[PATCH V18 4/9] arm64/boot: Enable EL2 requirements for BRBE
From: Anshuman Khandual
Date: Thu Jun 13 2024 - 02:19:11 EST
Fine grained trap control for BRBE registers, and instructions access need
to be configured in HDFGRTR_EL2, HDFGWTR_EL2 and HFGITR_EL2 registers when
kernel enters at EL1 but EL2 is present. This changes __init_el2_fgt() as
required.
Similarly cycle and mis-prediction capture need to be enabled in BRBCR_EL1
and BRBCR_EL2 when the kernel enters either into EL1 or EL2. This adds new
__init_el2_brbe() to achieve this objective.
This also updates Documentation/arch/arm64/booting.rst with all the above
EL2 along with MDRC_EL3.SBRBE requirements.
First this replaces an existing hard encoding (1 << 62) with corresponding
applicable macro HDFGRTR_EL2_nPMSNEVFR_EL1_MASK.
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Oliver Upton <oliver.upton@xxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
----
Changes in V18:
- Dropped ifdef CONFIG_ARM64_BRBE around __init_el2_brbe()
- Updated the in code comment around __init_el2_brbe()
- Dropped the write up for EL2->EL1 transition, moved up the EL3 write up
Documentation/arch/arm64/booting.rst | 21 +++++++
arch/arm64/include/asm/el2_setup.h | 87 +++++++++++++++++++++++++++-
2 files changed, 105 insertions(+), 3 deletions(-)
diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst
index b57776a68f15..c8a17c021968 100644
--- a/Documentation/arch/arm64/booting.rst
+++ b/Documentation/arch/arm64/booting.rst
@@ -349,6 +349,27 @@ Before jumping into the kernel, the following conditions must be met:
- HWFGWTR_EL2.nSMPRI_EL1 (bit 54) must be initialised to 0b01.
+ For CPUs with feature Branch Record Buffer Extension (FEAT_BRBE):
+
+ - If EL3 is present:
+
+ - MDCR_EL3.SBRBE (bits 33:32) must be initialised to 0b11.
+
+ - If the kernel is entered at EL1 and EL2 is present:
+
+ - BRBCR_EL2.CC (bit 3) must be initialised to 0b1.
+ - BRBCR_EL2.MPRED (bit 4) must be initialised to 0b1.
+
+ - HDFGRTR_EL2.nBRBDATA (bit 61) must be initialised to 0b1.
+ - HDFGRTR_EL2.nBRBCTL (bit 60) must be initialised to 0b1.
+ - HDFGRTR_EL2.nBRBIDR (bit 59) must be initialised to 0b1.
+
+ - HDFGWTR_EL2.nBRBDATA (bit 61) must be initialised to 0b1.
+ - HDFGWTR_EL2.nBRBCTL (bit 60) must be initialised to 0b1.
+
+ - HFGITR_EL2.nBRBIALL (bit 56) must be initialised to 0b1.
+ - HFGITR_EL2.nBRBINJ (bit 55) must be initialised to 0b1.
+
For CPUs with the Scalable Matrix Extension FA64 feature (FEAT_SME_FA64):
- If EL3 is present:
diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index fd87c4b8f984..1c7b131ad2be 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -155,6 +155,40 @@
.Lskip_set_cptr_\@:
.endm
+/*
+ * Enable BRBE to record cycle counts and branch mispredicts.
+ *
+ * At any EL, to record cycle counts BRBE requires that both
+ * BRBCR_EL2.CC=1 and BRBCR_EL1.CC=1.
+ *
+ * At any EL, to record branch mispredicts BRBE requires that both
+ * BRBCR_EL2.MPRED=1 and BRBCR_EL1.MPRED=1.
+ *
+ * When HCR_EL2.E2H=1, the BRBCR_EL1 encoding is redirected to
+ * BRBCR_EL2, but the {CC,MPRED} bits in the real BRBCR_EL1 register
+ * still apply.
+ *
+ * Set {CC,MPRBED} in both BRBCR_EL2 and BRBCR_EL1 so that at runtime we
+ * only need to enable/disable thse in BRBCR_EL1 regardless of whether
+ * the kernel ends up executing in EL1 or EL2.
