[v4] Fix Guest random crash on Cortex-N1/A76/A75 cores

[PATCH v4 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

Posted by Wei Chen 5 years, 5 months ago

Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
FP/SIMD implementations. Currently, we exactly know the meaning of
0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
features presented. If there is a value 0x2 bumped in the future,
Xen behaviors for value <= 0x1 can also take effect. But what Xen
done for value <= 0x1 may not always cover new value 0x2 required.
We throw these messages to break the silence when Xen detected
unknown FP/SIMD IDs to notice user to check.

Signed-off-by: Wei Chen <wei.chen@arm.com>
---
 xen/arch/arm/setup.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 7968cee47d..6a31eca984 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -133,6 +133,18 @@ static void __init processor_id(void)
            cpu_has_simd ? " AdvancedSIMD" : "",
            cpu_has_gicv3 ? " GICv3-SysReg" : "");
 
+    /* Warn user if we find unknown floating-point features */
+    if ( cpu_has_fp && (boot_cpu_feature64(fp) >= 2) )
+        printk(XENLOG_WARNING "WARNING: Unknown Floating-point ID:%d, "
+               "this may result to corruption on the platform\n",
+               boot_cpu_feature64(fp));
+
+    /* Warn user if we find unknown AdvancedSIMD features */
+    if ( cpu_has_simd && (boot_cpu_feature64(simd) >= 2) )
+        printk(XENLOG_WARNING "WARNING: Unknown AdvancedSIMD ID:%d, "
+               "this may result to corruption on the platform\n",
+               boot_cpu_feature64(simd));
+
     printk("  Debug Features: %016"PRIx64" %016"PRIx64"\n",
            boot_cpu_data.dbg64.bits[0], boot_cpu_data.dbg64.bits[1]);
     printk("  Auxiliary Features: %016"PRIx64" %016"PRIx64"\n",
-- 
2.17.1

Re: [PATCH v4 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

Posted by Bertrand Marquis 5 years, 5 months ago


> On 25 Aug 2020, at 17:06, Wei Chen <Wei.Chen@arm.com> wrote:
> 
> Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
> FP/SIMD implementations. Currently, we exactly know the meaning of
> 0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
> features presented. If there is a value 0x2 bumped in the future,
> Xen behaviors for value <= 0x1 can also take effect. But what Xen
> done for value <= 0x1 may not always cover new value 0x2 required.
> We throw these messages to break the silence when Xen detected
> unknown FP/SIMD IDs to notice user to check.
> 
> Signed-off-by: Wei Chen <wei.chen@arm.com>

With the small typo after fixed:
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

> ---
> xen/arch/arm/setup.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 7968cee47d..6a31eca984 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -133,6 +133,18 @@ static void __init processor_id(void)
>            cpu_has_simd ? " AdvancedSIMD" : "",
>            cpu_has_gicv3 ? " GICv3-SysReg" : "");
> 
> +    /* Warn user if we find unknown floating-point features */
> +    if ( cpu_has_fp && (boot_cpu_feature64(fp) >= 2) )
> +        printk(XENLOG_WARNING "WARNING: Unknown Floating-point ID:%d, "
> +               "this may result to corruption on the platform\n",

s/to/in/

> +               boot_cpu_feature64(fp));
> +
> +    /* Warn user if we find unknown AdvancedSIMD features */
> +    if ( cpu_has_simd && (boot_cpu_feature64(simd) >= 2) )
> +        printk(XENLOG_WARNING "WARNING: Unknown AdvancedSIMD ID:%d, "
> +               "this may result to corruption on the platform\n",

same as upper

> +               boot_cpu_feature64(simd));
> +
>     printk("  Debug Features: %016"PRIx64" %016"PRIx64"\n",
>            boot_cpu_data.dbg64.bits[0], boot_cpu_data.dbg64.bits[1]);
>     printk("  Auxiliary Features: %016"PRIx64" %016"PRIx64"\n",
> -- 
> 2.17.1
>

