Re: [PATCH] arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup

On Thu, May 06, 2021 at 08:37:25PM -0700, Peter Collingbourne wrote:

A valid implementation choice for the ChooseRandomNonExcludedTag()
pseudocode function used by IRG is to behave in the same way as with
GCR_EL1.RRND=0. This would mean that RGSR_EL1.SEED is used as an LFSR
which must have a non-zero value in order for IRG to properly produce
pseudorandom numbers. However, RGSR_EL1 is reset to an UNKNOWN value
on soft reset and thus may reset to 0. Therefore we must initialize
RGSR_EL1.SEED to a non-zero value in order to ensure that IRG behaves
as expected.

Signed-off-by: Peter Collingbourne <redacted>
Cc: stable@vger.kernel.org

Rather than a generic cc stable that goes all the way to 4.4, please
add:

Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration")
Cc: <redacted> # 5.10.x

Thanks.

-- 
Catalin

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