From: Julien Grall <julien.grall@xxxxxxx>
At the moment, the function kvm_get_vmid_bits() is looking up for the
sanitized value of ID_AA64MMFR1_EL1 and extract the information
regarding the number of VMID bits supported.
This is fine as the function is mainly used during VMID roll-over. New
use in a follow-up patch will require the function to be called a every
context switch so we want the function to be more efficient.
A new capability is introduced to tell whether 16-bit VMID is
available.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
---
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/include/asm/kvm_mmu.h | 4 +---
arch/arm64/kernel/cpufeature.c | 9 +++++++++
3 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index c40f2490cd7b..acb92da5c254 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -67,7 +67,8 @@
#define ARM64_HAS_LDAPR 59
#define ARM64_KVM_PROTECTED_MODE 60
#define ARM64_WORKAROUND_NVIDIA_CARMEL_CNP 61
+#define ARM64_HAS_16BIT_VMID 62
-#define ARM64_NCAPS 62
+#define ARM64_NCAPS 63
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 90873851f677..c3080966ef83 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -213,9 +213,7 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled);
static inline unsigned int kvm_get_vmid_bits(void)
{
- int reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
-
- return get_vmid_bits(reg);
+ return cpus_have_const_cap(ARM64_HAS_16BIT_VMID) ? 16 : 8;
}
/*
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e5281e1c8f1d..ff956fb2f712 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2203,6 +2203,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.matches = has_cpuid_feature,
.min_field_value = 1,
},
+ {
+ .capability = ARM64_HAS_16BIT_VMID,
+ .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+ .sys_reg = SYS_ID_AA64MMFR1_EL1,
+ .field_pos = ID_AA64MMFR1_VMIDBITS_SHIFT,
+ .sign = FTR_UNSIGNED,
+ .min_field_value = ID_AA64MMFR1_VMIDBITS_16,
+ .matches = has_cpuid_feature,
+ },
{},
};
--
2.17.1
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