Re: [Xen-devel] [PATCH] svm: Do not intercept RDTCS(P) when TSC scaling is supported by hardware

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Wednesday, April 25, 2012 3:27 AM
> To: Boris Ostrovsky; Dan Magenheimer
> Cc: wei.huang2@xxxxxxx; xen-devel; keir@xxxxxxx
> Subject: Re: [PATCH] svm: Do not intercept RDTCS(P) when TSC scaling is 
> supported by hardware
> 
> >>> On 20.04.12 at 04:21, Boris Ostrovsky <boris.ostrovsky@xxxxxxx> wrote:
> > # HG changeset patch
> > # User Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
> > # Date 1334875170 14400
> > # Node ID 55bf11ebce87ceb73fb2c372dcef170ec0bb4a18
> > # Parent  7c777cb8f705411b77c551f34ba88bdc09e38ab8
> > svm: Do not intercept RDTCS(P) when TSC scaling is supported by hardware
> >
> > When running in TSC_MODE_ALWAYS_EMULATE mode on processors that support
> > TSC scaling we don't need to intercept RDTSC/RDTSCP instructions.
> >
> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
> > Acked-by: Wei Huang <wei.huang2@xxxxxxx>
> > Tested-by: Wei Huang <wei.huang2@xxxxxxx>
> 
> So what's the status of the discussion around this patch? Were
> your concerns all addressed, Dan? Is there any re-submisson
> necessary/planned?

My concerns will be addressed when there is a fully-functional
adequately-tested full-stack implementation, rather than "we
have a new instruction that should solve (part of) this problem,
let's turn it on by default."

While I wish I could invest the time required to do (or
participate in) the testing, sadly I can't, so I understand
if my opinion is discarded.

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