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

[Anshuman Khandual]

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 at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Mark Brown <broonie at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual at arm.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