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[Qemu-devel] ivshmem property size should be a size, not a string
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] ivshmem property size should be a size, not a string |
Date: |
Fri, 20 Nov 2015 17:07:08 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Everybody's favourite device model has "size" property. It's declared
as *string*
DEFINE_PROP_STRING("size", IVShmemState, sizearg),
which gets converted to a size manually in the realize method:
} else if (s->sizearg == NULL) {
s->ivshmem_size = 4 << 20; /* 4 MB default */
} else {
char *end;
int64_t size = qemu_strtosz(s->sizearg, &end);
if (size < 0 || *end != '\0' || !is_power_of_2(size)) {
error_setg(errp, "Invalid size %s", s->sizearg);
return;
}
s->ivshmem_size = size;
}
This is *wrong*. Impact, as far as I can tell:
* -device ivshmem,help shows the property as 'str' instead of 'size'.
Unhelpful, but hardly show-stopper.
* On the command line and in HMP, ivshmem's size is parsed differently
than other size properties. In particular, a number without a suffix
is normally interpreted as bytes, except for ivshmem, where it's
Mebibytes.
Ugly inconsistency, but hardly the only one.
* In QMP, the size must be given as JSON string instead of JSON number,
and size suffixes are accepted. Example: "size": "512k" instead of
"size": 524288.
Right now, this violation of QMP rules is tolerable (barely), because
device_add breaks some of these rules already. However, one goal of
the current work on QAPI is to support a QMP command to plug devices
that doesn't break QMP rules, and then this violation will stand out.
Therefore, I want it fixed now, before ivshmem gets used in anger.
A straight fix of size isn't fully backwards compatible: suffixes no
longer work in QMP, and you need to use an 'M' suffix to get Mebibytes
on command line and HMP.
If that's unacceptable, we'll have to provide a new, fixed property,
and deprecate size.
Opinions?
- [Qemu-devel] ivshmem property size should be a size, not a string,
Markus Armbruster <=
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Marc-André Lureau, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Eric Blake, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Markus Armbruster, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Marc-André Lureau, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Markus Armbruster, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Marc-André Lureau, 2015/11/20
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Markus Armbruster, 2015/11/23
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Marc-André Lureau, 2015/11/23
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Markus Armbruster, 2015/11/23
- Re: [Qemu-devel] ivshmem property size should be a size, not a string, Marc-André Lureau, 2015/11/23