Messages in this thread | | | Date | Wed, 26 Jan 2011 13:06:45 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH 01/16] KVM-HDR: register KVM basic header infrastructure |
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On 01/24/2011 08:06 PM, Glauber Costa wrote: > KVM, which stands for KVM Virtual Memory (I wanted to call it KVM Virtual Mojito), > is a piece of shared memory that is visible to both the hypervisor and the guest > kernel - but not the guest userspace. > > The basic idea is that the guest can tell the hypervisor about a specific > piece of memory, and what it expects to find in there. This is a generic > abstraction, that goes to userspace (qemu) if KVM (the hypervisor) can't > handle a specific request, thus giving us flexibility in some features > in the future. > > KVM (The hypervisor) can change the contents of this piece of memory at > will. This works well with paravirtual information, and hopefully > normal guest memory - like last update time for the watchdog, for > instance. > > This is basic KVM registration headers. I am keeping headers > separate to facilitate backports to people who wants to backport > the kernel part but not the hypervisor, or the other way around. > > Signed-off-by: Glauber Costa<glommer@redhat.com> > CC: Avi Kivity<avi@redhat.com> > --- > arch/x86/include/asm/kvm_para.h | 11 +++++++++++ > 1 files changed, 11 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index a427bf7..b0b0ee0 100644 > --- a/arch/x86/include/asm/kvm_para.h > +++ b/arch/x86/include/asm/kvm_para.h > @@ -21,6 +21,7 @@ > */ > #define KVM_FEATURE_CLOCKSOURCE2 3 > #define KVM_FEATURE_ASYNC_PF 4 > +#define KVM_FEATURE_MEMORY_AREA 5 > > /* The last 8 bits are used to indicate how to interpret the flags field > * in pvclock structure. If no bits are set, all flags are ignored. > @@ -35,6 +36,16 @@ > #define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01 > #define MSR_KVM_ASYNC_PF_EN 0x4b564d02 > > +#define MSR_KVM_REGISTER_MEM_AREA 0x4b564d03 > + > +struct kvm_memory_area { > + __u64 base; > + __u32 size; > + __u32 type; > + __u8 result; > + __u8 pad[3]; > +}; > + > #define KVM_MAX_MMU_OP_BATCH 32
I'm guessing the protocol here is:
- guest fills in ->base/size/type - issues wrmsr - host registers the memory and updates ->result - guest examines ->result
there are two issues with this approach:
- it doesn't lend itself will to live migration. Extra state must be maintained in the hypervisor. - it isn't how normal hardware operates
what's wrong with extending the normal approach of one msr per feature?
-- error compiling committee.c: too many arguments to function
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