KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Gavin Shan <gshan@redhat.com>
To: Keqian Zhu <zhukeqian1@huawei.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v4 1/2] kvm/arm64: Remove the creation time's mapping of MMIO regions
Date: Fri, 23 Apr 2021 10:36:09 +1000
Message-ID: <b3da0d70-30e4-e128-cb76-16d335829541@redhat.com> (raw)
In-Reply-To: <20210415140328.24200-2-zhukeqian1@huawei.com>

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 <zhukeqian1@huawei.com>
> ---
>   arch/arm64/kvm/mmu.c | 38 +++-----------------------------------
>   1 file changed, 3 insertions(+), 35 deletions(-)
>

Reviewed-by: Gavin Shan <gshan@redhat.com>

  
> 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;
>   }
> 


  parent reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 14:03 [PATCH v4 0/2] kvm/arm64: Try stage2 block mapping for host device MMIO Keqian Zhu
2021-04-15 14:03 ` [PATCH v4 1/2] kvm/arm64: Remove the creation time's mapping of MMIO regions Keqian Zhu
2021-04-21  6:38   ` Gavin Shan
2021-04-21  6:28     ` Keqian Zhu
2021-04-22  2:12       ` Gavin Shan
2021-04-22  7:41         ` Keqian Zhu
2021-04-23  1:35           ` Gavin Shan
2021-04-23  1:36             ` Keqian Zhu
2021-04-23  0:36   ` Gavin Shan [this message]
2021-04-15 14:03 ` [PATCH v4 2/2] kvm/arm64: Try stage2 block mapping for host device MMIO Keqian Zhu
2021-04-15 14:08   ` Keqian Zhu
2021-04-16 14:44     ` Marc Zyngier
2021-04-17  1:05       ` Keqian Zhu
2021-04-21  7:52   ` Gavin Shan
2021-04-21  6:36     ` Keqian Zhu
2021-04-22  2:25       ` Gavin Shan
2021-04-22  6:51         ` Marc Zyngier
2021-04-23  0:42           ` Gavin Shan
2021-04-23  0:37   ` Gavin Shan

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=b3da0d70-30e4-e128-cb76-16d335829541@redhat.com \
    --to=gshan@redhat.com \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=maz@kernel.org \
    --cc=zhukeqian1@huawei.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git