Re: [PATCH v2 6/6] Describe KVM_MSR_STEAL_TIME

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On 01/28/2011 09:52 PM, Glauber Costa wrote:
This patch adds documentation about usage of the newly
introduced KVM_MSR_STEAL_TIME.


+
+MSR_KVM_STEAL_TIME: 0x4b564d03
+
+	data: 4-byte alignment physical address of a memory area which must be
+	in guest RAM, plus an enable bit in bit 0.

64-byte aligned:
- avoids wrapping around a page boundary, which may let us optimize things later on (see kvm_write_guest_cached()).
- gives us 5 more unused bits to enable more options

  This memory is expected to
+	hold a copy of the following structure:
+
+	struct kvm_steal_time {
+	  	__u64 steal;
+ 		__u32 version;
+ 		__u32 flags;
+	 	__u32 pad[6];
+	}
+
+	whose data will be filled in by the hypervisor periodically. Only one
+	write, or registration, is needed for each VCPU. The interval between
+	updates of this structure is arbitrary and implementation-dependent.
+	The hypervisor may update this structure at any time it sees fit until
+	anything with bit0 == 0 is written to it.
+
+	Fields have the following meanings:
+
+		version: guest has to check version before and after grabbing
+		time information and check that they are both equal and even.
+		An odd version indicates an in-progress update.
+
+		flags: At this point, always zero. May be used to indicate
+		changes in this structure in the future.
+
+		steal: the amount of time in which this vCPU did not run, in
+		nanoseconds.
+

The guest must initialize the entire 64-byte structure to zero before enabling the feature.

--
error compiling committee.c: too many arguments to function

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