From: Mark Rutland <mark.rutland@arm.com>
To: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>,
Marc Zyngier <maz@kernel.org>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: Buggy branch in __init_el2_gicv3?
Date: Mon, 14 Feb 2022 14:56:42 +0000 [thread overview]
Message-ID: <YgptqviZbdXtaNH6@FVFF77S0Q05N> (raw)
In-Reply-To: <cac157d3b5e5d3df5d4d5c1bfe1d4132f7db5f53.camel@infinera.com>
On Mon, Feb 14, 2022 at 12:34:12PM +0000, Joakim Tjernlund wrote:
> In init_el2_state calls __init_el2_gicv3 which looks:
>
> /* GICv3 system register access */
> .macro __init_el2_gicv3
> mrs x0, id_aa64pfr0_el1
> ubfx x0, x0, #ID_AA64PFR0_GIC_SHIFT, #4
> cbz x0, .Lskip_gicv3_\@
>
> mrs_s x0, SYS_ICC_SRE_EL2
> orr x0, x0, #ICC_SRE_EL2_SRE // Set ICC_SRE_EL2.SRE==1
> orr x0, x0, #ICC_SRE_EL2_ENABLE // Set ICC_SRE_EL2.Enable==1
> msr_s SYS_ICC_SRE_EL2, x0
> isb // Make sure SRE is now set
> mrs_s x0, SYS_ICC_SRE_EL2 // Read SRE back,
> tbz x0, #0, 1f
> // tbz x0, #0, .Lskip_gicv3_\@ // and check that it sticks
> msr_s SYS_ICH_HCR_EL2, xzr // Reset ICC_HCR_EL2 to defaults
> .Lskip_gicv3_\@:
> .endm
>
> Note the tbz x0, #0, 1f, this instruction causes my A53 CPU to jump far out of the macro and make the
> CPU go into EL0, failing with an exception a bit later. I believe the 1f is a bug and if I replace it with
> tbz x0, #0, .Lskip_gicv3_\@
> the CPU continue too boot.
You're right, that should be targetting `.Lskip_gicv3_\@`. It looks like that
was left behind in commit:
114945d84a30a5fe ("arm64: Fix labels in el2_setup macros")
Marc?
> Why this is trigged is still a mystery to me, any pointers welcome :)
I believe this happens if EL3 has ICC_SRE_EL3.SRE == 0b0; in that case
ICC_SRE_EL2.SRE is RAZ/WI. i.e. your EL3 firmware isn't using GICv3 and hasn't
enabled it for lower ELs.
Thanks,
Mark.
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next prev parent reply other threads:[~2022-02-14 14:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 12:34 Buggy branch in __init_el2_gicv3? Joakim Tjernlund
2022-02-14 14:56 ` Mark Rutland [this message]
2022-02-14 15:14 ` Joakim Tjernlund
2022-02-14 17:16 ` Marc Zyngier
2022-02-14 16:26 ` Marc Zyngier
2022-02-14 17:12 ` Joakim Tjernlund
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