Re: [Xen-devel] [PATCH] x86 linux: prevent halted VCPUs from eating up CPU bandwidth

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29 May 2006, at 15:35, Jan Beulich wrote:

> Since there was no reply to an earlier inquiry regarding this, here's 
> a patch.
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
safe_halt() should simply be HYPERVISOR_block() -- the hypercall 
implicitly reenables interrupt delivery for the calling VCPU, so no 
need to call __sti() explicitly.
halt() is a bit trickier -- given that it is executed (as far as I can 
tell) only in contexts where the CPU has reached "end of life" (it's 
crashed, or offlined, or shut down for some other reason) it might make 
sense to define halt() as VCPUOP_down. Or, just in case it is used in 
places with interrupts still enabled, where the CPU may have a future:
#define halt() (irqs_disabled() ? HYPERVISOR_vcpu_op(VCPUOP_down) : 
HYPERVISOR_block())
 -- Keir


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