From: Alex Williamson <alex.williamson@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"Wang, Zhenyu Z" <zhenyu.z.wang@intel.com>,
"Zhao, Yan Y" <yan.y.zhao@intel.com>
Subject: Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking
Date: Tue, 17 Dec 2019 09:18:37 -0700 [thread overview]
Message-ID: <20191217091837.744982d3@x1.home> (raw)
In-Reply-To: <AADFC41AFE54684AB9EE6CBC0274A5D19D645E55@SHSMSX104.ccr.corp.intel.com>
On Tue, 17 Dec 2019 02:28:33 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:
> > From: Paolo Bonzini
> > Sent: Monday, December 16, 2019 6:08 PM
> >
> > [Alex and Kevin: there are doubts below regarding dirty page tracking
> > from VFIO and mdev devices, which perhaps you can help with]
> >
> > On 15/12/19 18:21, Peter Xu wrote:
> > > init_rmode_tss
> > > vmx_set_tss_addr
> > > kvm_vm_ioctl_set_tss_addr [*]
> > > init_rmode_identity_map
> > > vmx_create_vcpu [*]
> >
> > These don't matter because their content is not visible to userspace
> > (the backing storage is mmap-ed by __x86_set_memory_region). In fact, d
> >
> > > vmx_write_pml_buffer
> > > kvm_arch_write_log_dirty [&]
> > > kvm_write_guest
> > > kvm_hv_setup_tsc_page
> > > kvm_guest_time_update [&]
> > > nested_flush_cached_shadow_vmcs12 [&]
> > > kvm_write_wall_clock [&]
> > > kvm_pv_clock_pairing [&]
> > > kvmgt_rw_gpa [?]
> >
> > This then expands (partially) to
> >
> > intel_gvt_hypervisor_write_gpa
> > emulate_csb_update
> > emulate_execlist_ctx_schedule_out
> > complete_execlist_workload
> > complete_current_workload
> > workload_thread
> > emulate_execlist_ctx_schedule_in
> > prepare_execlist_workload
> > prepare_workload
> > dispatch_workload
> > workload_thread
> >
> > So KVMGT is always writing to GPAs instead of IOVAs and basically
> > bypassing a guest IOMMU. So here it would be better if kvmgt was
> > changed not use kvm_write_guest (also because I'd probably have nacked
> > that if I had known :)).
>
> I agree.
>
> >
> > As far as I know, there is some work on live migration with both VFIO
> > and mdev, and that probably includes some dirty page tracking API.
> > kvmgt could switch to that API, or there could be VFIO APIs similar to
> > kvm_write_guest but taking IOVAs instead of GPAs. Advantage: this would
> > fix the GPA/IOVA confusion. Disadvantage: userspace would lose the
> > tracking of writes from mdev devices. Kevin, are these writes used in
> > any way? Do the calls to intel_gvt_hypervisor_write_gpa covers all
> > writes from kvmgt vGPUs, or can the hardware write to memory as well
> > (which would be my guess if I didn't know anything about kvmgt, which I
> > pretty much don't)?
>
> intel_gvt_hypervisor_write_gpa covers all writes due to software mediation.
>
> for hardware updates, it needs be mapped in IOMMU through vfio_pin_pages
> before any DMA happens. The ongoing dirty tracking effort in VFIO will take
> every pinned page through that API as dirtied.
>
> However, currently VFIO doesn't implement any vfio_read/write_guest
> interface yet. and it doesn't make sense to use vfio_pin_pages for software
> dirtied pages, as pin is unnecessary and heavy involving iommu invalidation.
>
> Alex, if you are OK we'll work on such interface and move kvmgt to use it.
> After it's accepted, we can also mark pages dirty through this new interface
> in Kirti's dirty page tracking series.
