From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C27EBC0650E for ; Wed, 3 Jul 2019 17:36:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9BA462189E for ; Wed, 3 Jul 2019 17:36:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727083AbfGCRgN (ORCPT ); Wed, 3 Jul 2019 13:36:13 -0400 Received: from foss.arm.com ([217.140.110.172]:53918 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726574AbfGCRgM (ORCPT ); Wed, 3 Jul 2019 13:36:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E3A06344; Wed, 3 Jul 2019 10:36:11 -0700 (PDT) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B89013F718; Wed, 3 Jul 2019 10:36:10 -0700 (PDT) Subject: Re: [RFC v2 14/14] kvm/arm: Align the VMID allocation with the arm64 ASID one To: Julien Grall Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com, julien.thierry@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will.deacon@arm.com References: <20190620130608.17230-1-julien.grall@arm.com> <20190620130608.17230-15-julien.grall@arm.com> From: James Morse Message-ID: <39d47f54-459f-ce07-91c0-0158896a6783@arm.com> Date: Wed, 3 Jul 2019 18:36:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190620130608.17230-15-julien.grall@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Julien, On 20/06/2019 14:06, Julien Grall wrote: > At the moment, the VMID algorithm will send an SGI to all the CPUs to > force an exit and then broadcast a full TLB flush and I-Cache > invalidation. > > This patch re-use the new ASID allocator. The > benefits are: > - CPUs are not forced to exit at roll-over. Instead the VMID will be > marked reserved and the context will be flushed at next exit. This > will reduce the IPIs traffic. > - Context invalidation is now per-CPU rather than broadcasted. + Catalin has a model of the asid-allocator. > With the new algo, the code is now adapted: > - The function __kvm_flush_vm_context() has been renamed to > __kvm_flush_cpu_vmid_context and now only flushing the current CPU context. > - The call to update_vttbr() will be done with preemption disabled > as the new algo requires to store information per-CPU. > - The TLBs associated to EL1 will be flushed when booting a CPU to > deal with stale information. This was previously done on the > allocation of the first VMID of a new generation. > > The measurement was made on a Seattle based SoC (8 CPUs), with the > number of VMID limited to 4-bit. The test involves running concurrently 40 > guests with 2 vCPUs. Each guest will then execute hackbench 5 times > before exiting. > diff --git a/arch/arm64/include/asm/kvm_asid.h b/arch/arm64/include/asm/kvm_asid.h > new file mode 100644 > index 000000000000..8b586e43c094 > --- /dev/null > +++ b/arch/arm64/include/asm/kvm_asid.h > @@ -0,0 +1,8 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ARM64_KVM_ASID_H__ > +#define __ARM64_KVM_ASID_H__ > + > +#include > + > +#endif /* __ARM64_KVM_ASID_H__ */ > + > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h > index ff73f5462aca..06821f548c0f 100644 > --- a/arch/arm64/include/asm/kvm_asm.h > +++ b/arch/arm64/include/asm/kvm_asm.h > @@ -62,7 +62,7 @@ extern char __kvm_hyp_init_end[]; > > extern char __kvm_hyp_vector[]; > > -extern void __kvm_flush_vm_context(void); > +extern void __kvm_flush_cpu_vmid_context(void); > extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa); As we've got a __kvm_tlb_flush_local_vmid(), would __kvm_tlb_flush_local_all() fit in better? (This mirrors local_flush_tlb_all() too) > extern void __kvm_tlb_flush_vmid(struct kvm *kvm); > extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu); > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 4bcd9c1291d5..7ef45b7da4eb 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -68,8 +68,8 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext); > void __extended_idmap_trampoline(phys_addr_t boot_pgd, phys_addr_t idmap_start); > > struct kvm_vmid { > - /* The VMID generation used for the virt. memory system */ > - u64 vmid_gen; > + /* The ASID used for the ASID allocator */ > + atomic64_t asid; Can we call this 'id' as happens in mm_context_t? (calling it asid is confusing) > u32 vmid; Can we filter out the generation bits in kvm_get_vttbr() in the same way the arch code does in cpu_do_switch_mm(). I think this saves writing back a cached pre-filtered version every time, or needing special hooks to know when the value changed. (so we can remove this variable) > }; > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > index bd5c55916d0d..e906278a67cd 100644 > --- a/virt/kvm/arm/arm.c > +++ b/virt/kvm/arm/arm.c > @@ -449,35 +447,17 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) (git made a mess of the diff here... squashed to just the new code:) > +static void vmid_update_ctxt(void *ctxt) > { > + struct kvm_vmid *vmid = ctxt; > + u64 asid = atomic64_read(&vmid->asid); > + vmid->vmid = asid & ((1ULL << kvm_get_vmid_bits()) - 1); I don't like having to poke this through the asid-allocator as a kvm-specific hack. Can we do it in kvm_get_vttbr()? > } > @@ -487,48 +467,11 @@ static bool need_new_vmid_gen(struct kvm_vmid *vmid) (git made a mess of the diff here... squashed to just the new code:) > static void update_vmid(struct kvm_vmid *vmid) > { > + int cpu = get_cpu(); > > + asid_check_context(&vmid_info, &vmid->asid, cpu, vmid); > > + put_cpu(); If we're calling update_vmid() in a pre-emptible context, aren't we already doomed? Could we use smp_processor_id() instead. > } > @@ -1322,6 +1271,8 @@ static void cpu_init_hyp_mode(void *dummy) > > __cpu_init_hyp_mode(pgd_ptr, hyp_stack_ptr, vector_ptr); > __cpu_init_stage2(); > + kvm_call_hyp(__kvm_flush_cpu_vmid_context); I think we only need to do this for VHE systems too. cpu_hyp_reinit() only does the call to cpu_init_hyp_mode() if !is_kernel_in_hyp_mode(). > } > > static void cpu_hyp_reset(void) > @@ -1429,6 +1380,17 @@ static inline void hyp_cpu_pm_exit(void) > > static int init_common_resources(void) > { > + /* > + * Initialize the ASID allocator telling it to allocate a single > + * VMID per VM. > + */ > + if (asid_allocator_init(&vmid_info, kvm_get_vmid_bits(), 1, > + vmid_flush_cpu_ctxt, vmid_update_ctxt)) > + panic("Failed to initialize VMID allocator\n"); Couldn't we return an error instead? The asid allocator is needed for user-space, its pointless to keep running if it fails. The same isn't true here. (and it would make it easier to debug what went wrong!) > + vmid_info.active = &active_vmids; > + vmid_info.reserved = &reserved_vmids; > + > kvm_set_ipa_limit(); Thanks, James