"Michael Kelley (EOSG)" <Michael.H.Kelley@xxxxxxxxxxxxx> writes: > On Fri, Dec 08, 2017 at 11:49:57AM +0100, Vitaly Kuznetsov wrote: > >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] >> Sent: Friday, December 8, 2017 2:50 AM >> To: kvm@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx >> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>; Radim Krčmář <rkrcmar@xxxxxxxxxx>; Thomas >> Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; H. Peter Anvin >> <hpa@xxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang >> <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; Michael >> Kelley (EOSG) <Michael.H.Kelley@xxxxxxxxxxxxx>; Andy Lutomirski <luto@xxxxxxxxxx>; >> Mohammed Gamal <mmorsy@xxxxxxxxxx>; Cathy Avery <cavery@xxxxxxxxxx>; linux- >> kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx >> Subject: [PATCH 3/6] x86/hyper-v: reenlightenment notifications support >> >> Hyper-V supports Live Migration notification. This is supposed to be used in conjunction with >> TSC emulation: when we are migrated to a host with different TSC frequency for some short >> period host emulates our accesses to TSC and sends us an interrupt to notify about the event. >> When we're done updating everything we can disable TSC emulation and everything will start >> working fast again. >> >> We didn't need these notifications before as Hyper-V guests are not supposed to use TSC as a >> clocksource: in Linux we even mark it as unstable on boot. Guests normally use 'tsc page' >> clocksouce and host updates its values on migrations automatically. >> >> Things change when we want to run nested virtualization: even when we pass through PV >> clocksources (kvm-clock or tsc page) to our guests we need to know TSC frequency and when it >> changes. >> >> Hyper-V Top Level Functional Specification (as of v5.0b) wrongly specifies >> EAX:BIT(12) of CPUID:0x40000009 as the feature identification bit. The right one to check is >> EAX:BIT(13) of CPUID:0x40000003. I was assured that the fix in on the way. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > [snip] > >> diff --git a/arch/x86/include/asm/irq_vectors.h >> b/arch/x86/include/asm/irq_vectors.h >> index 67421f649cfa..e71c1120426b 100644 >> --- a/arch/x86/include/asm/irq_vectors.h >> +++ b/arch/x86/include/asm/irq_vectors.h >> @@ -103,7 +103,12 @@ >> #endif >> >> #define MANAGED_IRQ_SHUTDOWN_VECTOR 0xef >> -#define LOCAL_TIMER_VECTOR 0xee >> + >> +#if IS_ENABLED(CONFIG_HYPERV) >> +#define HYPERV_REENLIGHTENMENT_VECTOR 0xee >> +#endif >> + >> +#define LOCAL_TIMER_VECTOR 0xed >> >> #define NR_VECTORS 256 > > [snip] > > Since you are pre-allocating a new vector, would you want to update the irq_cpustat_t > data structure and your interrupt handler to count the occurrences of these interrupts, > and update arch_show_interrupts() to show the count? Then cat /proc/interrupts > will show the count. The reenlightenment interrupts will presumably be rare, but so > are some of the others that are already counted and displayed, and it seems like > consistency should be maintained. I could do that. The problem with adding this entry to /proc/interrupts, as I see it, is that everyone who has CONFIG_HYPERV enabled in their distro will see one additional line which 99,9% of the time will be just '0'. I, however, see some value in seeing that L1 migration occured. I'll add a separate patch to the series and let x86 maintainers decide if it's worthy. Thanks, -- Vitaly _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
