From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45962) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bflNN-0007GK-Eu for qemu-devel@nongnu.org; Fri, 02 Sep 2016 06:07:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bflNH-0007Ka-EJ for qemu-devel@nongnu.org; Fri, 02 Sep 2016 06:07:08 -0400 References: <1472797976-24210-1-git-send-email-nikunj@linux.vnet.ibm.com> <1472797976-24210-2-git-send-email-nikunj@linux.vnet.ibm.com> From: Thomas Huth Message-ID: <73c88737-b7ca-47f2-ccdf-0d0a030da3f0@redhat.com> Date: Fri, 2 Sep 2016 12:06:56 +0200 MIME-Version: 1.0 In-Reply-To: <1472797976-24210-2-git-send-email-nikunj@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC 1/4] spapr-hcall: take iothread lock during handler call List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikunj A Dadhania , qemu-ppc@nongnu.org, alex.bennee@linaro.org, david@gibson.dropbear.id.au, rth@twiddle.net Cc: qemu-devel@nongnu.org On 02.09.2016 08:32, Nikunj A Dadhania wrote: > Signed-off-by: Nikunj A Dadhania > --- > 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()! Thomas