arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9

FEAT_PMUv3p9 registers such as PMICNTR_EL0, PMICFILTR_EL0, and PMUACR_EL1
access from EL1 requires appropriate EL2 fine grained trap configuration
via FEAT_FGT2 based trap control registers HDFGRTR2_EL2 and HDFGWTR2_EL2.
Otherwise such register accesses will result in traps into EL2.

Add a new helper __init_el2_fgt2() which initializes FEAT_FGT2 based fine
grained trap control registers HDFGRTR2_EL2 and HDFGWTR2_EL2 (setting the
bits nPMICNTR_EL0, nPMICFILTR_EL0 and nPMUACR_EL1) to enable access into
PMICNTR_EL0, PMICFILTR_EL0, and PMUACR_EL1 registers.

Also update booting.rst with SCR_EL3.FGTEn2 requirement for all FEAT_FGT2
based registers to be accessible in EL2.

Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kvmarm@lists.linux.dev
Fixes: 0bbff9e ("perf/arm_pmuv3: Add PMUv3.9 per counter EL0 access control")
Fixes: d8226d8 ("perf: arm_pmuv3: Add support for Armv9.4 PMU instruction counter")
Tested-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20250227035119.2025171-1-anshuman.khandual@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Documentation/arch/arm64/booting.rst

@@ -288,6 +288,12 @@ Before jumping into the kernel, the following conditions must be met:
 
     - SCR_EL3.FGTEn (bit 27) must be initialised to 0b1.
 
+  For CPUs with the Fine Grained Traps 2 (FEAT_FGT2) extension present:
+
+  - If EL3 is present and the kernel is entered at EL2:
+
+    - SCR_EL3.FGTEn2 (bit 59) must be initialised to 0b1.
+
   For CPUs with support for HCRX_EL2 (FEAT_HCX) present:
 
   - If EL3 is present and the kernel is entered at EL2:
@@ -382,6 +388,22 @@ Before jumping into the kernel, the following conditions must be met:
 
     - SMCR_EL2.EZT0 (bit 30) must be initialised to 0b1.
 
+  For CPUs with the Performance Monitors Extension (FEAT_PMUv3p9):
+
+ - If EL3 is present:
+
+    - MDCR_EL3.EnPM2 (bit 7) must be initialised to 0b1.
+
+ - If the kernel is entered at EL1 and EL2 is present:
+
+    - HDFGRTR2_EL2.nPMICNTR_EL0 (bit 2) must be initialised to 0b1.
+    - HDFGRTR2_EL2.nPMICFILTR_EL0 (bit 3) must be initialised to 0b1.
+    - HDFGRTR2_EL2.nPMUACR_EL1 (bit 4) must be initialised to 0b1.
+
+    - HDFGWTR2_EL2.nPMICNTR_EL0 (bit 2) must be initialised to 0b1.
+    - HDFGWTR2_EL2.nPMICFILTR_EL0 (bit 3) must be initialised to 0b1.
+    - HDFGWTR2_EL2.nPMUACR_EL1 (bit 4) must be initialised to 0b1.
+
   For CPUs with Memory Copy and Memory Set instructions (FEAT_MOPS):
 
   - If the kernel is entered at EL1 and EL2 is present:

arch/arm64/include/asm/el2_setup.h

@@ -233,6 +233,30 @@
 .Lskip_fgt_\@:
 .endm
 
+.macro __init_el2_fgt2
+	mrs	x1, id_aa64mmfr0_el1
+	ubfx	x1, x1, #ID_AA64MMFR0_EL1_FGT_SHIFT, #4
+	cmp	x1, #ID_AA64MMFR0_EL1_FGT_FGT2
+	b.lt	.Lskip_fgt2_\@
+
+	mov	x0, xzr
+	mrs	x1, id_aa64dfr0_el1
+	ubfx	x1, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
+	cmp	x1, #ID_AA64DFR0_EL1_PMUVer_V3P9
+	b.lt	.Lskip_pmuv3p9_\@
+
+	orr	x0, x0, #HDFGRTR2_EL2_nPMICNTR_EL0
+	orr	x0, x0, #HDFGRTR2_EL2_nPMICFILTR_EL0
+	orr	x0, x0, #HDFGRTR2_EL2_nPMUACR_EL1
+.Lskip_pmuv3p9_\@:
+	msr_s   SYS_HDFGRTR2_EL2, x0
+	msr_s   SYS_HDFGWTR2_EL2, x0
+	msr_s   SYS_HFGRTR2_EL2, xzr
+	msr_s   SYS_HFGWTR2_EL2, xzr
+	msr_s   SYS_HFGITR2_EL2, xzr
+.Lskip_fgt2_\@:
+.endm
+
 .macro __init_el2_gcs
 	mrs_s	x1, SYS_ID_AA64PFR1_EL1
 	ubfx	x1, x1, #ID_AA64PFR1_EL1_GCS_SHIFT, #4
@@ -283,6 +307,7 @@
 	__init_el2_nvhe_idregs
 	__init_el2_cptr
 	__init_el2_fgt
+	__init_el2_fgt2
         __init_el2_gcs
 .endm