On 06/11/2015 13:42, Haozhong Zhang wrote: > On 11/06/15 11:49, Paolo Bonzini wrote: >> >> >> On 20/10/2015 09:39, 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, when cooperating with another QEMU patchset (sent in >>> another email "target-i386: save/restore vcpu's TSC rate during >>> migration"), allows guest programs observe a consistent TSC rate even >>> though they are migrated among machines with different host TSC rates. >>> >>> VMX TSC scaling shares some common logics with SVM TSC ratio which >>> is already supported by KVM. Patch 1 ~ 8 move those common logics from >>> SVM code to the common code. Upon them, patch 9 ~ 12 add VMX-specific >>> support for VMX TSC scaling. >>> >>> Changes in v2: >>> * Remove the duplicated variable 'kvm_tsc_scaling_ratio_rsvd'. >>> * Remove an unnecessary error check in original patch 2. >>> * Do 64-bit arithmetic by functions recommended by Paolo. >>> * Make kvm_set_tsc_khz() returns an error number so that ioctl >>> KVM_SET_TSC_KHZ does not return 0 if errors happen. >>> >>> Reviewed-by: Eric Northup <digitaleric@xxxxxxxxxx> >> >> Thanks for the patches. There are a couple changes that I can do myself: >> >> 1) kvm_default_tsc_scaling_ratio can be initialized in >> kvm_arch_hardware_setup, since it's just 1ULL << >> kvm_tsc_scaling_ratio_frac_bits >> > Agree > >> 2) things that you are adding to include/linux/kvm_host.h should instead >> go in arch/x86/include/linux/kvm_host.h >> > Agree, because they are x86 specific. > >> That's it. I'll commit it as soon as I test on AMD (today hopefully). It tested fine. I'll give it a shot with the 32-bit mul_u64_u64_shr on Monday as well, but I don't expect any issue. Thanks, the patches are neat! Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
