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Date: Wed, 30 May 2012 13:54:25 +0200 From: Jan Kiszka <jan.kiszka@...mens.com> To: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> CC: Jeremy Fitzhardinge <jeremy@...p.org>, Greg Kroah-Hartman <gregkh@...e.de>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, "H. Peter Anvin" <hpa@...or.com>, Avi Kivity <avi@...hat.com>, X86 <x86@...nel.org>, Gleb Natapov <gleb@...hat.com>, Ingo Molnar <mingo@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Xen Devel <xen-devel@...ts.xensource.com>, KVM <kvm@...r.kernel.org>, linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>, Virtualization <virtualization@...ts.linux-foundation.org>, Andi Kleen <andi@...stfloor.org>, Stephan Diestelhorst <stephan.diestelhorst@....com>, Attilio Rao <attilio.rao@...rix.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Stefano Stabellini <stefano.stabellini@...citrix.com> Subject: Re: [PATCH RFC V8 17/17] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock On 2012-05-02 12:09, Raghavendra K T wrote: > From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> > > KVM_HC_KICK_CPU hypercall added to wakeup halted vcpu in paravirtual spinlock > enabled guest. > > KVM_FEATURE_PV_UNHALT enables guest to check whether pv spinlock can be enabled > in guest. > > Thanks Alex for KVM_HC_FEATURES inputs and Vatsa for rewriting KVM_HC_KICK_CPU This contains valuable documentation for features that are already supported. Can you break them out and post as separate patch already? One comment on them below. > > Signed-off-by: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> > Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> > --- > Documentation/virtual/kvm/cpuid.txt | 4 ++ > Documentation/virtual/kvm/hypercalls.txt | 60 ++++++++++++++++++++++++++++++ > 2 files changed, 64 insertions(+), 0 deletions(-) > diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt > index 8820685..062dff9 100644 > --- a/Documentation/virtual/kvm/cpuid.txt > +++ b/Documentation/virtual/kvm/cpuid.txt > @@ -39,6 +39,10 @@ KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs > KVM_FEATURE_ASYNC_PF || 4 || async pf can be enabled by > || || writing to msr 0x4b564d02 > ------------------------------------------------------------------------------ > +KVM_FEATURE_PV_UNHALT || 6 || guest checks this feature bit > + || || before enabling paravirtualized > + || || spinlock support. > +------------------------------------------------------------------------------ > KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side > || || per-cpu warps are expected in > || || kvmclock. > diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt > new file mode 100644 > index 0000000..bc3f14a > --- /dev/null > +++ b/Documentation/virtual/kvm/hypercalls.txt > @@ -0,0 +1,60 @@ > +KVM Hypercalls Documentation > +=========================== > +The template for each hypercall is: > +1. Hypercall name, value. > +2. Architecture(s) > +3. Status (deprecated, obsolete, active) > +4. Purpose > + > +1. KVM_HC_VAPIC_POLL_IRQ > +------------------------ > +Value: 1 > +Architecture: x86 > +Purpose: None Purpose: Trigger guest exit so that the host can check for pending interrupts on reentry. > + > +2. KVM_HC_MMU_OP > +------------------------ > +Value: 2 > +Architecture: x86 > +Status: deprecated. > +Purpose: Support MMU operations such as writing to PTE, > +flushing TLB, release PT. > + > +3. KVM_HC_FEATURES > +------------------------ > +Value: 3 > +Architecture: PPC > +Status: active > +Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid > +used to enumerate which hypercalls are available. On PPC, either device tree > +based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration > +mechanism (which is this hypercall) can be used. > + > +4. KVM_HC_PPC_MAP_MAGIC_PAGE > +------------------------ > +Value: 4 > +Architecture: PPC > +Status: active > +Purpose: To enable communication between the hypervisor and guest there is a > +shared page that contains parts of supervisor visible register state. > +The guest can map this shared page to access its supervisor register through > +memory using this hypercall. > + > +5. KVM_HC_KICK_CPU > +------------------------ > +Value: 5 > +Architecture: x86 > +Status: active > +Purpose: Hypercall used to wakeup a vcpu from HLT state > + > +Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest > +kernel mode for an event to occur (ex: a spinlock to become available) can > +execute HLT instruction once it has busy-waited for more than a threshold > +time-interval. Execution of HLT instruction would cause the hypervisor to put > +the vcpu to sleep until occurence of an appropriate event. Another vcpu of the > +same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall, > +specifying APIC ID of the vcpu to be wokenup. > + > +TODO: > +1. more information on input and output needed? > +2. Add more detail to purpose of hypercalls. Thanks, Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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