Re: [PATCH 14/18] Fix a possible backwards warp of kvmclock

From: Rik van Riel
Date: Wed Jul 14 2010 - 22:37:10 EST


On 07/12/2010 10:25 PM, Zachary Amsden wrote:
Kernel time, which advances in discrete steps may progress much slower
than TSC. As a result, when kvmclock is adjusted to a new base, the
apparent time to the guest, which runs at a much higher, nsec scaled
rate based on the current TSC, may have already been observed to have
a larger value (kernel_ns + scaled tsc) than the value to which we are
setting it (kernel_ns + 0).

We must instead compute the clock as potentially observed by the guest
for kernel_ns to make sure it does not go backwards.

Signed-off-by: Zachary Amsden<zamsden@xxxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

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