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Re: [Qemu-ppc] [Qemu-devel] [PATCH RFC 1/4] spapr-hcall: take iothread l
From: |
Nikunj A Dadhania |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH RFC 1/4] spapr-hcall: take iothread lock during handler call |
Date: |
Sat, 03 Sep 2016 22:01:18 +0530 |
User-agent: |
Notmuch/0.21 (https://notmuchmail.org) Emacs/25.0.94.1 (x86_64-redhat-linux-gnu) |
Greg Kurz <address@hidden> writes:
> On Fri, 02 Sep 2016 14:58:12 +0530
> Nikunj A Dadhania <address@hidden> wrote:
>
>> Greg Kurz <address@hidden> writes:
>>
>> > On Fri, 2 Sep 2016 12:02:53 +0530
>> > Nikunj A Dadhania <address@hidden> wrote:
>> >
>> >> Signed-off-by: Nikunj A Dadhania <address@hidden>
>> >> ---
>> >> 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
[Qemu-ppc] [PATCH RFC 2/4] target-ppc: with MTTCG report more threads, Nikunj A Dadhania, 2016/09/02
Re: [Qemu-ppc] [PATCH RFC 2/4] target-ppc: with MTTCG report more threads, David Gibson, 2016/09/07
[Qemu-ppc] [PATCH RFC 4/4] target-ppc: flush tlb from all the cpu, Nikunj A Dadhania, 2016/09/02