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: Wed, 21 Apr 2021 16:38:28 +1000 [thread overview]
Message-ID: <ad39c796-2778-df26-b0c6-231e7626a747@redhat.com> (raw)
In-Reply-To: <20210415140328.24200-2-zhukeqian1@huawei.com>
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 <zhukeqian1@huawei.com>
> ---
> 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;
> }
>
next prev parent reply other threads:[~2021-04-21 4:43 UTC|newest]
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 [this message]
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
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=ad39c796-2778-df26-b0c6-231e7626a747@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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).