I'm not sure what you're asking for, is it an interface for the host
CPU to read/write the memory backing of a mapped IOVA range without
pinning pages? That seems like something like that would make sense for
an emulation model where a page does not need to be pinned for physical
DMA. If you're asking more for an interface that understands the
userspace driver is a VM (ie. implied using a _guest postfix on the
function name) and knows about GPA mappings beyond the windows directly
mapped for device access, I'd not look fondly on such a request.
Thanks,
Alex
next prev parent reply other threads:[~2019-12-17 16:18 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 21:34 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
2019-11-29 21:34 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
2019-12-03 19:01 ` Sean Christopherson
2019-12-04 9:42 ` Paolo Bonzini
2019-12-09 22:05 ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 02/15] KVM: Add kvm/vcpu argument to mark_dirty_page_in_slot Peter Xu
2019-12-02 19:32 ` Sean Christopherson
2019-12-02 20:49 ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 03/15] KVM: Add build-time error check on kvm_run size Peter Xu
2019-12-02 19:30 ` Sean Christopherson
2019-12-02 20:53 ` Peter Xu
2019-12-02 22:19 ` Sean Christopherson
2019-12-02 22:40 ` Peter Xu
2019-12-03 5:50 ` Sean Christopherson
2019-12-03 13:41 ` Paolo Bonzini
2019-12-03 17:04 ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking Peter Xu
2019-12-02 20:10 ` Sean Christopherson
2019-12-02 21:16 ` Peter Xu
2019-12-02 21:50 ` Sean Christopherson
2019-12-02 23:09 ` Peter Xu
2019-12-03 13:48 ` Paolo Bonzini
2019-12-03 18:46 ` Sean Christopherson
2019-12-04 10:05 ` Paolo Bonzini
2019-12-07 0:29 ` Sean Christopherson
2019-12-09 9:37 ` Paolo Bonzini
2019-12-09 21:54 ` Peter Xu
2019-12-10 10:07 ` Paolo Bonzini
2019-12-10 15:52 ` Peter Xu
2019-12-10 17:09 ` Paolo Bonzini
2019-12-15 17:21 ` Peter Xu
2019-12-16 10:08 ` Paolo Bonzini
2019-12-16 18:54 ` Peter Xu
2019-12-17 9:01 ` Paolo Bonzini
2019-12-17 16:24 ` Peter Xu
2019-12-17 16:28 ` Paolo Bonzini
2019-12-18 21:58 ` Peter Xu
2019-12-18 22:24 ` Sean Christopherson
2019-12-18 22:37 ` Paolo Bonzini
2019-12-18 22:49 ` Peter Xu
2019-12-17 2:28 ` Tian, Kevin
2019-12-17 16:18 ` Alex Williamson [this message]
2019-12-17 16:30 ` Paolo Bonzini
2019-12-18 0:29 ` Tian, Kevin
[not found] ` <AADFC41AFE54684AB9EE6CBC0274A5D19D645E5F@SHSMSX104.ccr.corp.intel.com>
2019-12-17 5:17 ` Tian, Kevin
2019-12-17 5:25 ` Yan Zhao
2019-12-17 16:24 ` Alex Williamson
2019-12-03 19:13 ` Sean Christopherson
2019-12-04 10:14 ` Paolo Bonzini
2019-12-04 14:33 ` Sean Christopherson
2019-12-04 10:38 ` Jason Wang
2019-12-04 11:04 ` Paolo Bonzini
2019-12-04 19:52 ` Peter Xu
2019-12-05 6:51 ` Jason Wang
2019-12-05 12:08 ` Peter Xu
2019-12-05 13:12 ` Jason Wang
2019-12-10 13:25 ` Michael S. Tsirkin
2019-12-10 13:31 ` Paolo Bonzini
