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Re: [Qemu-devel] [PATCH v2 0/3] x86-kvm: Fix Mac guest timekeeping by ex
Re: [Qemu-devel] [PATCH v2 0/3] x86-kvm: Fix Mac guest timekeeping by exposing TSC frequency in CPUID
Tue, 24 Jan 2017 12:58:34 +0100
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1
On 20/01/2017 15:11, Phil Dennis-Jordan wrote:
> Darwin/OS X/macOS for x86-64 uses the TSC for timekeeping; it normally
> calibrates this by querying various clock frequency scaling MSRs. Details
> depend on the exact CPU model detected. The local APIC timer frequency is
> extracted from (EFI) firmware. Virtualisation environments including Qemu/KVM
> don't expose those MSRs to guests, and in any case the host and guest CPUs'
> MSRs may not match up. To solve this, the xnu kernel queries CPUID leaf
> 0x40000010 for the TSC and APIC timers if leaf 0x40000000 suggests that this
> leaf exists, which is the case when running inside VMWare (Fusion). This
> patch series replicates the behaviour of these CPUID leaves for Qemu/KVM via
> a new x86 CPU option, "vmware-cpuid-freq."
> The option is activated by default on 2.9 and newer pc (PIIX and Q35) machine
> variants, if the TSC is stable and known (invtsc or user-specified).
> v1 -> v2
> * The v1 thread was "[PATCH] x86-KVM: Supply TSC and APIC clock rates to
> guest like VMWare"
> * The option has been renamed as suggested in the v1 discussion.
> * It now checks that either invtsc or a user-specified TSC clock rate are
> active before activating leaf 0x40000010.
> * CPUID leaf 0x40000000 exposed by KVM will only reference 0x40000010 if all
> preconditions are met and the functionality is actually active.
> * No more error message if preconditions are not met.
> * cpuid_data.cpuid.nent update/cpuid_find_entry bug fixed.
> * 2 extra patches included, one for setting up PC machine version 2.8/2.9
> compatibility configurations, the second for enabling the new option in
> version 2.9+ PIIX/q35 configurations by default, while leaving it disabled
> for 2.8 or older machines.
> Phil Dennis-Jordan (3):
> x86-KVM: Supply TSC and APIC clock rates to guest like VMWare
> pc: Add 2.9 machine type
> pc: Enable vmware-cpuid-freq CPU option for 2.9+ machine types
> hw/i386/pc_piix.c | 13 ++++++++++++-
> hw/i386/pc_q35.c | 12 +++++++++++-
> include/hw/i386/pc.h | 6 ++++++
> target/i386/cpu.c | 1 +
> target/i386/cpu.h | 4 ++++
> target/i386/kvm.c | 36 ++++++++++++++++++++++++++++++------
> 6 files changed, 64 insertions(+), 8 deletions(-)
Looks good, thanks! Queued patches 1 and 3 for 2.9 (patch 2 is in already).