Re: [PATCH 2/3] qemu-x86: Add tsc_freq option to -cpu

Joerg Roedel
2011-07-19T13:30:05Z

On Tue, Jul 19, 2011 at 03:20:37PM +0300, Avi Kivity wrote:
> On 07/19/2011 02:46 PM, Marcelo Tosatti wrote:
>> On Thu, Jul 07, 2011 at 04:13:12PM +0200, Joerg Roedel wrote:
>> > To let the user configure the desired tsc frequency for the
>> > guest if running in KVM.
>> >
>> > Signed-off-by: Joerg Roedel<joerg.roedel@amd.com>
>> > ---
>> > target-i386/cpu.h | 1 +
>> > target-i386/cpuid.c | 13 +++++++++++++
>> > 2 files changed, 14 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/target-i386/cpu.h b/target-i386/cpu.h
>> > index cdf68ff..399e124 100644
>> > --- a/target-i386/cpu.h
>> > +++ b/target-i386/cpu.h
>> > @@ -743,6 +743,7 @@ typedef struct CPUX86State {
>> > uint32_t cpuid_kvm_features;
>> > uint32_t cpuid_svm_features;
>> > bool tsc_valid;
>> > + int tsc_khz;
>>
>> This should be saved/restore in migration data (missing VMSTATE entry).
>
> Why? It's static data. Traditionally we only migrate runtime data.
>
> (although we've been talking about starting a naked qemu and pushing all
> of the configuration from the source).

Hmm, I planned to do the VMSTATE thing in a follow-on patch-set. The
plan is to read the VCPU tsc_freq at guest start time on !tsc-scale
hosts and migrate it over so that the destination host can set the
tsc-freq if it supports tsc-scaling.

Joerg