From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Wei Liu <wei.liu2@citrix.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Xen-devel <xen-devel@lists.xen.org>,
Jan Beulich <JBeulich@suse.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Brian Woods <brian.woods@amd.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [PATCH 0/4] x86: Drop PVRDTSCP and fix MSR_TSC_AUX handling for guests
Date: Fri, 16 Nov 2018 14:55:27 -0500 [thread overview]
Message-ID: <20181116195527.GM30052@char.us.oracle.com> (raw)
In-Reply-To: <78463755-55b3-7914-227e-9351702b6764@citrix.com>
On Fri, Nov 16, 2018 at 05:43:42PM +0000, Andrew Cooper wrote:
> On 16/11/2018 10:11, Jan Beulich wrote:
> >>>> On 15.11.18 at 22:47, <andrew.cooper3@citrix.com> wrote:
> >> Boris has confirmed that noone appears to be using PVRDTSCP any more, and in
> >> the decade since it was introduced, guest kernel / hardware support has
> >> provided a better alternative.
> > Doesn't removal of functionality require knowing that it was never used
> > at all, rather than just knowing that nothing uses it anymore? What if
> > some old guest somewhere relies on it?
We have verified that it was never used.
>
> Its an all-or-nothing feature. The entirety of your VM userspace need
> to support it, or timing will go wrong on migrate.
>
> We already established that it appears to be a vestigial Oracle-ism for
> which no consumer side code ever appeared, and that isn't used.
>
> What is unacceptable is PVRDTSCP's implementation causing breakages in
> architectural behaviour for non-PVRDTSCP configurations, and one way or
> another, this needs fixing.
>
> Please can we make a decision, because I don't have to time (or indeed,
> the want) to and fix this a 3rd different way if that's going to run
> into a similar reaction.
>
> ~Andrew
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next prev parent reply other threads:[~2018-11-16 19:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-15 21:47 [PATCH 0/4] x86: Drop PVRDTSCP and fix MSR_TSC_AUX handling for guests Andrew Cooper
2018-11-15 21:47 ` [PATCH 1/4] x86: Begin to remove TSC mode PVRDTSCP Andrew Cooper
2018-11-19 15:25 ` Jan Beulich
2018-11-20 11:14 ` Andrew Cooper
2018-11-15 21:47 ` [PATCH 2/4] x86/pv: Remove deferred RDTSC{, P} handling in pv_emulate_privileged_op() Andrew Cooper
2018-11-20 8:40 ` Jan Beulich
2018-11-15 21:47 ` [PATCH 3/4] x86/msr: Handle MSR_TSC_AUX consistently for PV and HVM guests Andrew Cooper
2018-11-20 10:58 ` Jan Beulich
2018-11-26 15:28 ` Woods, Brian
2018-11-15 21:47 ` [PATCH 4/4] x86/pv: Expose RDTSCP to PV guests Andrew Cooper
2018-11-20 11:06 ` Jan Beulich
2018-11-20 11:29 ` Andrew Cooper
2018-11-20 15:14 ` Jan Beulich
2018-11-16 10:11 ` [PATCH 0/4] x86: Drop PVRDTSCP and fix MSR_TSC_AUX handling for guests Jan Beulich
2018-11-16 17:43 ` Andrew Cooper
2018-11-16 19:55 ` Konrad Rzeszutek Wilk [this message]
2018-11-19 8:29 ` Jan Beulich
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