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Date: Sun, 21 Jan 2024 14:31:53 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Audra Mitchell <audra@redhat.com>
Cc: shuah@kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, raquini@redhat.com, Adam Sindelar
 <adam@wowsignal.io>
Subject: Re: [PATCH] selftests/mm: Update va_high_addr_switch.sh to check
 CPU for la57 flag
Message-Id: <20240121143153.5dcfe26dea53ba0e896dbf85@linux-foundation.org>
In-Reply-To: <20240119205801.62769-1-audra@redhat.com>
References: <20240119205801.62769-1-audra@redhat.com>
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On Fri, 19 Jan 2024 15:58:01 -0500 Audra Mitchell <audra@redhat.com> wrote:

> In order for the page table level 5 to be in use, the CPU must have the
> setting enabled in addition to the CONFIG option. Check for the flag to be
> set to avoid false test failures on systems that do not have this cpu flag
> set.
> 

Thanks.

I'll add

Cc: Adam Sindelar <adam@wowsignal.io>
Fixes: 4f2930c6718a ("selftests/vm: only run 128TBswitch with 5-level paging")
Cc: <stable@vger.kernel.org>

A more complete description of these "test failures" would be helpful
please.

> --- a/tools/testing/selftests/mm/va_high_addr_switch.sh
> +++ b/tools/testing/selftests/mm/va_high_addr_switch.sh
> @@ -29,9 +29,15 @@ check_supported_x86_64()
>  	# See man 1 gzip under '-f'.
>  	local pg_table_levels=$(gzip -dcfq "${config}" | grep PGTABLE_LEVELS | cut -d'=' -f 2)
>  
> +	local cpu_supports_pl5=$(awk '/^flags/ {if (/la57/) {print 0;}
> +		else {print 1}; exit}' /proc/cpuinfo 2>/dev/null)
> +
>  	if [[ "${pg_table_levels}" -lt 5 ]]; then
>  		echo "$0: PGTABLE_LEVELS=${pg_table_levels}, must be >= 5 to run this test"
>  		exit $ksft_skip
> +	elif [[ "${cpu_supports_pl5}" -ne 0 ]]; then
> +		echo "$0: CPU does not have the necessary la57 flag to support page table level 5"
> +		exit $ksft_skip
>  	fi
>  }
>  
> -- 
> 2.43.0