linux-kernel - Re: [PATCH] x86, pkeys: update documentation about availability

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Date:   Fri, 10 Nov 2017 07:12:04 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86, pkeys: update documentation about availability


* Dave Hansen <dave.hansen@...ux.intel.com> wrote:

> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> 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 <dave.hansen@...ux.intel.com>
> ---
> 
>  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 
 [-Warray-bounds]
    printf("bte[1]: %lx\n", bte->contents[1]);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 mpx-mini-test.c:1407:3: warning: array subscript is above array bounds 
 [-Warray-bounds]
    printf("bte[2]: %lx\n", bte->contents[2]);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 mpx-mini-test.c:1408:3: warning: array subscript is above array bounds 
 [-Warray-bounds]
    printf("bte[3]: %lx\n", bte->contents[3]);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks,

	Ingo