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Received: from szxga04-in.huawei.com ([45.249.212.190]) by bombadil.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lehGr-006EVO-PX for linux-arm-kernel@lists.infradead.org; Thu, 06 May 2021 16:54:43 +0000 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FbfkT4f4Vz1BHvj; Fri, 7 May 2021 00:52:01 +0800 (CST) Received: from A2006125610.china.huawei.com (10.47.85.115) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Fri, 7 May 2021 00:54:27 +0800 From: Shameer Kolothum To: , , CC: , , , , , , , 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 Message-ID: <20210506165232.1969-2-shameerali.kolothum.thodi@huawei.com> X-Mailer: git-send-email 2.12.0.windows.1 In-Reply-To: <20210506165232.1969-1-shameerali.kolothum.thodi@huawei.com> References: <20210506165232.1969-1-shameerali.kolothum.thodi@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.47.85.115] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210506_095442_025779_3338AFFF X-CRM114-Status: GOOD ( 12.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Julien Grall 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 Signed-off-by: Shameer Kolothum --- 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, + }, {}, };