Re: [PATCH V3 05/16] arm64/cpufeature: Introduce ID_DFR1 CPU register

From: Suzuki K Poulose
Date: Sun May 03 2020 - 17:35:07 EST


On 05/02/2020 02:33 PM, Anshuman Khandual wrote:
This adds basic building blocks required for ID_DFR1 CPU register which
provides top level information about the debug system in AArch32 state.
This is added per ARM DDI 0487F.a specification.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Suggested-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
arch/arm64/include/asm/cpu.h | 1 +
arch/arm64/include/asm/sysreg.h | 3 +++
arch/arm64/kernel/cpufeature.c | 10 ++++++++++
arch/arm64/kernel/cpuinfo.c | 1 +
arch/arm64/kvm/sys_regs.c | 2 +-
5 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
index 464e828a994d..d9a78bdec409 100644
--- a/arch/arm64/include/asm/cpu.h
+++ b/arch/arm64/include/asm/cpu.h
@@ -33,6 +33,7 @@ struct cpuinfo_arm64 {
u64 reg_id_aa64zfr0;
u32 reg_id_dfr0;
+ u32 reg_id_dfr1;
u32 reg_id_isar0;
u32 reg_id_isar1;
u32 reg_id_isar2;
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index c977449e02db..2e1e922e1409 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -154,6 +154,7 @@
#define SYS_MVFR1_EL1 sys_reg(3, 0, 0, 3, 1)
#define SYS_MVFR2_EL1 sys_reg(3, 0, 0, 3, 2)
#define SYS_ID_PFR2_EL1 sys_reg(3, 0, 0, 3, 4)
+#define SYS_ID_DFR1_EL1 sys_reg(3, 0, 0, 3, 5)
#define SYS_ID_AA64PFR0_EL1 sys_reg(3, 0, 0, 4, 0)
#define SYS_ID_AA64PFR1_EL1 sys_reg(3, 0, 0, 4, 1)
@@ -763,6 +764,8 @@
#define ID_ISAR4_WITHSHIFTS_SHIFT 4
#define ID_ISAR4_UNPRIV_SHIFT 0
+#define ID_DFR1_MTPMU_SHIFT 0
+
#define ID_ISAR0_DIVIDE_SHIFT 24
#define ID_ISAR0_DEBUG_SHIFT 20
#define ID_ISAR0_COPROC_SHIFT 16
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index a8247bf92959..2ce952d9668d 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -451,6 +451,11 @@ static const struct arm64_ftr_bits ftr_id_dfr0[] = {
ARM64_FTR_END,
};
+static const struct arm64_ftr_bits ftr_id_dfr1[] = {
+ S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR1_MTPMU_SHIFT, 4, 0),


- ID_UNALLOCATED(3,5),
+ ID_SANITISED(ID_DFR1_EL1),
ID_UNALLOCATED(3,6),
ID_UNALLOCATED(3,7),

IIUC, we should not expose the MTPMU to the KVM guests. Either we could drop this entire patch, or we should emulate the MTPMU to 0 in KVM.

Suzuki