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SubjectRe: [PATCH] x86, pkeys: update documentation about availability

* Dave Hansen <> wrote:

> From: Dave Hansen <>
> Now that CPUs that implement Memory Protection Keys are publicly
> available we can be a bit less oblique about where it is available.
> Signed-off-by: Dave Hansen <>
> ---
> b/Documentation/x86/protection-keys.txt | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
> diff -puN Documentation/x86/protection-keys.txt~pkeys-update Documentation/x86/protection-keys.txt
> --- a/Documentation/x86/protection-keys.txt~pkeys-update 2017-11-09 10:36:53.381467202 -0800
> +++ b/Documentation/x86/protection-keys.txt 2017-11-09 10:43:15.527466249 -0800
> @@ -1,5 +1,10 @@
> -Memory Protection Keys for Userspace (PKU aka PKEYs) is a CPU feature
> -which will be found on future Intel CPUs.
> +Memory Protection Keys for Userspace (PKU aka PKEYs) is a feature
> +which is found on Intel's Skylake "Scalable Processor" Server CPUs.
> +It will be avalable in future non-server parts.
> +
> +For anyone wishing to test or use this feature, it is available in
> +Amazon's EC2 C5 instances and is known to work there using an Ubuntu
> +17.04 image.
> Memory Protection Keys provides a mechanism for enforcing page-based
> protections, but without requiring modification of the page tables

Could we please first fix the pkeys self-test? One of the testcases doesn't build
at all:

gcc -m32 -o /home/mingo/tip/tools/testing/selftests/x86/protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall -no-pie protection_keys.c -lrt -ldl -lm
In file included from /usr/include/signal.h:57:0,
from protection_keys.c:33:
protection_keys.c: In function ‘signal_handler’:
protection_keys.c:253:6: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’
before ‘.’ token
u64 si_pkey;

plus, on a related note, the MPX testcase produces annoying warnings:

gcc -m32 -o /home/mingo/tip/tools/testing/selftests/x86/mpx-mini-test_32 -O2 -g -std=gnu99 -pthread -Wall -no-pie mpx-mini-test.c -lrt -ldl -lm
mpx-mini-test.c: In function ‘insn_test_failed’:
mpx-mini-test.c:1406:3: warning: array subscript is above array bounds
printf("bte[1]: %lx\n", bte->contents[1]);
mpx-mini-test.c:1407:3: warning: array subscript is above array bounds
printf("bte[2]: %lx\n", bte->contents[2]);
mpx-mini-test.c:1408:3: warning: array subscript is above array bounds
printf("bte[3]: %lx\n", bte->contents[3]);



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