From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56146 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PjtR0-0005Jo-IX for qemu-devel@nongnu.org; Mon, 31 Jan 2011 08:04:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PjtQz-0001Qf-5G for qemu-devel@nongnu.org; Mon, 31 Jan 2011 08:04:46 -0500 Received: from goliath.siemens.de ([192.35.17.28]:17310) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PjtQy-0001QA-OH for qemu-devel@nongnu.org; Mon, 31 Jan 2011 08:04:45 -0500 Message-ID: <4D46B369.3050404@siemens.com> Date: Mon, 31 Jan 2011 14:04:41 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <8db93a26b3cbb67e309d05600811dd6a37b34433.1296133797.git.jan.kiszka@siemens.com> <4D468A24.4080800@redhat.com> <4D469ED6.9050805@siemens.com> In-Reply-To: <4D469ED6.9050805@siemens.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: Avi Kivity Cc: Marcelo Tosatti , "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" 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. A self-SIPI has no effect as A) a CPU can't send a SIPI from wait-on-SIPI state and B) SIPIs are ignored in any other state. Will post a version that additionally checks for pending INIT as well and injects a self-ipi then. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux