On 06/02/2019 19:24, Jeremy Linton wrote:

Hi,


I just realized I replied to this off-list.

On 01/30/2019 12:02 PM, Andre Przywara wrote:

quoted

On Fri, 25 Jan 2019 12:07:00 -0600
Jeremy Linton [off-list ref] wrote:

Hi,

quoted

For a while Arm64 has been capable of force enabling
or disabling the kpti mitigations. Lets make sure the
documentation reflects that.

Signed-off-by: Jeremy Linton <redacted>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
---
  Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt

b/Documentation/admin-guide/kernel-parameters.txt index
b799bcf67d7b..9475f02c79da 100644 ---
a/Documentation/admin-guide/kernel-parameters.txt +++
b/Documentation/admin-guide/kernel-parameters.txt @@ -1982,6 +1982,12

@@ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,

              the default is off.
  +    kpti=        [ARM64] Control page table isolation of
user
+            and kernel address spaces.
+            Default: enabled on cores which need
mitigation.

Would this be a good place to mention that we enable it when
CONFIG_RANDOMIZE_BASE is enabled and we have a valid kaslr_offset? I
found this somewhat surprising, also it's unrelated to the
vulnerability.

Maybe, but I tend to think since this command line forces it on/off
regardless of RANDOMIZE_BASE, that a better place to mention that
RANDOMIZE_BASE forces kpti on is the Kconfig option.

True, kpti= takes precedence, in both ways. Disregard my comment then,
this is indeed not the right place to mention RANDOMIZE_BASE.

Cheers,
Andre.

BTW: Thanks for reviewing this.

quoted

Cheers,
Andre

quoted

+            0: force disabled
+            1: force enabled
+
      kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled
MSRs. Default is 0 (don't ignore, but inject #GP)
  

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