Re: [PATCH] bitops: add _local bitops
From: Michael S. Tsirkin
Date: Wed May 09 2012 - 11:43:46 EST
On Wed, May 09, 2012 at 07:03:37AM -0700, H. Peter Anvin wrote:
> On 05/09/2012 06:45 AM, Michael S. Tsirkin wrote:
> > kvm needs to update some hypervisor variables atomically
> > in a sense that the operation can't be interrupted
> > in the middle. However the hypervisor always runs
> > on the same CPU so it does not need any memory
> > barrier or lock prefix.
> > At Peter Anvin's suggestion, add _local bitops for this purpose:
> > define them as non-atomics for x86 and (for now) atomics
> > for everyone else.
> > Uses are not restricted to virtualization: they
> > might be useful to communicate with an interrupt
> > handler if we know that it's running on the same CPU.
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> I don't think you can use the x86 nonatomics as-is, because they don't
> contain optimization barriers.
Just adding a memory clobber to asm will be enough, right?
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