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From: Paolo Bonzini <pbonzini@redhat.com>
To: Jike Song <jike.song@intel.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 05:01:45 -0500 (EST)	[thread overview]
Message-ID: <1457505373.27893292.1456221705730.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <56CBCBC1.8050902@intel.com>



----- 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 am not talking of DMA faults; I am talking of a guest that reads
from disk into the PPGTT.  This is emulated DMA, and your approach of
tracking guest page access from KVM means that you are not handling
this.  Is this right?  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.

Paolo

  parent reply	other threads:[~2016-02-23 10:02 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 [this message]
2016-02-23 11:50         ` Jike Song

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