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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 22:03:07 +0530 |
User-agent: |
Notmuch/0.21 (https://notmuchmail.org) Emacs/25.0.94.1 (x86_64-redhat-linux-gnu) |
Thomas Huth <address@hidden> writes:
> On 02.09.2016 08:32, Nikunj A Dadhania 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;
>> }
>> }
>
> I think this will cause a deadlock when running on KVM since the lock is
> already taken in kvm_arch_handle_exit() - which calls spapr_hypercall()!
Ouch, havent tried this branch yet on KVM :(
Will change to emulation only as suggested in my previous mails.
Regards,
Nikunj