Re: [Qemu-devel] [PATCH 4/5] target/arm: Fill in ARMISARegisters for kvm32

[Peter Maydell]

On 29 October 2018 at 15:13, Peter Maydell <address@hidden> wrote:
> On 24 October 2018 at 12:37, Richard Henderson
> <address@hidden> wrote:
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>  target/arm/kvm32.c | 33 ++++++++++++++++++++++++++++-----
>>  1 file changed, 28 insertions(+), 5 deletions(-)
>
> Reviewed-by: Peter Maydell <address@hidden>
>
>> +    /*
>> +     * FIXME: There is not yet a way to read MVFR2.
>> +     * Fortunately there is not yet anything in there that affects 
>> migration.
>> +     */
>
> We should bring that up with the KVM folks (cc'd)...
>
> Presumably KVM_REG_ARM_VFP_MVFR2 should be 0x1005 and the code
> in the kernel for handling this bit of the get/set-one-reg
> ioctls needs to have code for it (including returning 0
> for v7 CPUs, where this VMRS register encoding was UNPREDICTABLE).

There's an argument for "fail the ioctl on v7 CPUs" rather than
"return 0"; I don't think I have a strong opinion, since in
practice userspace needs to handle the "doesn't exist" case
when it's running on an older kernel anyway.

thanks
-- PMM