Changes to the AMD Thresholding sysfs code prevents sysfs writes from
updating the underlying registers once CPU init is completed, i.e.
"threshold_banks" is set.
Allow the registers to be updated if the thresholding interface is
already initialized or if in the init path. Use the "set_lvt_off" value
to indicate if running in the init path, since this value is only set
during init.
Fixes: a037f3ca0ea0 ("x86/mce/amd: Make threshold bank setting hotplug robust")
Signed-off-by: Yazen Ghannam <[email protected]>
---
arch/x86/kernel/cpu/mce/amd.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 2eadc7c4c902..408c9546ea0b 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -400,8 +400,12 @@ static void threshold_restart_bank(void *_tr)
struct thresh_restart *tr = _tr;
u32 hi, lo;
- /* sysfs write might race against an offline operation */
- if (this_cpu_read(threshold_banks))
+ /*
+ * sysfs write might race against an offline operation.
+ * Prevent register writes if threshold_banks are not set and this is
+ * not called from the init path as indicated by "set_lvt_off".
+ */
+ if (!(this_cpu_read(threshold_banks) || tr->set_lvt_off))
return;
rdmsr(tr->b->address, lo, hi);
--
2.25.1
On Tue, Dec 07, 2021 at 07:30:28PM +0000, Yazen Ghannam wrote:
> Changes to the AMD Thresholding sysfs code prevents sysfs writes from
> updating the underlying registers once CPU init is completed, i.e.
> "threshold_banks" is set.
>
> Allow the registers to be updated if the thresholding interface is
> already initialized or if in the init path. Use the "set_lvt_off" value
> to indicate if running in the init path, since this value is only set
> during init.
>
> Fixes: a037f3ca0ea0 ("x86/mce/amd: Make threshold bank setting hotplug robust")
> Signed-off-by: Yazen Ghannam <[email protected]>
We want that in stable, right?
> ---
> arch/x86/kernel/cpu/mce/amd.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
> index 2eadc7c4c902..408c9546ea0b 100644
> --- a/arch/x86/kernel/cpu/mce/amd.c
> +++ b/arch/x86/kernel/cpu/mce/amd.c
> @@ -400,8 +400,12 @@ static void threshold_restart_bank(void *_tr)
> struct thresh_restart *tr = _tr;
> u32 hi, lo;
>
> - /* sysfs write might race against an offline operation */
> - if (this_cpu_read(threshold_banks))
> + /*
> + * sysfs write might race against an offline operation.
> + * Prevent register writes if threshold_banks are not set and this is
> + * not called from the init path as indicated by "set_lvt_off".
> + */
So if you convert this text into code, it would read like:
if (!this_cpu_read(threshold_banks) && !tr->set_lvt_off)
which is equivalent to:
> + if (!(this_cpu_read(threshold_banks) || tr->set_lvt_off))
but easier to follow, methinks.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Wed, Dec 29, 2021 at 06:42:18PM +0100, Borislav Petkov wrote:
> On Tue, Dec 07, 2021 at 07:30:28PM +0000, Yazen Ghannam wrote:
> > Changes to the AMD Thresholding sysfs code prevents sysfs writes from
> > updating the underlying registers once CPU init is completed, i.e.
> > "threshold_banks" is set.
> >
> > Allow the registers to be updated if the thresholding interface is
> > already initialized or if in the init path. Use the "set_lvt_off" value
> > to indicate if running in the init path, since this value is only set
> > during init.
> >
> > Fixes: a037f3ca0ea0 ("x86/mce/amd: Make threshold bank setting hotplug robust")
> > Signed-off-by: Yazen Ghannam <[email protected]>
>
> We want that in stable, right?
>
Yes, thanks for catching that.
> > ---
> > arch/x86/kernel/cpu/mce/amd.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
> > index 2eadc7c4c902..408c9546ea0b 100644
> > --- a/arch/x86/kernel/cpu/mce/amd.c
> > +++ b/arch/x86/kernel/cpu/mce/amd.c
> > @@ -400,8 +400,12 @@ static void threshold_restart_bank(void *_tr)
> > struct thresh_restart *tr = _tr;
> > u32 hi, lo;
> >
> > - /* sysfs write might race against an offline operation */
> > - if (this_cpu_read(threshold_banks))
> > + /*
> > + * sysfs write might race against an offline operation.
> > + * Prevent register writes if threshold_banks are not set and this is
> > + * not called from the init path as indicated by "set_lvt_off".
> > + */
>
> So if you convert this text into code, it would read like:
>
> if (!this_cpu_read(threshold_banks) && !tr->set_lvt_off)
>
> which is equivalent to:
>
> > + if (!(this_cpu_read(threshold_banks) || tr->set_lvt_off))
>
> but easier to follow, methinks.
>
Sure, I'll make the change and send another version.
Thanks,
Yazen