]]; then | |||
| # Note this is only for the (deprecated) -drive and ignored by -blockdev | |||
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Does it make sense to just remove this block - considering we've fully moved away from -drive..
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We still use -drive in a couple other places.
| else | ||
| local _overlay=${_arg_rootfs}-overlay.qcow2 | ||
| rm -f "${_overlay}" | ||
| qemu-img create -F raw -b "${_arg_rootfs}" -f qcow2 "${_overlay}" |
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Just out of curiosity, is there a way to 'apply' the overlay onto the raw image?
A workflow I've used in the past is to create an image using run_qemu with my kernel and anything else I need, and then use that raw image elsewhere, say an emulator or even dd it to a drive and use it on a real system. I'm not sure if something like this is frequently used/needed by others, but these changes (starting with -blockdev) would preclude doing this..
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is there a way to 'apply' the overlay onto the raw image?
You can "apply" and many other things using qemu-img but I think that's out of scope for run_qemu.sh. I mean, run_qemu.sh is already a wrapper of many other tools, I don't think we should add qemu-img to that long list.
The overlay is left behind (until the next run) so anyone is free to change their mind and apply it outside run_qemu.sh.
but these changes (starting with -blockdev) would preclude doing this..
This PR is designed to fix --rw which I just broke and bring it back exactly where it was. I don't see what it would preclude, can you elaborate? If nothing else I feel like it's opening more possibilities, including... becoming a qemu-img wrapper, which I think is not a good idea.
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Oh yes I was not suggesting run_qemu should grow to provide this apply overlay functionality. More that if we ever wanted to do this kind of an "export a customized image" workflow, there was still /some/ way to accomplish that with the overlay. No issues merging this by me!
| else | ||
| local _overlay=${_arg_rootfs}-overlay.qcow2 | ||
| rm -f "${_overlay}" | ||
| qemu-img create -F raw -b "${_arg_rootfs}" -f qcow2 "${_overlay}" |
There was a problem hiding this comment.
is there a way to 'apply' the overlay onto the raw image?
You can "apply" and many other things using qemu-img but I think that's out of scope for run_qemu.sh. I mean, run_qemu.sh is already a wrapper of many other tools, I don't think we should add qemu-img to that long list.
The overlay is left behind (until the next run) so anyone is free to change their mind and apply it outside run_qemu.sh.
but these changes (starting with -blockdev) would preclude doing this..
This PR is designed to fix --rw which I just broke and bring it back exactly where it was. I don't see what it would preclude, can you elaborate? If nothing else I feel like it's opening more possibilities, including... becoming a qemu-img wrapper, which I think is not a good idea.
| @@ -1903,6 +1914,7 @@ prepare_qcmd() | |||
| fi | |||
|
|
|||
| if [[ $_arg_rw == "off" ]]; then | |||
| # Note this is only for the (deprecated) -drive and ignored by -blockdev | |||
There was a problem hiding this comment.
We still use -drive in a couple other places.
Use a qcow2 overlay to fix the --rw regression just added by commit dfa1d3f ("run_qemu.sh: replace -drive rootfs with -blockdev + -device")
The QEMU -snapshot option is silently ignored by -blockdev (this is documented in the qemu-system man page)