* [MODERATED] [PATCH] taa fix
@ 2019-11-07 2:26 Josh Poimboeuf
2019-11-07 2:41 ` [MODERATED] " Tyler Hicks
2019-11-07 9:25 ` Borislav Petkov
0 siblings, 2 replies; 7+ messages in thread
From: Josh Poimboeuf @ 2019-11-07 2:26 UTC (permalink / raw)
To: speck
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From: Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
For new IBRS_ALL CPUs, the Enhanced IBRS check at the beginning of
cpu_bugs_smt_update() causes the function to return early,
unintentionally skipping the MDS and TAA logic.
I don't think it's a problem for MDS, because AFAICT there appears to be
no overlap between IBRS_ALL and MDS-affected CPUs. So the MDS
mitigation would be disabled and nothing would need to be done in this
function anyway.
But for TAA, the TAA_MSG_SMT string will never get printed on Cascade
Lake and newer.
The check is superfluous anyway: when 'spectre_v2_enabled' is
SPECTRE_V2_IBRS_ENHANCED, 'spectre_v2_user' is always
SPECTRE_V2_USER_NONE, and so the 'spectre_v2_user' switch statement
handles it appropriately by doing nothing. So just remove the check.
Fixes: 1b42f017415b ("x86/speculation/taa: Add mitigation for TSX Async Abort")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/cpu/bugs.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 850005590167..4c7b0fa15a19 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -886,10 +886,6 @@ static void update_mds_branch_idle(void)
void cpu_bugs_smt_update(void)
{
- /* Enhanced IBRS implies STIBP. No update required. */
- if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
- return;
-
mutex_lock(&spec_ctrl_mutex);
switch (spectre_v2_user) {
--
2.20.1
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^ permalink raw reply related [flat|nested] 7+ messages in thread* [MODERATED] Re: [PATCH] taa fix
2019-11-07 2:26 [MODERATED] [PATCH] taa fix Josh Poimboeuf
@ 2019-11-07 2:41 ` Tyler Hicks
2019-11-07 9:25 ` Borislav Petkov
1 sibling, 0 replies; 7+ messages in thread
From: Tyler Hicks @ 2019-11-07 2:41 UTC (permalink / raw)
To: speck
On 2019-11-06 20:26:46, speck for Josh Poimboeuf wrote:
> From: Josh Poimboeuf <jpoimboe@redhat.com>
> Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
>
> For new IBRS_ALL CPUs, the Enhanced IBRS check at the beginning of
> cpu_bugs_smt_update() causes the function to return early,
> unintentionally skipping the MDS and TAA logic.
>
> I don't think it's a problem for MDS, because AFAICT there appears to be
> no overlap between IBRS_ALL and MDS-affected CPUs. So the MDS
> mitigation would be disabled and nothing would need to be done in this
> function anyway.
>
> But for TAA, the TAA_MSG_SMT string will never get printed on Cascade
> Lake and newer.
>
> The check is superfluous anyway: when 'spectre_v2_enabled' is
> SPECTRE_V2_IBRS_ENHANCED, 'spectre_v2_user' is always
> SPECTRE_V2_USER_NONE, and so the 'spectre_v2_user' switch statement
> handles it appropriately by doing nothing. So just remove the check.
>
> Fixes: 1b42f017415b ("x86/speculation/taa: Add mitigation for TSX Async Abort")
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
I went back through my testing logs and verified that I didn't see the
TAA_MSG_SMT message printed on the Cascade Lake machine I tested with.
Thanks for noticing and fixing it.
