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Wed, 21 Apr 2021 04:38:21 +0000 (UTC) Received: from [10.64.54.47] (vpn2-54-47.bne.redhat.com [10.64.54.47]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7433550A8D; Wed, 21 Apr 2021 04:38:19 +0000 (UTC) Subject: Re: [PATCH v4 1/2] kvm/arm64: Remove the creation time's mapping of MMIO regions To: Keqian Zhu , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, Marc Zyngier References: <20210415140328.24200-1-zhukeqian1@huawei.com> <20210415140328.24200-2-zhukeqian1@huawei.com> From: Gavin Shan Message-ID: Date: Wed, 21 Apr 2021 16:38:28 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20210415140328.24200-2-zhukeqian1@huawei.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210420_213835_154084_2263A753 X-CRM114-Status: GOOD ( 25.74 ) 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: , Reply-To: Gavin Shan Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Keqian, On 4/16/21 12:03 AM, Keqian Zhu wrote: > The MMIO regions may be unmapped for many reasons and can be remapped > by stage2 fault path. Map MMIO regions at creation time becomes a > minor optimization and makes these two mapping path hard to sync. > > Remove the mapping code while keep the useful sanity check. > > Signed-off-by: Keqian Zhu > --- > arch/arm64/kvm/mmu.c | 38 +++----------------------------------- > 1 file changed, 3 insertions(+), 35 deletions(-) > After removing the logic to create stage2 mapping for VM_PFNMAP region, I think the "do { } while" loop becomes unnecessary and can be dropped completely. It means the only sanity check is to see if the memory slot overflows IPA space or not. In that case, KVM_MR_FLAGS_ONLY can be ignored because the memory slot's base address and length aren't changed when we have KVM_MR_FLAGS_ONLY. It seems the patch isn't based on "next" branch because find_vma() was replaced by find_vma_intersection() by one of my patches :) Thanks, Gavin > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 8711894db8c2..c59af5ca01b0 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1301,7 +1301,6 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > { > hva_t hva = mem->userspace_addr; > hva_t reg_end = hva + mem->memory_size; > - bool writable = !(mem->flags & KVM_MEM_READONLY); > int ret = 0; > > if (change != KVM_MR_CREATE && change != KVM_MR_MOVE && > @@ -1318,8 +1317,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > mmap_read_lock(current->mm); > /* > * A memory region could potentially cover multiple VMAs, and any holes > - * between them, so iterate over all of them to find out if we can map > - * any of them right now. > + * between them, so iterate over all of them. > * > * +--------------------------------------------+ > * +---------------+----------------+ +----------------+ > @@ -1330,50 +1328,20 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > */ > do { > struct vm_area_struct *vma = find_vma(current->mm, hva); > - hva_t vm_start, vm_end; > > if (!vma || vma->vm_start >= reg_end) > break; > > - /* > - * Take the intersection of this VMA with the memory region > - */ > - vm_start = max(hva, vma->vm_start); > - vm_end = min(reg_end, vma->vm_end); > - > if (vma->vm_flags & VM_PFNMAP) { > - gpa_t gpa = mem->guest_phys_addr + > - (vm_start - mem->userspace_addr); > - phys_addr_t pa; > - > - pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT; > - pa += vm_start - vma->vm_start; > - > /* IO region dirty page logging not allowed */ > if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) { > ret = -EINVAL; > - goto out; > - } > - > - ret = kvm_phys_addr_ioremap(kvm, gpa, pa, > - vm_end - vm_start, > - writable); > - if (ret) > break; > + } > } > - hva = vm_end; > + hva = min(reg_end, vma->vm_end); > } while (hva < reg_end); > > - if (change == KVM_MR_FLAGS_ONLY) > - goto out; > - > - spin_lock(&kvm->mmu_lock); > - if (ret) > - unmap_stage2_range(&kvm->arch.mmu, mem->guest_phys_addr, mem->memory_size); > - else if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) > - stage2_flush_memslot(kvm, memslot); > - spin_unlock(&kvm->mmu_lock); > -out: > mmap_read_unlock(current->mm); > return ret; > } > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel