On Fri, 02 Sep 2016 14:58:12 +0530
Nikunj A Dadhania <nik...@linux.vnet.ibm.com> wrote:
> Greg Kurz <gr...@kaod.org> writes:
>
> > On Fri, 2 Sep 2016 12:02:53 +0530
> > Nikunj A Dadhania <nik...@linux.vnet.ibm.com> wrote:
> >
> >> Signed-off-by: Nikunj A Dadhania <nik...@linux.vnet.ibm.com>
> >> ---
> >> hw/ppc/spapr_hcall.c | 11 +++++++++--
> >> 1 file changed, 9 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> >> index e5eca67..daea7a0 100644
> >> --- a/hw/ppc/spapr_hcall.c
> >> +++ b/hw/ppc/spapr_hcall.c
> >> @@ -1075,20 +1075,27 @@ target_ulong spapr_hypercall(PowerPCCPU *cpu,
> >> target_ulong opcode,
> >> target_ulong *args)
> >> {
> >> sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> >> + target_ulong ret;
> >>
> >> if ((opcode <= MAX_HCALL_OPCODE)
> >> && ((opcode & 0x3) == 0)) {
> >> spapr_hcall_fn fn = papr_hypercall_table[opcode / 4];
> >>
> >> if (fn) {
> >> - return fn(cpu, spapr, opcode, args);
> >> + qemu_mutex_lock_iothread();
> >> + ret = fn(cpu, spapr, opcode, args);
> >> + qemu_mutex_unlock_iothread();
> >> + return ret;
> >> }
> >> } else if ((opcode >= KVMPPC_HCALL_BASE) &&
> >> (opcode <= KVMPPC_HCALL_MAX)) {
> >> spapr_hcall_fn fn = kvmppc_hypercall_table[opcode -
> >> KVMPPC_HCALL_BASE];
> >>
> >> if (fn) {
> >> - return fn(cpu, spapr, opcode, args);
> >> + qemu_mutex_lock_iothread();
> >> + ret = fn(cpu, spapr, opcode, args);
> >> + qemu_mutex_unlock_iothread();
> >> + return ret;
> >> }
> >> }
> >>
> >
> > This will serialize all hypercalls, even when it is not needed... Isn't that
> > too much coarse grain locking ?
>
> You are right, I was thinking to do this only for emulation case, as
> this is not needed for hardware acceleration.
>
Yes, at the very least. And even in the MTTCG case, shouldn't we serialize only
when we know I/O will actually happen ?
> Regards
> Nikunj
>
>
Cheers.
--
Greg
