* [PATCH] x86,perf: Disable intel_bts when PTI
@ 2018-01-14 10:27 Peter Zijlstra
2018-01-14 10:46 ` [tip:x86/pti] " tip-bot for Peter Zijlstra
2018-01-14 10:50 ` [PATCH] " Greg KH
0 siblings, 2 replies; 6+ messages in thread
From: Peter Zijlstra @ 2018-01-14 10:27 UTC (permalink / raw)
To: Thomas Gleixner
Cc: linux-kernel, Vince Weaver, torvalds, robert, luto, mingo, hughd,
greg, Alexander Shishkin
The intel_bts driver does not use the 'normal' BTS buffer we allocated
space for in the cpu_entry_area but instead uses the memory allocated
for the perf AUX buffer.
This obviously comes apart when using PTI because then the kernel
mapping; which includes that AUX buffer memory; disappears.
For now disable this driver when PTI is enabled, we'll try and sort
something out later.
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Reported-by: Robert Święcki <robert@swiecki.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/events/intel/bts.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 141e07b06216..24ffa1e88cf9 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -582,6 +582,24 @@ static __init int bts_init(void)
if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts)
return -ENODEV;
+ if (boot_cpu_has(X86_FEATURE_PTI)) {
+ /*
+ * BTS hardware writes through a virtual memory map we must
+ * either use the kernel physical map, or the user mapping of
+ * the AUX buffer.
+ *
+ * However, since this driver supports per-CPU and per-task inherit
+ * we cannot use the user mapping since it will not be availble
+ * if we're not running the owning process.
+ *
+ * With PTI we can't use the kernal map either, because its not
+ * there when we run userspace.
+ *
+ * For now, disable this driver when using PTI.
+ */
+ return -ENODEV;
+ }
+
bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE |
PERF_PMU_CAP_EXCLUSIVE;
bts_pmu.task_ctx_nr = perf_sw_context;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip:x86/pti] x86,perf: Disable intel_bts when PTI
2018-01-14 10:27 [PATCH] x86,perf: Disable intel_bts when PTI Peter Zijlstra
@ 2018-01-14 10:46 ` tip-bot for Peter Zijlstra
2018-01-14 10:50 ` [PATCH] " Greg KH
1 sibling, 0 replies; 6+ messages in thread
From: tip-bot for Peter Zijlstra @ 2018-01-14 10:46 UTC (permalink / raw)
To: linux-tip-commits
Cc: hpa, linux-kernel, tglx, mingo, peterz, vince, vincent.weaver,
alexander.shishkin, robert
Commit-ID: 99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8
Gitweb: https://git.kernel.org/tip/99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Sun, 14 Jan 2018 11:27:13 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Jan 2018 11:42:10 +0100
x86,perf: Disable intel_bts when PTI
The intel_bts driver does not use the 'normal' BTS buffer which is exposed
through the cpu_entry_area but instead uses the memory allocated for the
perf AUX buffer.
This obviously comes apart when using PTI because then the kernel mapping;
which includes that AUX buffer memory; disappears. Fixing this requires to
expose a mapping which is visible in all context and that's not trivial.
As a quick fix disable this driver when PTI is enabled to prevent
malfunction.
Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig")
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Reported-by: Robert Święcki <robert@swiecki.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: greg@kroah.com
Cc: hughd@google.com
Cc: luto@amacapital.net
Cc: Vince Weaver <vince@deater.net>
Cc: torvalds@linux-foundation.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180114102713.GB6166@worktop.programming.kicks-ass.net
---
arch/x86/events/intel/bts.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 141e07b..24ffa1e 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -582,6 +582,24 @@ static __init int bts_init(void)
if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts)
return -ENODEV;
+ if (boot_cpu_has(X86_FEATURE_PTI)) {
+ /*
+ * BTS hardware writes through a virtual memory map we must
+ * either use the kernel physical map, or the user mapping of
+ * the AUX buffer.
+ *
+ * However, since this driver supports per-CPU and per-task inherit
+ * we cannot use the user mapping since it will not be availble
+ * if we're not running the owning process.
+ *
+ * With PTI we can't use the kernal map either, because its not
+ * there when we run userspace.
+ *
+ * For now, disable this driver when using PTI.
+ */
+ return -ENODEV;
+ }
+
bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE |
PERF_PMU_CAP_EXCLUSIVE;
bts_pmu.task_ctx_nr = perf_sw_context;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] x86,perf: Disable intel_bts when PTI
2018-01-14 10:27 [PATCH] x86,perf: Disable intel_bts when PTI Peter Zijlstra
2018-01-14 10:46 ` [tip:x86/pti] " tip-bot for Peter Zijlstra
@ 2018-01-14 10:50 ` Greg KH
2018-01-14 10:52 ` Thomas Gleixner
2018-01-14 12:54 ` Ingo Molnar
1 sibling, 2 replies; 6+ messages in thread
From: Greg KH @ 2018-01-14 10:50 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Thomas Gleixner, linux-kernel, Vince Weaver, torvalds, robert,
luto, mingo, hughd, Alexander Shishkin
On Sun, Jan 14, 2018 at 11:27:13AM +0100, Peter Zijlstra wrote:
>
> The intel_bts driver does not use the 'normal' BTS buffer we allocated
> space for in the cpu_entry_area but instead uses the memory allocated
> for the perf AUX buffer.
>
> This obviously comes apart when using PTI because then the kernel
> mapping; which includes that AUX buffer memory; disappears.
>
> For now disable this driver when PTI is enabled, we'll try and sort
> something out later.