Tyler
> ---
> arch/x86/kernel/cpu/bugs.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 850005590167..4c7b0fa15a19 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -886,10 +886,6 @@ static void update_mds_branch_idle(void)
>
> void cpu_bugs_smt_update(void)
> {
> - /* Enhanced IBRS implies STIBP. No update required. */
> - if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
> - return;
> -
> mutex_lock(&spec_ctrl_mutex);
>
> switch (spectre_v2_user) {
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 7+ messages in thread* [MODERATED] Re: [PATCH] taa fix
2019-11-07 2:26 [MODERATED] [PATCH] taa fix Josh Poimboeuf
2019-11-07 2:41 ` [MODERATED] " Tyler Hicks
@ 2019-11-07 9:25 ` Borislav Petkov
2019-11-07 13:47 ` Josh Poimboeuf
1 sibling, 1 reply; 7+ messages in thread
From: Borislav Petkov @ 2019-11-07 9:25 UTC (permalink / raw)
To: speck
On Wed, Nov 06, 2019 at 08:26:46PM -0600, speck for Josh Poimboeuf wrote:
> From: Josh Poimboeuf <jpoimboe@redhat.com>
> Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
Subject should be something like "Print TAA_MSG_SMT on IBRS_ALL CPUs
too" or so.
> For new IBRS_ALL CPUs, the Enhanced IBRS check at the beginning of
> cpu_bugs_smt_update() causes the function to return early,
> unintentionally skipping the MDS and TAA logic.
>
> I don't think it's a problem for MDS, because AFAICT there appears to be
> no overlap between IBRS_ALL and MDS-affected CPUs. So the MDS
> mitigation would be disabled and nothing would need to be done in this
> function anyway.
>
> But for TAA, the TAA_MSG_SMT string will never get printed on Cascade
> Lake and newer.
>
> The check is superfluous anyway: when 'spectre_v2_enabled' is
> SPECTRE_V2_IBRS_ENHANCED, 'spectre_v2_user' is always
> SPECTRE_V2_USER_NONE, and so the 'spectre_v2_user' switch statement
> handles it appropriately by doing nothing. So just remove the check.
>
> Fixes: 1b42f017415b ("x86/speculation/taa: Add mitigation for TSX Async Abort")
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> arch/x86/kernel/cpu/bugs.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 850005590167..4c7b0fa15a19 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -886,10 +886,6 @@ static void update_mds_branch_idle(void)
>
> void cpu_bugs_smt_update(void)
> {
> - /* Enhanced IBRS implies STIBP. No update required. */
> - if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
> - return;
> -
> mutex_lock(&spec_ctrl_mutex);
>
> switch (spectre_v2_user) {
> --
With that addressed:
Reviewed-by: Borislav Petkov <bp@suse.de>
--
Regards/Gruss,
Boris.
SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg
--
^ permalink raw reply [flat|nested] 7+ messages in thread* [MODERATED] Re: [PATCH] taa fix
2019-11-07 9:25 ` Borislav Petkov
@ 2019-11-07 13:47 ` Josh Poimboeuf
2019-11-07 13:49 ` Borislav Petkov
0 siblings, 1 reply; 7+ messages in thread
From: Josh Poimboeuf @ 2019-11-07 13:47 UTC (permalink / raw)
To: speck
On Thu, Nov 07, 2019 at 10:25:33AM +0100, speck for Borislav Petkov wrote:
> On Wed, Nov 06, 2019 at 08:26:46PM -0600, speck for Josh Poimboeuf wrote:
> > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
>
> Subject should be something like "Print TAA_MSG_SMT on IBRS_ALL CPUs
> too" or so.
The subject is indeed overly broad. Though I wanted to highlight that
it's a fix. How about
x86/speculation/taa: Fix TAA_MSG_SMT printk on IBRS_ALL CPUs
?
