From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42044) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e0aYY-000497-Ss for qemu-devel@nongnu.org; Fri, 06 Oct 2017 17:53:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e0aYU-0001ll-0c for qemu-devel@nongnu.org; Fri, 06 Oct 2017 17:53:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44024) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e0aYT-0001lL-OK for qemu-devel@nongnu.org; Fri, 06 Oct 2017 17:53:13 -0400 From: Eduardo Habkost Date: Fri, 6 Oct 2017 18:52:44 -0300 Message-Id: <20171006215244.27104-8-ehabkost@redhat.com> In-Reply-To: <20171006215244.27104-1-ehabkost@redhat.com> References: <20171006215244.27104-1-ehabkost@redhat.com> Subject: [Qemu-devel] [PATCH 7/7] target/i386: Enable kvm_pv_unhalt by default List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , "Michael S. Tsirkin" , Igor Mammedov , Alexander Graf Original description of a patch by Alexander Graf that did something similar: Commit f010bc643a (target-i386: add feature kvm_pv_unhalt) introduced the kvm_pv_unhalt feature but didn't enable it by default. Without kvm_pv_unhalt we see a measurable degradation in scheduling performance, so enabling it by default does make sense IMHO. This patch just flips it to default to on by default. [With kvm_pv_unhalt disabled] $ perf bench sched messaging -l 10000 Total time: 8.573 [sec] [With kvm_pv_unhalt enabled] $ perf bench sched messaging -l 10000 Total time: 4.416 [sec] This patch does the same as that patch, but using a kvm_auto_enable_pv_unhalt flag to keep compatibility on older machine-types. kvm_pv_unhalt support was added to Linux on v3.12 (Linux commit 6aef266c6e17b798a1740cf70cd34f90664740b3), so update the system requirements section in qemu-doc.texi accordingly. Suggested-by: Alexander Graf Cc: Alexander Graf Signed-off-by: Eduardo Habkost --- include/hw/i386/pc.h | 4 ++++ target/i386/cpu.h | 3 +++ target/i386/cpu.c | 7 +++++++ qemu-doc.texi | 2 +- 4 files changed, 15 insertions(+), 1 deletion(-) diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h index d2742dd0bc..19b42de224 100644 --- a/include/hw/i386/pc.h +++ b/include/hw/i386/pc.h @@ -375,6 +375,10 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *); .driver = TYPE_X86_CPU,\ .property = "x-hv-max-vps",\ .value = "0x40",\ + },{\ + .driver = TYPE_X86_CPU,\ + .property = "x-kvm-auto-enable-pv-unhalt",\ + .value = "off",\ }, #define PC_COMPAT_2_9 \ diff --git a/target/i386/cpu.h b/target/i386/cpu.h index 7e5bf86921..db1eecff00 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -1276,6 +1276,9 @@ struct X86CPU { /* KVM automatically enables kvm-pv-eoi if not explicitly disabled by user */ bool kvm_auto_enable_pv_eoi; + /* KVM automatically enables kvm-pv-unhalt if not explicitly disabled */ + bool kvm_auto_enable_pv_unhalt; + /* Number of physical address bits supported */ uint32_t phys_bits; diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 2160738a37..7461c2a25e 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -3515,6 +3515,11 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp) x86_cpu_expand_feature(cpu, FEAT_KVM, (1 << KVM_FEATURE_PV_EOI), (1 << KVM_FEATURE_PV_EOI)); } + + if (cpu->kvm_auto_enable_pv_unhalt) { + x86_cpu_expand_feature(cpu, FEAT_KVM, (1 << KVM_FEATURE_PV_UNHALT), + (1 << KVM_FEATURE_PV_UNHALT)); + } } /*TODO: Now cpu->max_features doesn't overwrite features @@ -4164,6 +4169,8 @@ static Property x86_cpu_properties[] = { X86CPU, kvm_auto_enable_x2apic, true), DEFINE_PROP_BOOL("x-kvm-auto-enable-pv-eoi", X86CPU, kvm_auto_enable_pv_eoi, true), + DEFINE_PROP_BOOL("x-kvm-auto-enable-pv-unhalt", + X86CPU, kvm_auto_enable_pv_unhalt, true), DEFINE_PROP_BOOL("vmware-cpuid-freq", X86CPU, vmware_cpuid_freq, true), DEFINE_PROP_BOOL("tcg-cpuid", X86CPU, expose_tcg, true), diff --git a/qemu-doc.texi b/qemu-doc.texi index be45b6b6f6..73c831383a 100644 --- a/qemu-doc.texi +++ b/qemu-doc.texi @@ -2355,7 +2355,7 @@ Run the emulation in single step mode. @section KVM kernel module On x86_64 hosts, the default set of CPU features enabled by the KVM accelerator -require the host to be running Linux v3.6 or newer. +require the host to be running Linux v3.12 or newer. @include qemu-tech.texi -- 2.13.6