From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:56978) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7QPT-0008P6-Id for qemu-devel@nongnu.org; Tue, 13 Mar 2012 08:01:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S7QP1-0004GV-67 for qemu-devel@nongnu.org; Tue, 13 Mar 2012 08:00:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14819) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7QP0-0004GF-JB for qemu-devel@nongnu.org; Tue, 13 Mar 2012 08:00:30 -0400 Message-ID: <4F5F36D8.9050800@redhat.com> Date: Tue, 13 Mar 2012 20:00:24 +0800 From: Amos Kong MIME-Version: 1.0 References: <20120313103602.8741.71939.stgit@dhcp-8-167.nay.redhat.com> <20120313104232.8741.89133.stgit@dhcp-8-167.nay.redhat.com> <4F5F34A2.6070301@siemens.com> In-Reply-To: <4F5F34A2.6070301@siemens.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/2] return available ioeventfds count in kvm_has_many_ioeventfds() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: aliguori@us.ibm.com, stefanha@linux.vnet.ibm.com, kvm@vger.kernel.org, mtosatti@redhat.com, qemu-devel@nongnu.org, avi@redhat.com On 13/03/12 19:50, Jan Kiszka wrote: > Please tag uq/master patches with "PATCH uq/master". > > On 2012-03-13 11:42, Amos Kong wrote: >> Older kernels have a 6 device limit on the KVM io bus. >> This patch makes kvm_has_many_ioeventfds() return available >> ioeventfd count. ioeventfd will be disabled if there is >> no 7 available ioeventfds. >> >> Signed-off-by: Amos Kong >> --- >> hw/virtio-pci.c | 2 +- >> kvm-all.c | 9 +++------ >> 2 files changed, 4 insertions(+), 7 deletions(-) >> >> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c >> index a0fb7c1..d63f303 100644 >> --- a/hw/virtio-pci.c >> +++ b/hw/virtio-pci.c >> @@ -678,7 +678,7 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev) >> pci_register_bar(&proxy->pci_dev, 0, PCI_BASE_ADDRESS_SPACE_IO, >> &proxy->bar); >> >> - if (!kvm_has_many_ioeventfds()) { >> + if (kvm_has_many_ioeventfds() != 7) { >> proxy->flags&= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD; >> } >> >> diff --git a/kvm-all.c b/kvm-all.c >> index 3c6b4f0..d12694b 100644 >> --- a/kvm-all.c >> +++ b/kvm-all.c >> @@ -78,7 +78,6 @@ struct KVMState >> int pit_in_kernel; >> int pit_state2; >> int xsave, xcrs; >> - int many_ioeventfds; >> int irqchip_inject_ioctl; >> #ifdef KVM_CAP_IRQ_ROUTING >> struct kvm_irq_routing *irq_routes; >> @@ -510,8 +509,8 @@ static int kvm_check_many_ioeventfds(void) >> } >> } >> >> - /* Decide whether many devices are supported or not */ >> - ret = i == ARRAY_SIZE(ioeventfds); >> + /* If i equals to 7, many devices are supported */ >> + ret = i; >> >> while (i--> 0) { >> kvm_set_ioeventfd_pio_word(ioeventfds[i], 0, i, false); >> @@ -1078,8 +1077,6 @@ int kvm_init(void) >> kvm_state = s; >> memory_listener_register(&kvm_memory_listener, NULL); >> >> - s->many_ioeventfds = kvm_check_many_ioeventfds(); >> - >> cpu_interrupt_handler = kvm_handle_interrupt; >> >> return 0; >> @@ -1407,7 +1404,7 @@ int kvm_has_many_ioeventfds(void) >> if (!kvm_enabled()) { >> return 0; >> } >> - return kvm_state->many_ioeventfds; >> + return kvm_check_many_ioeventfds(); > > And why are you dropping the caching of the kvm_check_many_ioeventfds() > return value? Is kvm_has_many_ioeventfds not used outside init scopes? Hi Jan, In the past, kvm_state->many_ioeventfds is only updated once at the beginning, I want to use kvm_check_many_ioeventfds() to check if available ioeventfd exists before starting ioeventfd each time. -- Amos.