Re: [Qemu-devel] [Android-virt] plans for QEMU support for KVM on ARM

[Peter Maydell]

On 22 November 2011 15:05, Alexander Graf <address@hidden> wrote:
> On 22.11.2011, at 15:44, Peter Maydell <address@hidden> wrote:
>> We're aiming for a reasonable working prototype of A15 guest on
>> an A15 Fast Model host here; we need to fix at least some of
>> the bugs which currently mean upstream QEMU doesn't work on ARM hosts,
>
> I thought there was upstream tcg support for arm now? What specifically
> doesn't work?

 * coroutine implementation doesn't cope if libc provides a makecontext()
   that returns ENOSYS (so we abort on startup)
 * the MAP_FIXED static codegen buffer is put at an address which overlaps
   the glibc heap so we crash about 50% of the time
 * if you try to start a standard i386 debian image which works fine on
   x86 host, the guest reboots just before displaying the blue-background
   grub image -- clearly something wrong here, not tracked down what yet
 * if the C code was compiled -mthumb, our choice of TCG_AREG0 clashes
   with the frame pointer (trivial fix but could do with a quick benchmark
   run to see whether making AREG0 r6 or r10 (ie thumb lowreg or high)
   has any effect on performance)

Those are just the ones I know about... The coroutine one is the only
one that KVM specifically will require a fix for, but being able to
cross-compare "run with KVM" vs "run with TCG" will be handy for
debugging I suspect.

ARM host support is documented as "known not to work" in the 1.0
release notes (see earlier mail to qemu-devel).

-- PMM