[PATCH V2 6/7] arm64/boot: Enable EL2 requirements for FEAT_Debugv8p9

Anshuman Khandual
2024-10-28T05:50:14Z

Fine grained trap control for MDSELR_EL1 register needs to be configured in
HDFGRTR2_EL2, and HDFGWTR2_EL2 registers when kernel enters at EL1, but EL2
is also present. This adds a new helper __init_el2_fgt2() initializing this
new FEAT_FGT2 based fine grained registers.

MDCR_EL2.EBWE needs to be enabled for additional (beyond 16) breakpoint and
watchpoint exceptions when kernel enters at EL1, but EL2 is also present.
This updates __init_el2_debug() as required for FEAT_Debugv8p9.

While here, also update booting.rst with MDCR_EL3 and SCR_EL3 requirements.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@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
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V2:

- Orr MDCR_EL2_EBWE directly without an intermittent register

Documentation/arch/arm64/booting.rst | 19 +++++++++++++++++++
arch/arm64/include/asm/el2_setup.h | 26 ++++++++++++++++++++++++++
arch/arm64/include/asm/kvm_arm.h | 1 +
3 files changed, 46 insertions(+)

diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst
index b57776a68f15..e69d972018cf 100644
--- a/Documentation/arch/arm64/booting.rst
+++ b/Documentation/arch/arm64/booting.rst
@@ -285,6 +285,12 @@ 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 (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:
@@ -319,6 +325,19 @@ Before jumping into the kernel, the following conditions must be met:
- ZCR_EL2.LEN must be initialised to the same value for all CPUs the
kernel will execute on.

+ For CPUs with FEAT_Debugv8p9 extension present:
+
+ - If the kernel is entered at EL1 and EL2 is present:
+
+ - HDFGRTR2_EL2.nMDSELR_EL1 (bit 5) must be initialized to 0b1
+ - HDFGWTR2_EL2.nMDSELR_EL1 (bit 5) must be initialized to 0b1
+ - MDCR_EL2.EBWE (bit 43) must be initialized to 0b1
+
+ - If EL3 is present:
+
+ - MDCR_EL3.TDA (bit 9) must be initialized to 0b0
+ - MDCR_EL3.EBWE (bit 43) must be initialized to 0b1
+
For CPUs with the Scalable Matrix Extension (FEAT_SME):

- If EL3 is present:
diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index e0ffdf13a18b..289e9d8f8ee6 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -97,6 +97,13 @@
// to own it.

.Lskip_trace_\@:
+ mrs x1, id_aa64dfr0_el1
+ ubfx x1, x1, #ID_AA64DFR0_EL1_DebugVer_SHIFT, #4
+ cmp x1, #ID_AA64DFR0_EL1_DebugVer_V8P9
+ b.lt .Lskip_dbg_v8p9_\@
+
+ orr x2, x2, #MDCR_EL2_EBWE
+.Lskip_dbg_v8p9_\@:
msr mdcr_el2, x2 // Configure debug traps
.endm

@@ -215,6 +222,24 @@
.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_\@
+
+ mrs x1, id_aa64dfr0_el1
+ ubfx x1, x1, #ID_AA64DFR0_EL1_DebugVer_SHIFT, #4
+ cmp x1, #ID_AA64DFR0_EL1_DebugVer_V8P9
+ b.lt .Lskip_dbg_v8p9_\@
+
+ mov_q x0, HDFGWTR2_EL2_nMDSELR_EL1
+ msr_s SYS_HDFGWTR2_EL2, x0
+ msr_s SYS_HDFGRTR2_EL2, x0
+.Lskip_dbg_v8p9_\@:
+.Lskip_fgt2_\@:
+.endm
+
.macro __init_el2_nvhe_prepare_eret
mov x0, #INIT_PSTATE_EL1
msr spsr_el2, x0
@@ -240,6 +265,7 @@
__init_el2_nvhe_idregs
__init_el2_cptr
__init_el2_fgt
+ __init_el2_fgt2
.endm

#ifndef __KVM_NVHE_HYPERVISOR__
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 109a85ee6910..34936f550118 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -312,6 +312,7 @@
GENMASK(15, 0))

/* Hyp Debug Configuration Register bits */
+#define MDCR_EL2_EBWE (UL(1) << 43)
#define MDCR_EL2_E2TB_MASK (UL(0x3))
#define MDCR_EL2_E2TB_SHIFT (UL(24))
#define MDCR_EL2_HPMFZS (UL(1) << 36)
--
2.25.1