From: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
To: <linux-arm-kernel@lists.infradead.org>,
<kvmarm@lists.cs.columbia.edu>, <linux-kernel@vger.kernel.org>
Cc: <maz@kernel.org>, <will@kernel.org>, <catalin.marinas@arm.com>,
<james.morse@arm.com>, <julien.thierry.kdev@gmail.com>,
<suzuki.poulose@arm.com>, <jean-philippe@linaro.org>,
<linuxarm@huawei.com>
Subject: [RFC PATCH 1/3] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available
Date: Thu, 6 May 2021 17:52:30 +0100 [thread overview]
Message-ID: <20210506165232.1969-2-shameerali.kolothum.thodi@huawei.com> (raw)
In-Reply-To: <20210506165232.1969-1-shameerali.kolothum.thodi@huawei.com>
From: Julien Grall <julien.grall@arm.com>
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@arm.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
---
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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next prev parent reply other threads:[~2021-05-06 16:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 16:52 [RFC PATCH 0/3] kvm/arm: New VMID allocator based on asid(2nd approach) Shameer Kolothum
2021-05-06 16:52 ` Shameer Kolothum [this message]
2021-05-06 16:52 ` [RFC PATCH 2/3] kvm/arm: Introduce a new vmid allocator for KVM Shameer Kolothum
2021-05-06 16:52 ` [RFC PATCH 3/3] kvm/arm: Align the VMID allocation with the arm64 ASID one Shameer Kolothum
2021-06-04 8:13 ` [RFC PATCH 0/3] kvm/arm: New VMID allocator based on asid(2nd approach) Shameerali Kolothum Thodi
2021-06-04 13:54 ` Marc Zyngier
2021-06-04 14:51 ` Shameerali Kolothum Thodi
2021-06-04 15:27 ` Marc Zyngier
2021-06-07 8:48 ` Jean-Philippe Brucker
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