[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] RE: Saving/Restoring IA32_TSC_AUX MSR
Hi Jun -- Xen doesn't expose the TSC rdtscp bit so assumes that no guests depend on it. So no save/restore of TSC_AUX is necessary. Xen could provide support for the TSC rdtscp bit and allow a guest OS to manage TSC_AUX, but the existing use of TSC_AUX by Linux would fail to provide the desired result across migration, so there's little point. Also the pvrdtscp algorithm now assumes that Xen itself is responsible for updating TSC_AUX whenever a migration (across physical machines) occurs. The #define for write_rdtscp_aux is from Linux source, so I didn't change the code and define the constant. Dan > -----Original Message----- > From: Nakajima, Jun [mailto:jun.nakajima@xxxxxxxxx] > Sent: Wednesday, December 09, 2009 9:42 AM > To: xen-devel@xxxxxxxxxxxxxxxxxxx > Cc: Dan Magenheimer > Subject: Saving/Restoring IA32_TSC_AUX MSR > > > I see the code like (in arch/x86/time.c), and wondering how > IA32_TSC_AUX MSR is saved/restored at domain switch time. > > if ( (d->arch.tsc_mode == TSC_MODE_PVRDTSCP) && > boot_cpu_has(X86_FEATURE_RDTSCP) ) > write_rdtscp_aux(d->arch.incarnation); > > BTW, > > include/asm-x86/msr.h > #define write_rdtscp_aux(val) wrmsr(0xc0000103, (val), 0) > > We should write like wrmsr(MSR_TSC_AUX, (val), 0) by adding > +#define MSR_TSC_AUX 0xc0000103 /* Auxiliary TSC */ > in include/asm-x86/msr-index.h > > Thanks, > Jun > --- > Intel Open Source Technology Center > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |