Date: Mon, 16 Mar 2015 11:57:04 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r280134 - head/sys/amd64/vmm Message-ID: <201503161157.t2GBv4YJ069380@svn.freebsd.org>
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Author: mav Date: Mon Mar 16 11:57:03 2015 New Revision: 280134 URL: https://svnweb.freebsd.org/changeset/base/280134 Log: Report ARAT (APIC-Timer-always-running) feature for virtual CPU. This makes FreeBSD guest to not avoid using LAPIC timer, preferring HPET due to worries about non-existing for virtual CPUs deep sleep states. Benchmarks of usleep(1) on guest and host show such extra latencies: - 51us for virtual HPET, - 22us for virtual LAPIC timer, - 22us for host HPET and - 3us for host LAPIC timer. MFC after: 2 weeks Modified: head/sys/amd64/vmm/x86.c Modified: head/sys/amd64/vmm/x86.c ============================================================================== --- head/sys/amd64/vmm/x86.c Mon Mar 16 09:15:59 2015 (r280133) +++ head/sys/amd64/vmm/x86.c Mon Mar 16 11:57:03 2015 (r280134) @@ -361,6 +361,12 @@ x86_emulate_cpuid(struct vm *vm, int vcp break; case CPUID_0000_0006: + regs[0] = CPUTPM1_ARAT; + regs[1] = 0; + regs[2] = 0; + regs[3] = 0; + break; + case CPUID_0000_000A: /* * Handle the access, but report 0 for
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