From: Jike Song <jike.song@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>,
gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
kai huang <kai.huang@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Kevin Tian <kevin.tian@intel.com>
Subject: Re: [PATCH v3 00/11] KVM: x86: track guest page access
Date: Tue, 23 Feb 2016 19:50:18 +0800 [thread overview]
Message-ID: <56CC477A.4040606@intel.com> (raw)
In-Reply-To: <1457505373.27893292.1456221705730.JavaMail.zimbra@redhat.com>
On 02/23/2016 06:01 PM, Paolo Bonzini wrote:
> ----- Original Message -----
>> From: "Jike Song" <jike.song@intel.com>
>> To: "Xiao Guangrong" <guangrong.xiao@linux.intel.com>
>> Cc: "Paolo Bonzini" <pbonzini@redhat.com>, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
>> linux-kernel@vger.kernel.org, "kai huang" <kai.huang@linux.intel.com>, "Andrea Arcangeli" <aarcange@redhat.com>,
>> "Kevin Tian" <kevin.tian@intel.com>
>> Sent: Tuesday, February 23, 2016 4:02:25 AM
>> Subject: Re: [PATCH v3 00/11] KVM: x86: track guest page access
>>
>> +Kevin
>>
>> On 02/22/2016 06:05 PM, Xiao Guangrong wrote:
>>>
>>> On 02/19/2016 08:00 PM, Paolo Bonzini wrote:
>>>>
>>>> I still have a doubt: how are you going to handle invalidation of GPU
>>>> shadow page tables if a device (emulated in QEMU or even vhost) does DMA
>>>> to the PPGTT?
>>>
>>> I think Jike is the better one to answer this question, Jike, could you
>>> please clarify it? :)
>>>
>>
>> Sure :)
>>
>> Actually in guest PPGTT is manipulated by CPU rather than GPU. The
>> PPGTT page table itself are plain memory, composed & modified by the
>> GPU driver, i.e. by CPU in Non-Root mode.
>>
>> Given that, we write-protected guest PPGTT, when VM writes PPGTT, EPT
>> violation rather than DMA fault happens.
>
I may still misunderstand you, so apologize in advance ..
> I am not talking of DMA faults; I am talking of a guest that reads
> from disk into the PPGTT.
into PPGTT the page table itself? as said by Kevin in another mail,
this is NOT SUPPORTED.
> This is emulated DMA, and your approach of
> tracking guest page access from KVM means that you are not handling
> this. Is this right?
Right, our tacking mechanism cares only CPU write, not Device write.
However, there is *NO* DMA emulation, just similar to passthrough.
The device(IGD) is only cable of r/w memory according the
shadowed PPGTT, which is managed by VGPU device-model, guaranteed
only memory that owned by this vgpu can be mapped.
All we need is to track CPU writes from guest.
> If so, what happens if the guest does this
> kind of operation (for example because it is not using the PPGTT
> anymore)? KVMGT should not be confused the next time it works on
> that PPGTT page.
As explained above, the device-model won't allow such things to happen.
>
> Paolo
>
--
Thanks,
Jike
prev parent reply other threads:[~2016-02-23 11:50 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-14 11:31 [PATCH v3 00/11] KVM: x86: track guest page access Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 01/11] KVM: MMU: rename has_wrprotected_page to mmu_gfn_lpage_is_disallowed Xiao Guangrong
2016-02-19 11:08 ` Paolo Bonzini
2016-02-14 11:31 ` [PATCH v3 02/11] KVM: MMU: introduce kvm_mmu_gfn_{allow,disallow}_lpage Xiao Guangrong
2016-02-19 11:09 ` Paolo Bonzini
2016-02-14 11:31 ` [PATCH v3 03/11] KVM: MMU: introduce kvm_mmu_slot_gfn_write_protect Xiao Guangrong
2016-02-19 11:18 ` Paolo Bonzini
2016-02-14 11:31 ` [PATCH v3 04/11] KVM: page track: add the framework of guest page tracking Xiao Guangrong
2016-02-19 11:24 ` Paolo Bonzini
2016-02-23 3:57 ` Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 05/11] KVM: page track: introduce kvm_page_track_{add,remove}_page Xiao Guangrong
2016-02-19 11:37 ` Paolo Bonzini
2016-02-23 4:18 ` Xiao Guangrong
2016-02-23 14:15 ` Paolo Bonzini
2016-02-19 11:37 ` Paolo Bonzini
2016-02-23 4:18 ` Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 06/11] KVM: MMU: let page fault handler be aware tracked page Xiao Guangrong
2016-02-19 11:45 ` Paolo Bonzini
2016-02-23 4:19 ` Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 07/11] KVM: page track: add notifier support Xiao Guangrong
2016-02-19 11:51 ` Paolo Bonzini
2016-02-23 4:34 ` Xiao Guangrong
2016-02-23 14:16 ` Paolo Bonzini
2016-02-14 11:31 ` [PATCH v3 08/11] KVM: MMU: use page track for non-leaf shadow pages Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 09/11] KVM: MMU: simplify mmu_need_write_protect Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 10/11] KVM: MMU: clear write-flooding on the fast path of tracked page Xiao Guangrong
2016-02-19 11:55 ` Paolo Bonzini
2016-02-23 4:36 ` Xiao Guangrong
2016-02-14 11:31 ` [PATCH v3 11/11] KVM: MMU: apply page track notifier Xiao Guangrong
2016-02-19 11:56 ` Paolo Bonzini
2016-02-23 4:40 ` Xiao Guangrong
2016-02-23 14:17 ` Paolo Bonzini
2016-02-19 12:00 ` [PATCH v3 00/11] KVM: x86: track guest page access Paolo Bonzini
2016-02-22 10:05 ` Xiao Guangrong
2016-02-23 3:02 ` Jike Song
2016-02-23 5:44 ` Tian, Kevin
2016-02-23 12:13 ` Paolo Bonzini
2016-02-23 10:01 ` Paolo Bonzini
2016-02-23 11:50 ` Jike Song [this message]
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