All of lore.kernel.org
 help / color / mirror / Atom feed
From: Wei Liu <wei.liu2@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
	"Wei Liu" <wei.liu2@citrix.com>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	Xen-devel <xen-devel@lists.xen.org>,
	"Jan Beulich" <JBeulich@suse.com>,
	"Suravee Suthikulpanit" <suravee.suthikulpanit@amd.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 2/5] x86/pv: Avoid leaking other guests' MSR_TSC_AUX values into PV context
Date: Tue, 20 Feb 2018 15:22:44 +0000	[thread overview]
Message-ID: <20180220152244.2pv64jva6jsmodph@citrix.com> (raw)
In-Reply-To: <1519127923-23539-3-git-send-email-andrew.cooper3@citrix.com>

On Tue, Feb 20, 2018 at 11:58:40AM +0000, Andrew Cooper wrote:
> If the CPU pipeline supports RDTSCP or RDPID, a guest can observe the value in
> MSR_TSC_AUX, irrespective of whether the relevant CPUID features are
> advertised/hidden.
> 

This setup works only because CR4.TSD=0?

> At the moment, paravirt_ctxt_switch_to() only writes to MSR_TSC_AUX if
> TSC_MODE_PVRDTSCP mode is enabled, but this is not the default mode.
> Therefore, default PV guests can read the value from a previously scheduled
> HVM vcpu, or TSC_MODE_PVRDTSCP-enabled PV guest.
> 
> Alter the PV path to always write to MSR_TSC_AUX, using 0 in the common case.
> 
> To amortise overhead cost, introduce wrmsr_tsc_aux() which performs a lazy
> update of the MSR, and use this function consistently across the codebase.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

The code looks correct to me.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  reply	other threads:[~2018-02-20 15:22 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-20 11:58 [RFC PATCH 0/5] x86: Multiple fixes to MSR_TSC_AUX and RDTSCP handling for guests Andrew Cooper
2018-02-20 11:58 ` [PATCH 1/5] x86/hvm: Don't shadow the domain parameter in hvm_save_cpu_msrs() Andrew Cooper
2018-02-20 14:54   ` Roger Pau Monné
2018-02-20 15:12   ` Wei Liu
2018-02-23 13:53   ` Jan Beulich
2018-02-20 11:58 ` [PATCH 2/5] x86/pv: Avoid leaking other guests' MSR_TSC_AUX values into PV context Andrew Cooper
2018-02-20 15:22   ` Wei Liu [this message]
2018-02-20 15:26     ` Andrew Cooper
2018-02-20 15:32       ` Wei Liu
2018-02-20 15:49   ` Roger Pau Monné
2018-02-23 14:04   ` Jan Beulich
2018-02-23 14:22     ` Andrew Cooper
2018-02-23 15:09       ` Jan Beulich
2018-02-26 11:25   ` Jan Beulich
2018-02-26 19:11     ` [ping] " Andrew Cooper
2018-02-27  5:38       ` Tian, Kevin
2018-02-26 19:52   ` Boris Ostrovsky
2018-02-20 11:58 ` [PATCH 3/5] x86/time: Rework pv_soft_rdtsc() to aid further cleanup Andrew Cooper
2018-02-20 15:32   ` Wei Liu
2018-02-20 16:04   ` Roger Pau Monné
2018-02-20 16:07     ` Andrew Cooper
2018-02-23 14:38   ` Jan Beulich
2018-02-20 11:58 ` [PATCH 4/5] x86/pv: Remove deferred RDTSC{, P} handling in pv_emulate_privileged_op() Andrew Cooper
2018-02-20 16:08   ` Wei Liu
2018-02-20 16:28   ` Roger Pau Monné
2018-02-20 16:37     ` Andrew Cooper
2018-02-20 17:40       ` Roger Pau Monné
2018-02-23 14:40   ` Jan Beulich
2018-02-20 11:58 ` [PATCH 5/5] x86: Rework MSR_TSC_AUX handling from scratch Andrew Cooper
2018-02-20 17:03   ` Wei Liu
2018-02-20 17:42     ` Andrew Cooper
2018-02-21 11:08       ` Wei Liu
2018-02-20 17:35   ` Roger Pau Monné
2018-02-20 18:28     ` Andrew Cooper
2018-02-21 10:13       ` Roger Pau Monné
2018-02-21 11:36   ` [PATCH v2 " Andrew Cooper
2018-02-21 12:06     ` Wei Liu
2018-02-21 13:04     ` Roger Pau Monné
2018-02-23 15:05     ` Jan Beulich
2018-02-23 15:51       ` Andrew Cooper
2018-02-26 11:30         ` Jan Beulich
2018-02-26 19:12 ` [RFC PATCH 0/5] x86: Multiple fixes to MSR_TSC_AUX and RDTSCP handling for guests Andrew Cooper
2018-02-26 19:44   ` Boris Ostrovsky
2018-02-26 23:30     ` Andrew Cooper
2018-03-09 18:05       ` Boris Ostrovsky
2018-03-09 18:41         ` Andrew Cooper
2018-03-09 19:10           ` Boris Ostrovsky

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180220152244.2pv64jva6jsmodph@citrix.com \
    --to=wei.liu2@citrix.com \
    --cc=JBeulich@suse.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=boris.ostrovsky@oracle.com \
    --cc=jun.nakajima@intel.com \
    --cc=kevin.tian@intel.com \
    --cc=roger.pau@citrix.com \
    --cc=suravee.suthikulpanit@amd.com \
    --cc=xen-devel@lists.xen.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.