Re: [Qemu-devel] [PATCH] i386/kvm: Fix build with -m32

[Max Reitz <mreitz@redhat.com>]

On 24.06.19 21:26, Max Reitz wrote:
> On 24.06.19 21:21, Eduardo Habkost wrote:
>> On Mon, Jun 24, 2019 at 09:02:14PM +0200, Max Reitz wrote:
>>> find_next_bit() takes a pointer of type "const unsigned long *", but the
>>> first argument passed here is a "uint64_t *".  These types are
>>> incompatible when compiling qemu with -m32.
>>>
>>> Just cast it to "const void *", find_next_bit() works fine with any type
>>> on little-endian hosts (which x86 is).
>>>
>>> Fixes: c686193072a47032d83cb4e131dc49ae30f9e5d
>>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>>
>> Why not declare kvm_hyperv_properties.dependencies with the right
>> type for bitmaps, using
>>   unsigned long dependencies[BITS_TO_LONGS(64)]
>> ?
> 
> How would you (statically) initialize that field, then?
> 
> I cannot imagine a reasonable static way that does not invoke the same
> “The host must be little-endian, so it’s OK” assumption.

Sorry, brain fart.  That’s not the problem because in either case, the
lower index will receive the lower-indexed bits.

But we’d still have to deal with the fact that it could either be one or
two indices, which doesn’t seem nice to initialize either.

Max

> The better question is perhaps, why not use ffsll().  Hm.  I don’t know,
> maybe I should?
> 
> Max
>