[PATCH] arm64: Add the arm64.nolse_atomics command line option

Maria Yu
2023-07-10T06:01:29Z

In order to be able to disable lse_atomic even if cpu
support it, most likely because of memory controller
cannot deal with the lse atomic instructions, use a
new idreg override to deal with it.

Signed-off-by: Maria Yu <quic_aiquny@quicinc.com>
---
Documentation/admin-guide/kernel-parameters.txt | 2 ++
arch/arm64/include/asm/cpufeature.h | 1 +
arch/arm64/kernel/cpufeature.c | 4 +++-
arch/arm64/kernel/idreg-override.c | 11 +++++++++++
4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 85fb0fa5d091..6ad754549f1d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -433,6 +433,8 @@
arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
Set instructions support

+ arm64.nolse_atomic [ARM64] Unconditionally disable LSE Atomic support
+
ataflop= [HW,M68k]

atarimouse= [HW,MOUSE] Atari Mouse
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 96e50227f940..9d56dea1fe62 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -916,6 +916,7 @@ extern struct arm64_ftr_override id_aa64pfr0_override;
extern struct arm64_ftr_override id_aa64pfr1_override;
extern struct arm64_ftr_override id_aa64zfr0_override;
extern struct arm64_ftr_override id_aa64smfr0_override;
+extern struct arm64_ftr_override id_aa64isar0_override;
extern struct arm64_ftr_override id_aa64isar1_override;
extern struct arm64_ftr_override id_aa64isar2_override;

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index f9d456fe132d..9bd766880807 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -669,6 +669,7 @@ struct arm64_ftr_override __ro_after_init id_aa64pfr0_override;
struct arm64_ftr_override __ro_after_init id_aa64pfr1_override;
struct arm64_ftr_override __ro_after_init id_aa64zfr0_override;
struct arm64_ftr_override __ro_after_init id_aa64smfr0_override;
+struct arm64_ftr_override __ro_after_init id_aa64isar0_override;
struct arm64_ftr_override __ro_after_init id_aa64isar1_override;
struct arm64_ftr_override __ro_after_init id_aa64isar2_override;

@@ -721,7 +722,8 @@ static const struct __ftr_reg_entry {
ARM64_FTR_REG(SYS_ID_AA64DFR1_EL1, ftr_raz),

/* Op1 = 0, CRn = 0, CRm = 6 */
- ARM64_FTR_REG(SYS_ID_AA64ISAR0_EL1, ftr_id_aa64isar0),
+ ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64ISAR0_EL1, ftr_id_aa64isar0,
+ &id_aa64isar0_override),
ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1,
&id_aa64isar1_override),
ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64ISAR2_EL1, ftr_id_aa64isar2,
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 2fe2491b692c..af41ab4f3d94 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -105,6 +105,15 @@ static const struct ftr_set_desc pfr1 __initconst = {
},
};

+static const struct ftr_set_desc isar0 __initconst = {
+ .name = "id_aa64isar0",
+ .override = &id_aa64isar0_override,
+ .fields = {
+ FIELD("atomic", ID_AA64ISAR0_EL1_ATOMIC_SHIFT, NULL),
+ {}
+ },
+};
+
static const struct ftr_set_desc isar1 __initconst = {
.name = "id_aa64isar1",
.override = &id_aa64isar1_override,
@@ -163,6 +172,7 @@ static const struct ftr_set_desc * const regs[] __initconst = {
&mmfr1,
&pfr0,
&pfr1,
+ &isar0,
&isar1,
&isar2,
&smfr0,
@@ -185,6 +195,7 @@ static const struct {
{ "arm64.nomops", "id_aa64isar2.mops=0" },
{ "arm64.nomte", "id_aa64pfr1.mte=0" },
{ "nokaslr", "arm64_sw.nokaslr=1" },
+ { "arm64.nolse_atomic", "id_aa64isar0.atomic=0" },
};

static int __init parse_nokaslr(char *unused)
--
2.17.1