+ */
+.macro __init_el2_brbe
+ mrs x1, id_aa64dfr0_el1
+ ubfx x1, x1, #ID_AA64DFR0_EL1_BRBE_SHIFT, #4
+ cbz x1, .Lskip_brbe_\@
+
+ mov_q x0, BRBCR_ELx_CC | BRBCR_ELx_MPRED
+ msr_s SYS_BRBCR_EL2, x0
+
+ __check_hvhe .Lset_brbe_nvhe_\@, x1
+ msr_s SYS_BRBCR_EL12, x0 // VHE
+ b .Lskip_brbe_\@
+
+.Lset_brbe_nvhe_\@:
+ msr_s SYS_BRBCR_EL1, x0 // NVHE
+.Lskip_brbe_\@:
+.endm
+
/* Disable any fine grained traps */
.macro __init_el2_fgt
mrs x1, id_aa64mmfr0_el1
@@ -162,16 +196,48 @@
cbz x1, .Lskip_fgt_\@
mov x0, xzr
+ mov x2, xzr
mrs x1, id_aa64dfr0_el1
ubfx x1, x1, #ID_AA64DFR0_EL1_PMSVer_SHIFT, #4
cmp x1, #3
b.lt .Lset_debug_fgt_\@
+
/* Disable PMSNEVFR_EL1 read and write traps */
- orr x0, x0, #(1 << 62)
+ orr x0, x0, #HDFGRTR_EL2_nPMSNEVFR_EL1_MASK
+ orr x2, x2, #HDFGWTR_EL2_nPMSNEVFR_EL1_MASK
.Lset_debug_fgt_\@:
+#ifdef CONFIG_ARM64_BRBE
+ mrs x1, id_aa64dfr0_el1
+ ubfx x1, x1, #ID_AA64DFR0_EL1_BRBE_SHIFT, #4
+ cbz x1, .Lskip_brbe_reg_fgt_\@
+
+ /*
+ * Disable read traps for the following registers
+ *
+ * [BRBSRC|BRBTGT|RBINF]_EL1
+ * [BRBSRCINJ|BRBTGTINJ|BRBINFINJ|BRBTS]_EL1
+ */
+ orr x0, x0, #HDFGRTR_EL2_nBRBDATA_MASK
+
+ /*
+ * Disable write traps for the following registers
+ *
+ * [BRBSRCINJ|BRBTGTINJ|BRBINFINJ|BRBTS]_EL1
+ */
+ orr x2, x2, #HDFGWTR_EL2_nBRBDATA_MASK
+
+ /* Disable read and write traps for [BRBCR|BRBFCR]_EL1 */
+ orr x0, x0, #HDFGRTR_EL2_nBRBCTL_MASK
+ orr x2, x2, #HDFGWTR_EL2_nBRBCTL_MASK
+
+ /* Disable read traps for BRBIDR_EL1 */
+ orr x0, x0, #HDFGRTR_EL2_nBRBIDR_MASK
+
+.Lskip_brbe_reg_fgt_\@:
+#endif /* CONFIG_ARM64_BRBE */
msr_s SYS_HDFGRTR_EL2, x0
- msr_s SYS_HDFGWTR_EL2, x0
+ msr_s SYS_HDFGWTR_EL2, x2
mov x0, xzr
mrs x1, id_aa64pfr1_el1
@@ -194,7 +260,21 @@
.Lset_fgt_\@:
msr_s SYS_HFGRTR_EL2, x0
msr_s SYS_HFGWTR_EL2, x0
- msr_s SYS_HFGITR_EL2, xzr
+ mov x0, xzr
+#ifdef CONFIG_ARM64_BRBE
+ mrs x1, id_aa64dfr0_el1
+ ubfx x1, x1, #ID_AA64DFR0_EL1_BRBE_SHIFT, #4
+ cbz x1, .Lskip_brbe_insn_fgt_\@
+
+ /* Disable traps for BRBIALL instruction */
+ orr x0, x0, #HFGITR_EL2_nBRBIALL_MASK
+
+ /* Disable traps for BRBINJ instruction */
+ orr x0, x0, #HFGITR_EL2_nBRBINJ_MASK
+
+.Lskip_brbe_insn_fgt_\@:
+#endif /* CONFIG_ARM64_BRBE */
+ msr_s SYS_HFGITR_EL2, x0
mrs x1, id_aa64pfr0_el1 // AMU traps UNDEF without AMU
ubfx x1, x1, #ID_AA64PFR0_EL1_AMU_SHIFT, #4
@@ -229,6 +309,7 @@
__init_el2_nvhe_idregs
__init_el2_cptr
__init_el2_fgt
+ __init_el2_brbe
.endm
#ifndef __KVM_NVHE_HYPERVISOR__
--
2.25.1