--
Josh
^ permalink raw reply [flat|nested] 7+ messages in thread
* [MODERATED] Re: [PATCH] taa fix
2019-11-07 13:47 ` Josh Poimboeuf
@ 2019-11-07 13:49 ` Borislav Petkov
2019-11-07 14:59 ` Josh Poimboeuf
0 siblings, 1 reply; 7+ messages in thread
From: Borislav Petkov @ 2019-11-07 13:49 UTC (permalink / raw)
To: speck
On Thu, Nov 07, 2019 at 07:47:14AM -0600, speck for Josh Poimboeuf wrote:
> On Thu, Nov 07, 2019 at 10:25:33AM +0100, speck for Borislav Petkov wrote:
> > On Wed, Nov 06, 2019 at 08:26:46PM -0600, speck for Josh Poimboeuf wrote:
> > > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > > Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
> >
> > Subject should be something like "Print TAA_MSG_SMT on IBRS_ALL CPUs
> > too" or so.
>
> The subject is indeed overly broad. Though I wanted to highlight that
> it's a fix. How about
>
> x86/speculation/taa: Fix TAA_MSG_SMT printk on IBRS_ALL CPUs
>
> ?
Make that "Fix printing" and you're good.
Because it is not really fixing the printk but it is making it print
again. But we're bikeshedding...
:-)
--
Regards/Gruss,
Boris.
SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg
--
^ permalink raw reply [flat|nested] 7+ messages in thread* [MODERATED] Re: [PATCH] taa fix
2019-11-07 13:49 ` Borislav Petkov
@ 2019-11-07 14:59 ` Josh Poimboeuf
2019-11-07 15:04 ` Thomas Gleixner
0 siblings, 1 reply; 7+ messages in thread
From: Josh Poimboeuf @ 2019-11-07 14:59 UTC (permalink / raw)
To: speck
On Thu, Nov 07, 2019 at 02:49:52PM +0100, speck for Borislav Petkov wrote:
> On Thu, Nov 07, 2019 at 07:47:14AM -0600, speck for Josh Poimboeuf wrote:
> > On Thu, Nov 07, 2019 at 10:25:33AM +0100, speck for Borislav Petkov wrote:
> > > On Wed, Nov 06, 2019 at 08:26:46PM -0600, speck for Josh Poimboeuf wrote:
> > > > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > > > Subject: [PATCH] x86/speculation/taa: Fix TAA_MSG_SMT printk
> > >
> > > Subject should be something like "Print TAA_MSG_SMT on IBRS_ALL CPUs
> > > too" or so.
> >
> > The subject is indeed overly broad. Though I wanted to highlight that
> > it's a fix. How about
> >
> > x86/speculation/taa: Fix TAA_MSG_SMT printk on IBRS_ALL CPUs
> >
> > ?
>
> Make that "Fix printing" and you're good.
Fair enough. I'll go with
x86/speculation/taa: Fix printing of TAA_MSG_SMT on IBRS_ALL CPUs
--
Josh
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] taa fix
2019-11-07 14:59 ` Josh Poimboeuf
@ 2019-11-07 15:04 ` Thomas Gleixner
0 siblings, 0 replies; 7+ messages in thread
From: Thomas Gleixner @ 2019-11-07 15:04 UTC (permalink / raw)
To: speck
On Thu, 7 Nov 2019, speck for Josh Poimboeuf wrote:
> On Thu, Nov 07, 2019 at 02:49:52PM +0100, speck for Borislav Petkov wrote:
> > Make that "Fix printing" and you're good.
>
> Fair enough. I'll go with
>
> x86/speculation/taa: Fix printing of TAA_MSG_SMT on IBRS_ALL CPUs
No need to resend. I already fixed it locally.
Thanks,
tglx
^ permalink raw reply [flat|nested] 7+ messages in thread
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2019-11-07 2:26 [MODERATED] [PATCH] taa fix Josh Poimboeuf
2019-11-07 2:41 ` [MODERATED] " Tyler Hicks
2019-11-07 9:25 ` Borislav Petkov
2019-11-07 13:47 ` Josh Poimboeuf
2019-11-07 13:49 ` Borislav Petkov
2019-11-07 14:59 ` Josh Poimboeuf
2019-11-07 15:04 ` Thomas Gleixner
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