On Wed, Apr 13, 2022, Ben Gardon wrote:
> There's currently no test coverage of NX hugepages in KVM selftests, so
> add a basic test to ensure that the feature works as intended.
...
> diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> new file mode 100644
> index 000000000000..7f80e48781fd
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> @@ -0,0 +1,166 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * tools/testing/selftests/kvm/nx_huge_page_test.c
> + *
> + * Usage: to be run via nx_huge_page_test.sh, which does the necessary
> + * environment setup and teardown
It would be really nice if this test could either (a) do something useful without
having to manually set /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages,
or (b) refuse to run unless it's (likely) been invoked by the script. E.g. maybe
add a magic token that must be passed in? That way just running the bare test
will provide a helpful skip message, but someone that wants to fiddle with it can
still run it manually.
> +int main(int argc, char **argv)
> +{
> + struct kvm_vm *vm;
> + struct timespec ts;
> + void *hva;
This needs to check if the workaround is actually enabled via module param. Not
as big a deal if there's a magic number, but it's also not too hard to query a
module param. Or at least, it shouldn't be, I'm fairly certain that's one of the
things I want to address in the selftests overhaul.
Aha! Actually, IIUC, the patch that validates the per-VM override adds full support
for the module param being turned off.
So, how about pull in the tweaks to the expected number to this patch, and then
the per-VM override test just makes disable_nx a logical OR of the module param
beyond off or the test using the per-VM override.
> diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> new file mode 100755
> index 000000000000..19fc95723fcb
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> @@ -0,0 +1,25 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0-only */
> +
> +# tools/testing/selftests/kvm/nx_huge_page_test.sh
> +# Copyright (C) 2022, Google LLC.
This should either check for root or use sudo.
> +NX_HUGE_PAGES=$(cat /sys/module/kvm/parameters/nx_huge_pages)
> +NX_HUGE_PAGES_RECOVERY_RATIO=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio)
> +NX_HUGE_PAGES_RECOVERY_PERIOD=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms)
> +HUGE_PAGES=$(cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages)
> +
> +echo 1 > /sys/module/kvm/parameters/nx_huge_pages
> +echo 1 > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> +echo 100 > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> +echo 200 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> +
> +./nx_huge_pages_test
I would much prefer this find its path and use that to reference the test, e.g. this
fails if invoking the script from anything but the x86_64 subdirectory. I'd provide
a snippet of how to do that, but my scripting skills are garbage :-)
> +RET=$?
> +
> +echo $NX_HUGE_PAGES > /sys/module/kvm/parameters/nx_huge_pages
> +echo $NX_HUGE_PAGES_RECOVERY_RATIO > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> +echo $NX_HUGE_PAGES_RECOVERY_PERIOD > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> +echo $HUGE_PAGES > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> +
> +exit $RET
> --
> 2.35.1.1178.g4f1659d476-goog
>
On Wed, Apr 13, 2022 at 3:35 PM Sean Christopherson <[email protected]> wrote:
>
> On Wed, Apr 13, 2022, Ben Gardon wrote:
> > There's currently no test coverage of NX hugepages in KVM selftests, so
> > add a basic test to ensure that the feature works as intended.
>
> ...
>
> > diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> > new file mode 100644
> > index 000000000000..7f80e48781fd
> > --- /dev/null
> > +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> > @@ -0,0 +1,166 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * tools/testing/selftests/kvm/nx_huge_page_test.c
> > + *
> > + * Usage: to be run via nx_huge_page_test.sh, which does the necessary
> > + * environment setup and teardown
>
> It would be really nice if this test could either (a) do something useful without
> having to manually set /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages,
> or (b) refuse to run unless it's (likely) been invoked by the script. E.g. maybe
> add a magic token that must be passed in? That way just running the bare test
> will provide a helpful skip message, but someone that wants to fiddle with it can
> still run it manually.
>
> > +int main(int argc, char **argv)
> > +{
> > + struct kvm_vm *vm;
> > + struct timespec ts;
> > + void *hva;
>
> This needs to check if the workaround is actually enabled via module param. Not
> as big a deal if there's a magic number, but it's also not too hard to query a
> module param. Or at least, it shouldn't be, I'm fairly certain that's one of the
> things I want to address in the selftests overhaul.
>
> Aha! Actually, IIUC, the patch that validates the per-VM override adds full support
> for the module param being turned off.
>
> So, how about pull in the tweaks to the expected number to this patch, and then
> the per-VM override test just makes disable_nx a logical OR of the module param
> beyond off or the test using the per-VM override.
>
> > diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> > new file mode 100755
> > index 000000000000..19fc95723fcb
> > --- /dev/null
> > +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> > @@ -0,0 +1,25 @@
> > +#!/bin/bash
> > +# SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +# tools/testing/selftests/kvm/nx_huge_page_test.sh
> > +# Copyright (C) 2022, Google LLC.
>
> This should either check for root or use sudo.
Is there not any scenario where the below setup commands could work
without root?
>
> > +NX_HUGE_PAGES=$(cat /sys/module/kvm/parameters/nx_huge_pages)
> > +NX_HUGE_PAGES_RECOVERY_RATIO=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio)
> > +NX_HUGE_PAGES_RECOVERY_PERIOD=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms)
> > +HUGE_PAGES=$(cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages)
> > +
> > +echo 1 > /sys/module/kvm/parameters/nx_huge_pages
> > +echo 1 > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> > +echo 100 > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> > +echo 200 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> > +
> > +./nx_huge_pages_test
>
> I would much prefer this find its path and use that to reference the test, e.g. this
> fails if invoking the script from anything but the x86_64 subdirectory. I'd provide
> a snippet of how to do that, but my scripting skills are garbage :-)
>
> > +RET=$?
> > +
> > +echo $NX_HUGE_PAGES > /sys/module/kvm/parameters/nx_huge_pages
> > +echo $NX_HUGE_PAGES_RECOVERY_RATIO > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> > +echo $NX_HUGE_PAGES_RECOVERY_PERIOD > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> > +echo $HUGE_PAGES > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> > +
> > +exit $RET
> > --
> > 2.35.1.1178.g4f1659d476-goog
> >
On Thu, Apr 14, 2022, Ben Gardon wrote:
> On Wed, Apr 13, 2022 at 3:35 PM Sean Christopherson <[email protected]> wrote:
> > > diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> > > new file mode 100755
> > > index 000000000000..19fc95723fcb
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> > > @@ -0,0 +1,25 @@
> > > +#!/bin/bash
> > > +# SPDX-License-Identifier: GPL-2.0-only */
> > > +
> > > +# tools/testing/selftests/kvm/nx_huge_page_test.sh
> > > +# Copyright (C) 2022, Google LLC.
> >
> > This should either check for root or use sudo.
>
> Is there not any scenario where the below setup commands could work
> without root?
Technically, yes, someone could be running the test as a non-root user with
the necessary permissions. Practically speaking, I would be surprised if anyone
configures module params in that way.
That said, there's certainly no harm in using sudo as a fall back.