[PATCH v3 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line

Marc Zyngier
2021-01-11T13:40:26Z

As we want to be able to disable VHE at runtime, let's match
"id_aa64mmfr1.vh=" from the command line as an override.
This doesn't have much effect yet as our boot code doesn't look
at the cpufeature, but only at the HW registers.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/cpufeature.h | 3 +++
arch/arm64/kernel/cpufeature.c | 6 +++++-
arch/arm64/kernel/idreg-override.c | 12 ++++++++++++
3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index fe0130d6c0ff..80a5f423444e 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -814,6 +814,9 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
return 8;
}

+extern u64 id_aa64mmfr1_val;
+extern u64 id_aa64mmfr1_mask;
+
u32 get_kvm_ipa_limit(void);
void dump_cpu_features(void);

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 1cc93a2324dc..cc435b3dcd53 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -555,6 +555,9 @@ static const struct arm64_ftr_bits ftr_raz[] = {

#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL)

+u64 id_aa64mmfr1_val;
+u64 id_aa64mmfr1_mask;
+
static const struct __ftr_reg_entry {
u32 sys_id;
struct arm64_ftr_reg *reg;
@@ -602,7 +605,8 @@ static const struct __ftr_reg_entry {

/* Op1 = 0, CRn = 0, CRm = 7 */
ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
- ARM64_FTR_REG(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1),
+ ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1,
+ &id_aa64mmfr1_val, &id_aa64mmfr1_mask),
ARM64_FTR_REG(SYS_ID_AA64MMFR2_EL1, ftr_id_aa64mmfr2),

/* Op1 = 0, CRn = 1, CRm = 2 */
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 392f93b67103..75d9845f489b 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -10,6 +10,7 @@
#include <linux/libfdt.h>

#include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
#include <asm/setup.h>

struct reg_desc {
@@ -22,7 +23,18 @@ struct reg_desc {
} fields[];
};

+static const struct reg_desc mmfr1 __initdata = {
+ .name = "id_aa64mmfr1",
+ .val = &id_aa64mmfr1_val,
+ .mask = &id_aa64mmfr1_mask,
+ .fields = {
+ { "vh", ID_AA64MMFR1_VHE_SHIFT },
+ {}
+ },
+};
+
static const struct reg_desc * const regs[] __initdata = {
+ &mmfr1,
};

static int __init find_field(const char *cmdline, const struct reg_desc *reg,
--
2.29.2