linux-kernel - [PATCH] arm64: Disable EL2 traps for BRBE instructions executed in EL1

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Message-Id: <20230324055127.2228330-1-anshuman.khandual@arm.com>
Date:   Fri, 24 Mar 2023 11:21:27 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Mark Brown <broonie@...nel.org>,
        Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: Disable EL2 traps for BRBE instructions executed in EL1

This disables EL2 traps for BRBE instructions executed in EL1. This would
enable BRBE to be configured and used successfully in the guest kernel.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Mark Brown <broonie@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
This patch applies on v6.3-rc3, after the following patch series from Mark

https://lore.kernel.org/all/20230306-arm64-fgt-reg-gen-v3-0-decba93cbaab@kernel.org/

 arch/arm64/include/asm/el2_setup.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index 037724b19c5c..06bf321a17be 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -161,6 +161,16 @@
 	msr_s	SYS_HFGWTR_EL2, x0
 	msr_s	SYS_HFGITR_EL2, xzr
 
+	mrs	x1, id_aa64dfr0_el1
+	ubfx	x1, x1, #ID_AA64DFR0_EL1_BRBE_SHIFT, #4
+	cbz	x1, .Lskip_brbe_\@
+
+	mov	x0, xzr
+	orr	x0, x0, #HFGITR_EL2_nBRBIALL
+	orr	x0, x0, #HFGITR_EL2_nBRBINJ
+	msr_s	SYS_HFGITR_EL2, x0
+
+.Lskip_brbe_\@:
 	mrs	x1, id_aa64pfr0_el1		// AMU traps UNDEF without AMU
 	ubfx	x1, x1, #ID_AA64PFR0_EL1_AMU_SHIFT, #4
 	cbz	x1, .Lskip_fgt_\@
-- 
2.25.1