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>
---
Changes in v3:
- Patch added
---
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 f19fe4b9acc4..af8ab758b252 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -52,7 +52,8 @@
#define ARM64_HAS_IRQ_PRIO_MASKING 42
#define ARM64_HAS_DCPODP 43
#define ARM64_WORKAROUND_1463225 44
+#define ARM64_HAS_16BIT_VMID 45
-#define ARM64_NCAPS 45
+#define ARM64_NCAPS 46
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index befe37d4bc0e..2ce8055a84b8 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -413,9 +413,7 @@ static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd,
static inline unsigned int kvm_get_vmid_bits(void)
{
- int reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
-
- return (cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR1_VMIDBITS_SHIFT) == 2) ? 16 : 8;
+ 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 f29f36a65175..b401e56af35a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1548,6 +1548,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 1,
},
#endif
+ {
+ .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,
+ },
{},
};
--
2.11.0
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
