Messages in this thread | | | Date | Wed, 16 Nov 2022 18:04:37 +0200 | From | Andy Shevchenko <> | Subject | Re: [PATCH v4 1/1] virt: acrn: Mark the uuid field as unused |
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On Wed, Nov 16, 2022 at 04:20:08PM +0100, Greg Kroah-Hartman wrote: > On Wed, Nov 16, 2022 at 03:29:31PM +0200, Andy Shevchenko wrote: > > On Wed, Nov 16, 2022 at 12:42:16PM +0100, Greg Kroah-Hartman wrote: > > > On Wed, Nov 16, 2022 at 11:22:54AM +0200, Andy Shevchenko wrote:
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> > > > - * @uuid: UUID of the VM. Pass to hypervisor directly. > > > > + * @uuid: Reserved (used to be UUID of the VM) > > > > > > If it's reserved, then don't you need to check for 0? > > > > Reserved in a way that it may content something we just don't care about. > > "reserved" in the kernel ioctls mean "must be 0 and we will test for it, > otherwise this is an empty/useless field that can never be touched again > in the future. > > Please spell it out in detail as to if you can ever use this later on, > and what the kernel will do (if anything) if it is set. > > And if "the kernel ignores it" then that means these bytes are now > "empty space never to be used again", right?
Right, I will fix this in v5.
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> > > > + __u8 uuid[16]; > > > > > > You just changed the type here, so what is that going to break in > > > userspace that depended on this being of a structure type and now it's > > > an array? > > > > It's the same. The previous was hidden behind additional type level. > > Same size, yes. Same C structure definition, no.
It doesn't matter, see below.
> > > And no other kernel changes needed? Shouldn't you warn if this field is > > > set? > > > > No, as pointed out in the commit message kernel never ever used this. > > That does not mean that userspace tools never did, right? You are > changing the structure definition, what tool just broke?
The only tool has been amended like a year ago, so the answer is none. The commit message has links to the commits in question that made that amendment.
Maybe I should remove Fixes tags? In such case we will very much know that no old tools will be run on the new kernel.
-- With Best Regards, Andy Shevchenko
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