[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 00/13] Add VMX TSC scaling support
On 09/28/2015 06:51 AM, Andrew Cooper wrote: On 28/09/15 08:13, Haozhong Zhang wrote:This patchset adds support for VMX TSC scaling feature which is available on Intel Skylake CPU. The specification of VMX TSC scaling can be found at http://www.intel.com/content/www/us/en/processors/timestamp-counter-scaling-virtualization-white-paper.html VMX TSC scaling allows guest TSC which is read by guest rdtsc(p) instructions increases in a rate that is customized by the hypervisor and can be different than the host TSC rate. Basically, VMX TSC scaling adds a 64-bit field called TSC multiplier in VMCS so that, if VMX TSC scaling is enabled, TSC read by guest rdtsc(p) instructions will be calculated by the following formula: guest EDX:EAX = (Host TSC * TSC multiplier) >> 48 + VMX TSC Offset where, Host TSC = Host MSR_IA32_TSC + Host MSR_IA32_TSC_ADJUST. This patchset is composed of following four parts. 1. PATCH 01 - 02 fix bugs in tsc_get_info() which could result in errors when VMX TSC scaling is used.2. PATCH 03 - 09 add/move the common parts of VMX TSC scaling andSVM TSC ratio to hvm.c and x86/time.c.3. PATCH 10 - 12 implement the VMX-specific code for supporting VMXTSC scaling.4. PATCH 13 adapts libxl for VMX TSC scaling (as well as SVM TSCratio).Thankyou for this series. I have had a brief look over it and it appears to be in good shape, but have not done a thorough review yet. Konrad/Boris: As Oracle are the main users of the more interesting guest timing modes, do you have tests to verify correct functioning? Not really. The most interesting thing to test here I think would be migration between differently-clocked systems and we only do save/restore. -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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