Allow systems with mismatched 32-bit support at EL0 to run 32-bit
applications based on a new kernel parameter.
Signed-off-by: Will Deacon <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
arch/arm64/kernel/cpufeature.c | 7 +++++++
2 files changed, 14 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..f20188c44d83 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -289,6 +289,13 @@
do not want to use tracing_snapshot_alloc() as it needs
to be done where GFP_KERNEL allocations are allowed.
+ allow_mismatched_32bit_el0 [ARM64]
+ Allow execve() of 32-bit applications and setting of the
+ PER_LINUX32 personality on systems where only a strict
+ subset of the CPUs support 32-bit EL0. When this
+ parameter is present, the set of CPUs supporting 32-bit
+ EL0 is indicated by /sys/devices/system/cpu/aarch32_el0.
+
amd_iommu= [HW,X86-64]
Pass parameters to the AMD IOMMU driver in the system.
Possible values are:
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 534f80edb594..29017cbb6c8e 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1273,6 +1273,13 @@ const struct cpumask *system_32bit_el0_cpumask(void)
return cpu_possible_mask;
}
+static int __init parse_32bit_el0_param(char *str)
+{
+ allow_mismatched_32bit_el0 = true;
+ return 0;
+}
+early_param("allow_mismatched_32bit_el0", parse_32bit_el0_param);
+
static ssize_t aarch32_el0_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
--
2.29.2.454.gaff20da3a2-goog
On 11/24/20 15:50, Will Deacon wrote:
> Allow systems with mismatched 32-bit support at EL0 to run 32-bit
> applications based on a new kernel parameter.
>
> Signed-off-by: Will Deacon <[email protected]>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
> arch/arm64/kernel/cpufeature.c | 7 +++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 526d65d8573a..f20188c44d83 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -289,6 +289,13 @@
> do not want to use tracing_snapshot_alloc() as it needs
> to be done where GFP_KERNEL allocations are allowed.
>
> + allow_mismatched_32bit_el0 [ARM64]
> + Allow execve() of 32-bit applications and setting of the
> + PER_LINUX32 personality on systems where only a strict
> + subset of the CPUs support 32-bit EL0. When this
> + parameter is present, the set of CPUs supporting 32-bit
> + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0.
Shouldn't we document that a randomly selected 32-bit CPU will be prevented
from being hotplugged out all the time to act as the last man standing for any
currently running 32-bit application.
That was a mouthful! I'm sure you can phrase it better :-)
If we make this the last patch as it was before adding affinity handling, we
can drop patch 4 more easily I think?
Thanks
--
Qais Yousef
On Fri, Nov 27, 2020 at 01:17:59PM +0000, Qais Yousef wrote:
> On 11/24/20 15:50, Will Deacon wrote:
> > Allow systems with mismatched 32-bit support at EL0 to run 32-bit
> > applications based on a new kernel parameter.
> >
> > Signed-off-by: Will Deacon <[email protected]>
> > ---
> > Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
> > arch/arm64/kernel/cpufeature.c | 7 +++++++
> > 2 files changed, 14 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 526d65d8573a..f20188c44d83 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -289,6 +289,13 @@
> > do not want to use tracing_snapshot_alloc() as it needs
> > to be done where GFP_KERNEL allocations are allowed.
> >
> > + allow_mismatched_32bit_el0 [ARM64]
> > + Allow execve() of 32-bit applications and setting of the
> > + PER_LINUX32 personality on systems where only a strict
> > + subset of the CPUs support 32-bit EL0. When this
> > + parameter is present, the set of CPUs supporting 32-bit
> > + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0.
>
> Shouldn't we document that a randomly selected 32-bit CPU will be prevented
> from being hotplugged out all the time to act as the last man standing for any
> currently running 32-bit application.
>
> That was a mouthful! I'm sure you can phrase it better :-)
Sure, I'll have a go at adding something. Thanks.
> If we make this the last patch as it was before adding affinity handling, we
> can drop patch 4 more easily I think?
I'd still prefer to keep patch 4, but I can certainly try to move this one
later in the series.
Will