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From: Michael Ellerman <mpe@ellerman.id.au>
To: Sandipan Das <sandipan@linux.ibm.com>,
	shuahkh@osg.samsung.com, linux-kselftest@vger.kernel.org
Cc: linux-arch@vger.kernel.org, fweimer@redhat.com,
	linux-mm@kvack.org, aneesh.kumar@linux.ibm.com, x86@kernel.org,
	linuxram@us.ibm.com, mhocko@kernel.org, dave.hansen@intel.com,
	mingo@redhat.com, msuchanek@suse.de,
	linuxppc-dev@lists.ozlabs.org, bauerman@linux.ibm.com
Subject: Re: [PATCH v15 14/23] selftests/vm/pkeys: Fix assertion in test_pkey_alloc_exhaust()
Date: Wed, 15 Jan 2020 17:30:01 +1000
Message-ID: <87a76p9nye.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <d82e1652135569cfc38b289f88e39e94d55308ff.1576645161.git.sandipan@linux.ibm.com>

Sandipan Das <sandipan@linux.ibm.com> writes:
> From: Ram Pai <linuxram@us.ibm.com>
>
> Some pkeys which are valid on the hardware are reserved
> and not available for application use. These keys cannot
> be allocated.
>
> test_pkey_alloc_exhaust() tries to account for these and
> has an assertion which validates if all available pkeys
> have been exahaustively allocated. However, the expression
> that is currently used is only valid for x86. On powerpc,
> a pkey is additionally reserved as compared to x86. Hence,
> the assertion is made to use an arch-specific helper to
> get the correct count of reserved pkeys.

The number of reserved keys is at the whim of the
firmware/hypervisor/kernel.

I'm not sure it makes sense to test this exhaustion behaviour, it's
likely going to break in future.

If you do want to test it you should at least move patch 21 prior to
this one.

cheers

> cc: Dave Hansen <dave.hansen@intel.com>
> cc: Florian Weimer <fweimer@redhat.com>
> Signed-off-by: Ram Pai <linuxram@us.ibm.com>
> Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
> ---
>  tools/testing/selftests/vm/protection_keys.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
> index 1920bca84def..8d90cfe2c9bd 100644
> --- a/tools/testing/selftests/vm/protection_keys.c
> +++ b/tools/testing/selftests/vm/protection_keys.c
> @@ -1152,6 +1152,7 @@ void test_pkey_alloc_exhaust(int *ptr, u16 pkey)
>  	dprintf3("%s()::%d\n", __func__, __LINE__);
>  
>  	/*
> +	 * On x86:
>  	 * There are 16 pkeys supported in hardware.  Three are
>  	 * allocated by the time we get here:
>  	 *   1. The default key (0)
> @@ -1159,8 +1160,16 @@ void test_pkey_alloc_exhaust(int *ptr, u16 pkey)
>  	 *   3. One allocated by the test code and passed in via
>  	 *      'pkey' to this function.
>  	 * Ensure that we can allocate at least another 13 (16-3).
> +	 *
> +	 * On powerpc:
> +	 * There are either 5 or 32 pkeys supported in hardware
> +	 * depending on the page size (4K or 64K). Four are
> +	 * allocated by the time we get here. This includes
> +	 * pkey-0, pkey-1, exec-only pkey and the one allocated
> +	 * by the test code.
> +	 * Ensure that we can allocate the remaining.
>  	 */
> -	pkey_assert(i >= NR_PKEYS-3);
> +	pkey_assert(i >= (NR_PKEYS - get_arch_reserved_keys() - 1));
>  
>  	for (i = 0; i < nr_allocated_pkeys; i++) {
>  		err = sys_pkey_free(allocated_pkeys[i]);
> -- 
> 2.17.1