2019-12-10 16:02 ` Peter Xu
2019-12-10 21:53 ` Michael S. Tsirkin
2019-12-11 9:05 ` Paolo Bonzini
2019-12-11 13:04 ` Michael S. Tsirkin
2019-12-11 14:54 ` Peter Xu
2019-12-10 21:48 ` Michael S. Tsirkin
2019-12-11 12:53 ` Michael S. Tsirkin
2019-12-11 14:14 ` Paolo Bonzini
2019-12-11 20:59 ` Peter Xu
2019-12-11 22:57 ` Michael S. Tsirkin
2019-12-12 0:08 ` Paolo Bonzini
2019-12-12 7:36 ` Michael S. Tsirkin
2019-12-12 8:12 ` Paolo Bonzini
2019-12-12 10:38 ` Michael S. Tsirkin
2019-12-15 17:33 ` Peter Xu
2019-12-16 9:47 ` Michael S. Tsirkin
2019-12-16 15:07 ` Peter Xu
2019-12-16 15:33 ` Michael S. Tsirkin
2019-12-16 15:47 ` Peter Xu
2019-12-11 17:24 ` Christophe de Dinechin
2019-12-13 20:23 ` Peter Xu
2019-12-14 7:57 ` Paolo Bonzini
2019-12-14 16:26 ` Peter Xu
2019-12-16 9:29 ` Paolo Bonzini
2019-12-16 15:26 ` Peter Xu
2019-12-16 15:31 ` Paolo Bonzini
2019-12-16 15:43 ` Peter Xu
2019-12-17 12:16 ` Christophe de Dinechin
2019-12-17 12:19 ` Paolo Bonzini
2019-12-17 15:38 ` Peter Xu
2019-12-17 16:31 ` Paolo Bonzini
2019-12-17 16:42 ` Peter Xu
2019-12-17 16:48 ` Paolo Bonzini
2019-12-17 19:41 ` Peter Xu
2019-12-18 0:33 ` Paolo Bonzini
2019-12-18 16:32 ` Peter Xu
2019-12-18 16:41 ` Paolo Bonzini
2019-12-20 18:19 ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 05/15] KVM: Make dirty ring exclusive to dirty bitmap log Peter Xu
2019-11-29 21:34 ` [PATCH RFC 06/15] KVM: Introduce dirty ring wait queue Peter Xu
2019-11-29 21:34 ` [PATCH RFC 07/15] KVM: X86: Implement ring-based dirty memory tracking Peter Xu
2019-11-29 21:34 ` [PATCH RFC 08/15] KVM: selftests: Always clear dirty bitmap after iteration Peter Xu
2019-11-29 21:34 ` [PATCH RFC 09/15] KVM: selftests: Sync uapi/linux/kvm.h to tools/ Peter Xu
2019-11-29 21:35 ` [PATCH RFC 10/15] KVM: selftests: Use a single binary for dirty/clear log test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 11/15] KVM: selftests: Introduce after_vcpu_run hook for dirty " Peter Xu
2019-11-29 21:35 ` [PATCH RFC 12/15] KVM: selftests: Add dirty ring buffer test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 13/15] KVM: selftests: Let dirty_log_test async for dirty ring test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 14/15] KVM: selftests: Add "-c" parameter to dirty log test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 15/15] KVM: selftests: Test dirty ring waitqueue Peter Xu
2019-11-30 8:29 ` [PATCH RFC 00/15] KVM: Dirty ring interface Paolo Bonzini
2019-12-02 2:13 ` Peter Xu
2019-12-03 13:59 ` Paolo Bonzini
2019-12-05 19:30 ` Peter Xu
2019-12-05 19:59 ` Paolo Bonzini
2019-12-05 20:52 ` Peter Xu
2019-12-02 20:21 ` Sean Christopherson
2019-12-02 20:43 ` Peter Xu
2019-12-04 10:39 ` Jason Wang
2019-12-04 19:33 ` Peter Xu
2019-12-05 6:49 ` Jason Wang
2019-12-11 13:41 ` Christophe de Dinechin
2019-12-11 14:16 ` Paolo Bonzini
2019-12-11 17:15 ` Peter Xu
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