Greg Kurz <gr...@kaod.org> writes:
> 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 ?
Yes, haven't figured out what all would need protection apart from I/O.
I have started with coarse grain locking and will start fine tuning,
once other issues are sorted out.
Regards,
Nikunj