  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18  7:51 [PATCH v15 00/24] selftests, powerpc, x86: Memory Protection Keys Sandipan Das
2019-12-18  7:51 ` [PATCH v15 01/23] selftests/x86/pkeys: Move selftests to arch-neutral directory Sandipan Das
2019-12-18  7:51 ` [PATCH v15 02/23] selftests/vm/pkeys: Rename all references to pkru to a generic name Sandipan Das
2019-12-18  7:51 ` [PATCH v15 03/23] selftests/vm/pkeys: Move generic definitions to header file Sandipan Das
2019-12-18  7:51 ` [PATCH v15 04/23] selftests/vm/pkeys: Move some definitions to arch-specific header Sandipan Das
2019-12-18  7:51 ` [PATCH v15 05/23] selftests/vm/pkeys: Make gcc check arguments of sigsafe_printf() Sandipan Das
2019-12-18  7:51 ` [PATCH v15 06/23] selftests/vm/pkeys: Typecast the pkey register Sandipan Das
2019-12-18 20:46   ` Dave Hansen
2019-12-18 20:59     ` Michal Suchánek
2019-12-18 21:01       ` Dave Hansen
2019-12-18 21:45         ` Michal Suchánek
2019-12-19 11:39         ` Michael Ellerman
2019-12-18  7:51 ` [PATCH v15 07/23] selftests: vm: pkeys: Add helpers for pkey bits Sandipan Das
2019-12-18  7:51 ` [PATCH v15 08/23] selftests/vm/pkeys: Fix pkey_disable_clear() Sandipan Das
2019-12-18  7:51 ` [PATCH v15 09/23] selftests/vm/pkeys: Fix assertion in pkey_disable_set/clear() Sandipan Das
2019-12-18  7:51 ` [PATCH v15 10/23] selftests/vm/pkeys: Fix alloc_random_pkey() to make it really random Sandipan Das
2019-12-18  7:51 ` [PATCH v15 11/23] selftests: vm: pkeys: Use the correct huge page size Sandipan Das
2019-12-18  7:51 ` [PATCH v15 12/23] selftests/vm/pkeys: Introduce generic pkey abstractions Sandipan Das
2019-12-18  7:51 ` [PATCH v15 13/23] selftests/vm/pkeys: Introduce powerpc support Sandipan Das
2019-12-18  7:51 ` [PATCH v15 14/23] selftests/vm/pkeys: Fix assertion in test_pkey_alloc_exhaust() Sandipan Das
2020-01-15  7:30   ` Michael Ellerman [this message]
2019-12-18  7:51 ` [PATCH v15 15/23] selftests/vm/pkeys: Improve checks to determine pkey support Sandipan Das
2019-12-18  7:51 ` [PATCH v15 16/23] selftests/vm/pkeys: Associate key on a mapped page and detect access violation Sandipan Das
2019-12-18  7:51 ` [PATCH v15 17/23] selftests/vm/pkeys: Associate key on a mapped page and detect write violation Sandipan Das
2019-12-18  7:51 ` [PATCH v15 18/23] selftests/vm/pkeys: Detect write violation on a mapped access-denied-key page Sandipan Das
2019-12-18  7:51 ` [PATCH v15 19/23] selftests/vm/pkeys: Introduce a sub-page allocator Sandipan Das
2019-12-18  7:51 ` [PATCH v15 20/23] selftests/vm/pkeys: Test correct behaviour of pkey-0 Sandipan Das
2019-12-18  7:51 ` [PATCH v15 21/23] selftests/vm/pkeys: Fix number of reserved powerpc pkeys Sandipan Das
2019-12-18  7:51 ` [PATCH v15 22/23] selftests/vm/pkeys: Override access right definitions on powerpc Sandipan Das
2019-12-18  7:51 ` [PATCH v15 23/23] selftests: vm: pkeys: Use the correct page size " Sandipan Das
2020-01-15  7:07   ` Michael Ellerman
2020-01-16  8:33     ` Sandipan Das
2019-12-18 20:48 ` [PATCH v15 00/24] selftests, powerpc, x86: Memory Protection Keys Dave Hansen
2020-01-10 17:38 ` Aneesh Kumar K.V
2020-01-10 17:57   ` Dave Hansen
2020-01-11 16:50     ` Sandipan Das

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