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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>,
	<Alexandru.Elisei@arm.com>, <linuxarm@huawei.com>
Subject: [PATCH v2 1/3] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available
Date: Wed, 16 Jun 2021 16:56:04 +0100	[thread overview]
Message-ID: <20210616155606.2806-2-shameerali.kolothum.thodi@huawei.com> (raw)
In-Reply-To: <20210616155606.2806-1-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/kvm_mmu.h | 4 +---
 arch/arm64/kernel/cpufeature.c   | 9 +++++++++
 arch/arm64/tools/cpucaps         | 1 +
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 25ed956f9af1..2abdea7dcb43 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -223,9 +223,7 @@ 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 efed2830d141..0642ebe118b0 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2218,6 +2218,15 @@ 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,
+	},
 	{},
 };
 
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 21fbdda7086e..456b4cf1ba27 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -3,6 +3,7 @@
 # Internal CPU capabilities constants, keep this list sorted
 
 BTI
+HAS_16BIT_VMID
 HAS_32BIT_EL0
 HAS_32BIT_EL1
 HAS_ADDRESS_AUTH
-- 
2.17.1


  reply	other threads:[~2021-06-16 15:57 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 15:56 [PATCH v2 0/3] kvm/arm: New VMID allocator based on asid Shameer Kolothum
2021-06-16 15:56 ` Shameer Kolothum [this message]
2021-07-21 15:23   ` [PATCH v2 1/3] arch/arm64: Introduce a capability to tell whether 16-bit VMID is available Will Deacon
2021-07-22  6:24     ` Shameerali Kolothum Thodi
2021-06-16 15:56 ` [PATCH v2 2/3] kvm/arm: Introduce a new vmid allocator for KVM Shameer Kolothum
2021-07-21 16:06   ` Will Deacon
2021-07-22  6:34     ` Shameerali Kolothum Thodi
2021-06-16 15:56 ` [PATCH v2 3/3] kvm/arm: Align the VMID allocation with the arm64 ASID one Shameer Kolothum
2021-07-21 16:31   ` Will Deacon
2021-07-22  6:45     ` Shameerali Kolothum Thodi
2021-07-22  9:11       ` Quentin Perret
2021-07-22 19:33         ` Marco Elver
2021-07-22  9:50       ` Will Deacon
2021-07-22 15:22         ` Vladimir Murzin
2021-07-22 15:38           ` Will Deacon
2021-07-23 15:49             ` Vladimir Murzin
2021-07-13  7:07 ` [PATCH v2 0/3] kvm/arm: New VMID allocator based on asid Shameerali Kolothum Thodi

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