All of lore.kernel.org
 help / color / mirror / Atom feed
From: Xiao Guangrong <guangrong.xiao@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	qemu-devel@nongnu.org, Xiao Guangrong <xiaoguangrong@tencent.com>
Subject: Re: [PATCH 0/7] KVM: MMU: fast write protect
Date: Thu, 4 May 2017 11:36:55 +0800	[thread overview]
Message-ID: <9af959d5-23c2-abd4-6100-577755239d2f@gmail.com> (raw)
In-Reply-To: <878cbc47-316c-d508-a5a3-22029dee2203@redhat.com>



On 05/03/2017 10:57 PM, Paolo Bonzini wrote:
> 
> 
> On 03/05/2017 16:50, Xiao Guangrong wrote:
>> Furthermore, userspace has no knowledge about if PML is enable (it
>> can be required from sysfs, but it is a good way in QEMU), so it is
>> difficult for the usespace to know when to use write-protect-all.
>> Maybe we can make KVM_CAP_X86_WRITE_PROTECT_ALL_MEM return false if
>> PML is enabled?
> 
> Yes, that's a good idea.  Though it's a pity that, with PML, setting the
> dirty bit will still do the massive walk of the rmap.  At least with
> reset_dirty_pages it's done a little bit at a time.
> 
>>> Also, I wonder how the alternative write protection mechanism would
>>> affect performance of the dirty page ring buffer patches.  You would do
>>> the write protection of all memory at the end of
>>> kvm_vm_ioctl_reset_dirty_pages.  You wouldn't even need a separate
>>> ioctl, which is nice.  On the other hand, checkpoints would be more
>>> frequent and most pages would be write-protected, so it would be more
>>> expensive to rebuild the shadow page tables...
>>
>> Yup, write-protect-all can improve reset_dirty_pages indeed, i will
>> apply your idea after reset_dirty_pages is merged.
>>
>> However, we still prefer to have a separate ioctl for write-protect-all
>> which cooperates with KVM_GET_DIRTY_LOG to improve live migration that
>> should not always depend on checkpoint.
> 
> Ok, I plan to merge the dirty ring pages early in 4.13 development.

Great.

As there is no conflict between these two patchsets except dirty
ring pages takes benefit from write-protect-all, i think they
can be developed and iterated independently, right?

Or you prefer to merge dirty ring pages first then review the
new version of this patchset later?

Thanks!

WARNING: multiple messages have this Message-ID
From: Xiao Guangrong <guangrong.xiao@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	qemu-devel@nongnu.org, Xiao Guangrong <xiaoguangrong@tencent.com>
Subject: Re: [Qemu-devel] [PATCH 0/7] KVM: MMU: fast write protect
Date: Thu, 4 May 2017 11:36:55 +0800	[thread overview]
Message-ID: <9af959d5-23c2-abd4-6100-577755239d2f@gmail.com> (raw)
In-Reply-To: <878cbc47-316c-d508-a5a3-22029dee2203@redhat.com>



On 05/03/2017 10:57 PM, Paolo Bonzini wrote:
> 
> 
> On 03/05/2017 16:50, Xiao Guangrong wrote:
>> Furthermore, userspace has no knowledge about if PML is enable (it
>> can be required from sysfs, but it is a good way in QEMU), so it is
>> difficult for the usespace to know when to use write-protect-all.
>> Maybe we can make KVM_CAP_X86_WRITE_PROTECT_ALL_MEM return false if
>> PML is enabled?
> 
> Yes, that's a good idea.  Though it's a pity that, with PML, setting the
> dirty bit will still do the massive walk of the rmap.  At least with
> reset_dirty_pages it's done a little bit at a time.
> 
>>> Also, I wonder how the alternative write protection mechanism would
>>> affect performance of the dirty page ring buffer patches.  You would do
>>> the write protection of all memory at the end of
>>> kvm_vm_ioctl_reset_dirty_pages.  You wouldn't even need a separate
>>> ioctl, which is nice.  On the other hand, checkpoints would be more
>>> frequent and most pages would be write-protected, so it would be more
>>> expensive to rebuild the shadow page tables...
>>
>> Yup, write-protect-all can improve reset_dirty_pages indeed, i will
>> apply your idea after reset_dirty_pages is merged.
>>
>> However, we still prefer to have a separate ioctl for write-protect-all
>> which cooperates with KVM_GET_DIRTY_LOG to improve live migration that
>> should not always depend on checkpoint.
> 
> Ok, I plan to merge the dirty ring pages early in 4.13 development.

Great.

As there is no conflict between these two patchsets except dirty
ring pages takes benefit from write-protect-all, i think they
can be developed and iterated independently, right?

Or you prefer to merge dirty ring pages first then review the
new version of this patchset later?

Thanks!

  reply	other threads:[~2017-05-04  3:37 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-03 10:52 guangrong.xiao
2017-05-03 10:52 ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 1/7] KVM: MMU: correct the behavior of mmu_spte_update_no_track guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 2/7] KVM: MMU: introduce possible_writable_spte_bitmap guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 3/7] KVM: MMU: introduce kvm_mmu_write_protect_all_pages guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 4/7] KVM: MMU: enable KVM_WRITE_PROTECT_ALL_MEM guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 5/7] KVM: MMU: allow dirty log without write protect guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 10:52 ` [PATCH 7/7] KVM: MMU: stop using mmu_spte_get_lockless under mmu-lock guangrong.xiao
2017-05-03 10:52   ` [Qemu-devel] " guangrong.xiao
2017-05-03 12:28 ` [PATCH 0/7] KVM: MMU: fast write protect Paolo Bonzini
2017-05-03 12:28   ` [Qemu-devel] " Paolo Bonzini
2017-05-03 14:50   ` Xiao Guangrong
2017-05-03 14:50     ` [Qemu-devel] " Xiao Guangrong
2017-05-03 14:57     ` Paolo Bonzini
2017-05-03 14:57       ` [Qemu-devel] " Paolo Bonzini
2017-05-04  3:36       ` Xiao Guangrong [this message]
2017-05-04  3:36         ` Xiao Guangrong
2017-05-04  7:06         ` Paolo Bonzini
2017-05-04  7:06           ` [Qemu-devel] " Paolo Bonzini
2017-05-23  2:23           ` Xiao Guangrong
2017-05-23  2:23             ` [Qemu-devel] " Xiao Guangrong
2017-05-29 16:48             ` Paolo Bonzini
2017-05-29 16:48               ` [Qemu-devel] " Paolo Bonzini
2017-06-09  3:19               ` Xiao Guangrong
2017-06-09  3:19                 ` [Qemu-devel] " Xiao Guangrong
2017-06-05  7:36 ` Jay Zhou
2017-06-05  7:36   ` Jay Zhou
2017-06-06  2:56   ` Xiao Guangrong

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=9af959d5-23c2-abd4-6100-577755239d2f@gmail.com \
    --to=guangrong.xiao@gmail.com \
    --cc=avi.kivity@gmail.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mtosatti@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=qemu-devel@nongnu.org \
    --cc=rkrcmar@redhat.com \
    --cc=xiaoguangrong@tencent.com \
    --subject='Re: [PATCH 0/7] KVM: MMU: fast write protect' \
    /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

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.