From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=35014 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pjwoj-0007tQ-GM for qemu-devel@nongnu.org; Mon, 31 Jan 2011 11:41:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pjwoh-0007ua-SO for qemu-devel@nongnu.org; Mon, 31 Jan 2011 11:41:29 -0500 Received: from goliath.siemens.de ([192.35.17.28]:24665) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pjwoh-0007tw-Jo for qemu-devel@nongnu.org; Mon, 31 Jan 2011 11:41:27 -0500 Message-ID: <4D46E634.30109@siemens.com> Date: Mon, 31 Jan 2011 17:41:24 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <8db93a26b3cbb67e309d05600811dd6a37b34433.1296133797.git.jan.kiszka@siemens.com> <4D468A24.4080800@redhat.com> <4D469ED6.9050805@siemens.com> <4D46B369.3050404@siemens.com> <4D46D7F2.3040502@siemens.com> <20110131163858.GA18827@redhat.com> In-Reply-To: <20110131163858.GA18827@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH 17/22] kvm: Move irqchip event processing out of inner loop List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Marcelo Tosatti , Avi Kivity , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" On 2011-01-31 17:38, Gleb Natapov wrote: > On Mon, Jan 31, 2011 at 04:40:34PM +0100, Jan Kiszka wrote: >> On 2011-01-31 14:04, Jan Kiszka wrote: >>> On 2011-01-31 12:36, Jan Kiszka wrote: >>>> On 2011-01-31 11:08, Avi Kivity wrote: >>>>> On 01/27/2011 03:10 PM, Jan Kiszka wrote: >>>>>> Align with qemu-kvm and prepare for IO exit fix: There is no need to run >>>>>> kvm_arch_process_irqchip_events in the inner VCPU loop. Any state change >>>>>> this service processes will first cause an exit from kvm_cpu_exec >>>>>> anyway. And we will have to reenter the kernel on IO exits >>>>>> unconditionally, something that the current logic prevents. >>>>>> >>>>>> Signed-off-by: Jan Kiszka >>>>>> --- >>>>>> kvm-all.c | 11 ++++++----- >>>>>> 1 files changed, 6 insertions(+), 5 deletions(-) >>>>>> >>>>>> diff --git a/kvm-all.c b/kvm-all.c >>>>>> index 5bfa8c0..46ecc1c 100644 >>>>>> --- a/kvm-all.c >>>>>> +++ b/kvm-all.c >>>>>> @@ -892,6 +892,12 @@ int kvm_cpu_exec(CPUState *env) >>>>>> >>>>>> DPRINTF("kvm_cpu_exec()\n"); >>>>>> >>>>>> + if (kvm_arch_process_irqchip_events(env)) { >>>>>> + env->exit_request = 0; >>>>>> + env->exception_index = EXCP_HLT; >>>>>> + return 0; >>>>>> + } >>>>>> + >>>>>> do { >>>>>> #ifndef CONFIG_IOTHREAD >>>>>> if (env->exit_request) { >>>>>> @@ -901,11 +907,6 @@ int kvm_cpu_exec(CPUState *env) >>>>>> } >>>>> >>>>> We check for ->exit_request here >>>>> >>>>>> #endif >>>>>> >>>>>> - if (kvm_arch_process_irqchip_events(env)) { >>>>>> - ret = 0; >>>>>> - break; >>>>>> - } >>>>>> - >>>>> >>>>> But this checks for ->interrupt_request. What ensures that we exit when >>>>> ->interrupt_request is set? >>>> >>>> Good question, need to check again. But if that turns out to be an >>>> issue, qemu-kvm would be broken as well. I'm just aligning the code here. >>>> >>> >>> The only thing we miss by moving process_irqchip_events is a self-INIT >>> of an AP - if such thing exists in real life. In that case, the AP would >>> cause a reset of itself, followed by a transition to HALT state. >> >> I checked again with the Intel spec, and a self-INIT is invalid (at >> least when specified via shorthand). So I'm under the impression now >> that we can safely ignore this case and leave the patch as is. >> >> Any different views? >> > IIRC if you don't use shorthand you can send INIT to self. We didn't care so far (in qemu-kvm), do you think we should? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux