Re: [Qemu-arm] [PATCH for-4.0?] arm: Allow system registers for KVM guests to be changed by QEMU code

[Peter Maydell]

On Mon, 25 Mar 2019 at 10:25, Peter Maydell <address@hidden> wrote:
>
> On Mon, 18 Mar 2019 at 15:59, Alex Bennée <address@hidden> wrote:
> >
> >
> > Peter Maydell <address@hidden> writes:
[...]
> > > Support this by making kvm_arch_put_registers() synchronize
> > > CPU state back into the list. We sync only those registers
> > > where the initial write succeeds, which should be sufficient.
> > >
> > > This commit is the same as commit 823e1b3818f9b10b824ddc which we
> > > had to revert in commit 942f99c825fc94c8b1a4, except that the bug
> > > which was preventing EDK2 guest firmware running has been fixed:
> > > kvm_arm_reset_vcpu() now calls write_list_to_cpustate().

> > > Should we try to put this in for rc1? Not sure... Testing
> > > definitely appreciated.
>
> > Hmm so running my testcase:
> >
> >  * gdbstub enabled with an active sw or hw breakpoint
> >  * run userspace program in guest:
> >    - sw breakpoint works fine
> >    - hw breakpoint never triggers because guest segs
>
> Further testing from Alex suggests this is some unrelated
> bug or regression (ie not caused by this patch), but:
> since the only in-tree use for this patch is to get nested
> debugging working and it would be broken for this other
> reason even with this patch, I'm going to postpone applying
> this patch until the start of the 4.1 cycle.

Since we're now in the 4.1 cycle I'm going to apply this
patch, as I suggested above -- I'm putting it into my
target-arm.next queue to go in in my next pullreq.

We should make sure we investigate the debugging-KVM
breakage Alex described at some point this cycle too.

thanks
-- PMM