Re: XSA-60 - how to get back to a sane state

[George Dunlap <george.dunlap@eu.citrix.com>]

On 12/02/2013 02:28 PM, Jan Beulich wrote:
> All,
>
> Jinsong's patches having been in for nearly a month now, but not
> being in a shape that would make releasing in 4.4 or backporting to
> the older trees desirable, we need to come to a conclusion on
> which way to go. Currently it looks like we have three options, but
> of course I'll be happy to see other (better!) ones proposed.
>
> 1) Stay with what we have.
>
> 2) Revert 86d60e85 ("VMX: flush cache when vmentry back to UC
> guest") in its entirety plus, perhaps, the change 62652c00 ("VMX:
> fix cr0.cd handling") did to vmx_ctxt_switch_to().
>
> 3) Apply the attached patch that Andrew and I have been putting
> together, with the caveat that it's still incomplete (see below).
>
> The latter two are based on the observation that the amount of
> cache flushing we do with what is in the master tree right now is
> more than what we did prior to that patch series but still
> insufficient. Hence the revert would get us back to the earlier
> state (and obviously eliminate the performance problems that
> were observed when doing too eager flushing), whereas
> applying the extra 5th patch would get us closer to a proper
> solution.

What's missing is a description of the pros and cons of 1 and 2.  Do you 
have any links to threads describing the problem?

  -George