>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> Reported-by: Robert Święcki <robert@swiecki.net>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Can you add a:
Cc: stable <stable@vger.kernel.org>
please?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86,perf: Disable intel_bts when PTI
2018-01-14 10:50 ` [PATCH] " Greg KH
@ 2018-01-14 10:52 ` Thomas Gleixner
2018-01-14 12:54 ` Ingo Molnar
1 sibling, 0 replies; 6+ messages in thread
From: Thomas Gleixner @ 2018-01-14 10:52 UTC (permalink / raw)
To: Greg KH
Cc: Peter Zijlstra, linux-kernel, Vince Weaver, torvalds, robert,
luto, mingo, hughd, Alexander Shishkin
[-- Attachment #1: Type: text/plain, Size: 868 bytes --]
On Sun, 14 Jan 2018, Greg KH wrote:
> On Sun, Jan 14, 2018 at 11:27:13AM +0100, Peter Zijlstra wrote:
> >
> > The intel_bts driver does not use the 'normal' BTS buffer we allocated
> > space for in the cpu_entry_area but instead uses the memory allocated
> > for the perf AUX buffer.
> >
> > This obviously comes apart when using PTI because then the kernel
> > mapping; which includes that AUX buffer memory; disappears.
> >
> > For now disable this driver when PTI is enabled, we'll try and sort
> > something out later.
> >
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> > Reported-by: Robert Święcki <robert@swiecki.net>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> Can you add a:
> Cc: stable <stable@vger.kernel.org>
> please?
Already in the commit ...
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86,perf: Disable intel_bts when PTI
2018-01-14 10:50 ` [PATCH] " Greg KH
2018-01-14 10:52 ` Thomas Gleixner
@ 2018-01-14 12:54 ` Ingo Molnar
2018-01-14 13:27 ` Greg KH
1 sibling, 1 reply; 6+ messages in thread
From: Ingo Molnar @ 2018-01-14 12:54 UTC (permalink / raw)
To: Greg KH
Cc: Peter Zijlstra, Thomas Gleixner, linux-kernel, Vince Weaver,
torvalds, robert, luto, hughd, Alexander Shishkin
* Greg KH <greg@kroah.com> wrote:
> On Sun, Jan 14, 2018 at 11:27:13AM +0100, Peter Zijlstra wrote:
> >
> > The intel_bts driver does not use the 'normal' BTS buffer we allocated
> > space for in the cpu_entry_area but instead uses the memory allocated
> > for the perf AUX buffer.
> >
> > This obviously comes apart when using PTI because then the kernel
> > mapping; which includes that AUX buffer memory; disappears.
> >
> > For now disable this driver when PTI is enabled, we'll try and sort
> > something out later.
> >
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> > Reported-by: Robert Święcki <robert@swiecki.net>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> Can you add a:
> Cc: stable <stable@vger.kernel.org>
> please?
Note that these fixes are all going into tip:x86/pti, which is still a backporting
friendly linear set of commits that should all be backported.
So once 99a9dc98ba52 goes upstream, all of v4.14..99a9dc98ba52 the remaining bits
can go to -stable as well.
Will keep you updated about the latest status periodically, right now the latest
that is already upstream is:
de791821c295: x86/pti: Rename BUG_CPU_INSECURE to BUG_CPU_MELTDOWN
i.e. all 194 commits in the v4.14..de791821c295 range should be queued up for
-stable. (And most of them already are.)
There are 28 new commits in tip:x86/pti that will (hopefully) go upstream later
today.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86,perf: Disable intel_bts when PTI
2018-01-14 12:54 ` Ingo Molnar
@ 2018-01-14 13:27 ` Greg KH
0 siblings, 0 replies; 6+ messages in thread
From: Greg KH @ 2018-01-14 13:27 UTC (permalink / raw)
To: Ingo Molnar
Cc: Peter Zijlstra, Thomas Gleixner, linux-kernel, Vince Weaver,
torvalds, robert, luto, hughd, Alexander Shishkin
On Sun, Jan 14, 2018 at 01:54:44PM +0100, Ingo Molnar wrote:
>
> * Greg KH <greg@kroah.com> wrote:
>
> > On Sun, Jan 14, 2018 at 11:27:13AM +0100, Peter Zijlstra wrote:
> > >
> > > The intel_bts driver does not use the 'normal' BTS buffer we allocated
> > > space for in the cpu_entry_area but instead uses the memory allocated
> > > for the perf AUX buffer.
> > >
> > > This obviously comes apart when using PTI because then the kernel
> > > mapping; which includes that AUX buffer memory; disappears.
> > >
> > > For now disable this driver when PTI is enabled, we'll try and sort
> > > something out later.
> > >
> > > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > > Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> > > Reported-by: Robert Święcki <robert@swiecki.net>
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> >
> > Can you add a:
> > Cc: stable <stable@vger.kernel.org>
> > please?
>
> Note that these fixes are all going into tip:x86/pti, which is still a backporting
> friendly linear set of commits that should all be backported.
>
> So once 99a9dc98ba52 goes upstream, all of v4.14..99a9dc98ba52 the remaining bits
> can go to -stable as well.
>
> Will keep you updated about the latest status periodically, right now the latest
> that is already upstream is:
>
> de791821c295: x86/pti: Rename BUG_CPU_INSECURE to BUG_CPU_MELTDOWN
>
> i.e. all 194 commits in the v4.14..de791821c295 range should be queued up for
> -stable. (And most of them already are.)
I hope I got all of those in that branch already, as I've been watching
it :)
> There are 28 new commits in tip:x86/pti that will (hopefully) go upstream later
> today.
Great, again, thanks for doing it this way, it has made it much easier
for me.
greg k-h
^ permalink raw reply [flat|nested] 6+ messages in thread
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2018-01-14 10:46 ` [tip:x86/pti] " tip-bot for Peter Zijlstra
2018-01-14 10:50 ` [PATCH] " Greg KH
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