RE: [PATCH v4 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

Posted by Wei Chen 5 years, 5 months ago

Hi Bertand,

> -----Original Message-----
> From: Bertrand Marquis <Bertrand.Marquis@arm.com>
> Sent: 2020年8月27日 22:13
> To: Wei Chen <Wei.Chen@arm.com>
> Cc: Xen-devel <xen-devel@lists.xenproject.org>; sstabellini@kernel.org;
> julien@xen.org; Andre Przywara <Andre.Przywara@arm.com>; Penny Zheng
> <Penny.Zheng@arm.com>; Kaly Xin <Kaly.Xin@arm.com>; nd <nd@arm.com>
> Subject: Re: [PATCH v4 2/2] xen/arm: Throw messages for unknown
> FP/SIMD implement ID
> 
> 
> 
> > On 25 Aug 2020, at 17:06, Wei Chen <Wei.Chen@arm.com> wrote:
> >
> > Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
> > FP/SIMD implementations. Currently, we exactly know the meaning of
> > 0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
> > features presented. If there is a value 0x2 bumped in the future,
> > Xen behaviors for value <= 0x1 can also take effect. But what Xen
> > done for value <= 0x1 may not always cover new value 0x2 required.
> > We throw these messages to break the silence when Xen detected
> > unknown FP/SIMD IDs to notice user to check.
> >
> > Signed-off-by: Wei Chen <wei.chen@arm.com>
> 
> With the small typo after fixed:
> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
> 
> > ---
> > xen/arch/arm/setup.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> > index 7968cee47d..6a31eca984 100644
> > --- a/xen/arch/arm/setup.c
> > +++ b/xen/arch/arm/setup.c
> > @@ -133,6 +133,18 @@ static void __init processor_id(void)
> >            cpu_has_simd ? " AdvancedSIMD" : "",
> >            cpu_has_gicv3 ? " GICv3-SysReg" : "");
> >
> > +    /* Warn user if we find unknown floating-point features */
> > +    if ( cpu_has_fp && (boot_cpu_feature64(fp) >= 2) )
> > +        printk(XENLOG_WARNING "WARNING: Unknown Floating-point
> ID:%d, "
> > +               "this may result to corruption on the platform\n",
> 
> s/to/in/
> 
> > +               boot_cpu_feature64(fp));
> > +
> > +    /* Warn user if we find unknown AdvancedSIMD features */
> > +    if ( cpu_has_simd && (boot_cpu_feature64(simd) >= 2) )
> > +        printk(XENLOG_WARNING "WARNING: Unknown AdvancedSIMD
> ID:%d, "
> > +               "this may result to corruption on the platform\n",
> 
> same as upper

I would fix above two typos and send a new version.

> 
> > +               boot_cpu_feature64(simd));
> > +
> >     printk("  Debug Features: %016"PRIx64" %016"PRIx64"\n",
> >            boot_cpu_data.dbg64.bits[0], boot_cpu_data.dbg64.bits[1]);
> >     printk("  Auxiliary Features: %016"PRIx64" %016"PRIx64"\n",
> > --
> > 2.17.1
> >
> 
>

Re: [PATCH v4 2/2] xen/arm: Throw messages for unknown FP/SIMD implement ID

Posted by Julien Grall 5 years, 5 months ago

Hi,

On 25/08/2020 17:06, Wei Chen wrote:
> Arm ID_AA64PFR0_EL1 register provides two fields to describe CPU
> FP/SIMD implementations. Currently, we exactly know the meaning of
> 0x0, 0x1 and 0xf of these fields. Xen treats value < 8 as FP/SIMD
> features presented. If there is a value 0x2 bumped in the future,
> Xen behaviors for value <= 0x1 can also take effect. But what Xen
> done for value <= 0x1 may not always cover new value 0x2 required.
> We throw these messages to break the silence when Xen detected
> unknown FP/SIMD IDs to notice user to check.
> 
> Signed-off-by: Wei Chen <wei.chen@arm.com>

Acked-by: Julien Grall <jgrall@amazon.com>

Cheers,

-- 
Julien Grall