On 06/18/2012 05:56 PM, Michael S. Tsirkin wrote: > On Mon, Jun 18, 2012 at 05:20:01PM +0300, Avi Kivity wrote: >> On 06/14/2012 04:53 PM, Michael S. Tsirkin wrote: >> > Document the new EOI MSR. Couldn't decide whether this change belongs >> > conceptually on guest or host side, so a separate patch. >> > >> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> >> > --- >> > Documentation/virtual/kvm/msr.txt | 32 ++++++++++++++++++++++++++++++++ >> > 1 file changed, 32 insertions(+) >> > >> > diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt >> > index 96b41bd..6ae5a85 100644 >> > --- a/Documentation/virtual/kvm/msr.txt >> > +++ b/Documentation/virtual/kvm/msr.txt >> > @@ -223,3 +223,35 @@ MSR_KVM_STEAL_TIME: 0x4b564d03 >> > steal: the amount of time in which this vCPU did not run, in >> > nanoseconds. Time during which the vcpu is idle, will not be >> > reported as steal time. >> > + >> > +MSR_KVM_EOI_EN: 0x4b564d04 >> > + data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0 >> > + when disabled. When enabled, bits 63-1 hold 2-byte aligned physical address >> > + of a 2 byte memory area which must be in guest RAM and must be zeroed. >> >> 2 byte aligned means we must never access it on the host with a >2 byte >> instruction, or we risk touching unmapped memory. > > Yes. So ... that's correct for any length. > The patch actually accesses a single byte only. > > Could you clarify what you are saying here please? > It means, if we want to use __set_bit() (and if __set_bit wants to access this as a long) then we can get an exception. The spec shouldn't limit us in this way, even if the implementation is okay. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
