From: "André Przywara" <andre.przywara@arm.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>,
Mark Rutland <Mark.Rutland@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [boot-wrapper][PATCH] aarch64: Enable SPE for the non-secure world
Date: Thu, 6 Aug 2020 11:42:51 +0100 [thread overview]
Message-ID: <3123be0d-2536-473f-8918-bf3e9a75979b@arm.com> (raw)
In-Reply-To: <20200731094443.11564-1-alexandru.elisei@arm.com>
On 31/07/2020 10:44, Alexandru Elisei wrote:
Hi,
> MDCR_EL3.NSPB resets to an UNKNOWN value. Configure it to allow the
> profiling buffer to use non-secure memory and to permit direct register
> accesses from the non-secure world.
>
> So far, we haven't programmed MDCR_EL3 explicitly even though there are
> other fields which reset to an UNKNOWN value. The majority of those, when
> cleared, allow lower exception levels to use the features they control; for
> the other fields we don't have support yet. Reset the register to zero
> with the exception of MDCR_EL3.NSPB.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> Tested on the model, with ARMv8.2 enabled and disabled (no SPE present).
>
> arch/aarch64/boot.S | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
> index 74705cded338..f821b0175d4b 100644
> --- a/arch/aarch64/boot.S
> +++ b/arch/aarch64/boot.S
> @@ -55,6 +55,17 @@ _start:
>
> msr cptr_el3, xzr // Disable copro. traps to EL3
>
> + mov x0, xzr
> + mrs x1, id_aa64dfr0_el1
> + ubfx x1, x1, #32, #4
> + cbz x1, 1f
> +
> + // Enable SPE for the non-secure world.
> + ldr x1, =(0x3 << 12)
> + orr x0, x0, x1
Just a nit, but 0x3000 is one of the (few) immediate patterns that can
be encoded directly in ORR. So you can save the ldr.
Other than that:
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Cheers,
Andre
> +
> +1: msr mdcr_el3, x0 // Disable traps to EL3
> +
> mrs x0, id_aa64pfr0_el1
> ubfx x0, x0, #32, #4 // SVE present?
> cbz x0, 1f // Skip SVE init if not
>
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next prev parent reply other threads:[~2020-08-06 12:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 9:44 [boot-wrapper][PATCH] aarch64: Enable SPE for the non-secure world Alexandru Elisei
2020-08-06 10:42 ` André Przywara [this message]
2020-08-12 12:10 ` Mark Rutland
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