From: "Liu, Yi L" <yi.l.liu@intel.com>
To: Peter Xu <peterx@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"mst@redhat.com" <mst@redhat.com>,
"david@gibson.dropbear.id.au" <david@gibson.dropbear.id.au>,
"Tian, Kevin" <kevin.tian@intel.com>,
"Tian, Jun J" <jun.j.tian@intel.com>,
"Sun, Yi Y" <yi.y.sun@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Wu, Hao" <hao.wu@intel.com>,
"jean-philippe@linaro.org" <jean-philippe@linaro.org>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Yi Sun <yi.y.sun@linux.intel.com>,
Richard Henderson <rth@twiddle.net>,
Eduardo Habkost <ehabkost@redhat.com>
Subject: RE: [PATCH v1 07/22] intel_iommu: add set/unset_iommu_context callback
Date: Wed, 25 Mar 2020 09:37:37 +0000 [thread overview]
Message-ID: <A2975661238FB949B60364EF0F2C25743A201DFC@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <20200324152416.GV127076@xz-x1>
> From: Peter Xu <peterx@redhat.com>
> Sent: Tuesday, March 24, 2020 11:24 PM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [PATCH v1 07/22] intel_iommu: add set/unset_iommu_context callback
>
> On Tue, Mar 24, 2020 at 11:15:24AM +0000, Liu, Yi L wrote:
>
> [...]
>
> > > > struct VTDIOTLBEntry {
> > > > @@ -271,6 +282,8 @@ struct IntelIOMMUState {
> > > > /*
> > > > * Protects IOMMU states in general. Currently it protects the
> > > > * per-IOMMU IOTLB cache, and context entry cache in VTDAddressSpace.
> > > > + * Protect the update/usage of HostIOMMUContext pointer cached in
> > > > + * VTDBus->dev_icx array as array elements may be updated by
> > > > + hotplug
> > >
> > > I think the context update does not need to be updated, because they
> > > should always be with the BQL, right?
> >
> > Hmmmm, maybe I used bad description. My purpose is to protect the
> > stored HostIOMMUContext pointer in vIOMMU. With
> > pci_device_set/unset_iommu_context,
> > vIOMMU have a copy of HostIOMMUContext. If VFIO container is released
> > (e.g. hotpulg out device), HostIOMMUContext will alos be released.
> > This will trigger the pci_device_unset_iommu_context() to clean the
> > copy. To avoid using a staled HostIOMMUContext in vIOMMU, vIOMMU
> > should have a lock to block the pci_device_unset_iommu_context()
> > calling until other threads finished their HostIOMMUContext usage. Do
> > you want a description update here or other preference?
>
> Yeah, but hot plug/unplug will still take the BQL?
>
> Ah btw I think it's also OK to take the lock if you want or not sure about whether
> we'll always take the BQL in these paths.
I guess better to have an internal sync to avoid reference stales HostIOMMUContext. :-)
> But if so, instead of adding another
> "Protect the ..." sentence to the comment, would you mind list out what the lock is
> protecting?
>
> /*
> * iommu_lock protects:
> * - per-IOMMU IOTLB caches
> * - context entry caches
> * - ...
> */
>
> Or anything better than that. Thanks,
It looks good to me. Let me update it in next version.
Regards,
Yi Liu
next prev parent reply other threads:[~2020-03-25 9:37 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-22 12:35 [PATCH v1 00/22] intel_iommu: expose Shared Virtual Addressing to VMs Liu Yi L
2020-03-22 12:35 ` [PATCH v1 01/22] scripts/update-linux-headers: Import iommu.h Liu Yi L
2020-03-22 12:35 ` [PATCH v1 02/22] header file update VFIO/IOMMU vSVA APIs Liu Yi L
2020-03-29 16:32 ` Auger Eric
2020-03-30 7:06 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 03/22] vfio: check VFIO_TYPE1_NESTING_IOMMU support Liu Yi L
2020-03-22 12:36 ` [PATCH v1 04/22] hw/iommu: introduce HostIOMMUContext Liu Yi L
2020-03-23 20:58 ` Peter Xu
2020-03-24 10:00 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 05/22] hw/pci: modify pci_setup_iommu() to set PCIIOMMUOps Liu Yi L
2020-03-22 12:36 ` [PATCH v1 06/22] hw/pci: introduce pci_device_set/unset_iommu_context() Liu Yi L
2020-03-23 21:15 ` Peter Xu
2020-03-24 10:02 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 07/22] intel_iommu: add set/unset_iommu_context callback Liu Yi L
2020-03-23 21:29 ` Peter Xu
2020-03-24 11:15 ` Liu, Yi L
2020-03-24 15:24 ` Peter Xu
2020-03-25 9:37 ` Liu, Yi L [this message]
2020-03-22 12:36 ` [PATCH v1 08/22] vfio: init HostIOMMUContext per-container Liu Yi L
[not found] ` <20200323213943.GR127076@xz-x1>
2020-03-24 13:03 ` Liu, Yi L
2020-03-24 14:45 ` Peter Xu
2020-03-25 9:30 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 09/22] vfio/common: check PASID alloc/free availability Liu Yi L
2020-03-23 22:06 ` Peter Xu
2020-03-24 11:18 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 10/22] intel_iommu: add virtual command capability support Liu Yi L
2020-03-22 12:36 ` [PATCH v1 11/22] intel_iommu: process PASID cache invalidation Liu Yi L
2020-03-22 12:36 ` [PATCH v1 12/22] intel_iommu: add PASID cache management infrastructure Liu Yi L
2020-03-24 17:32 ` Peter Xu
2020-03-25 12:20 ` Liu, Yi L
2020-03-25 14:52 ` Peter Xu
2020-03-26 6:15 ` Liu, Yi L
2020-03-26 13:57 ` Liu, Yi L
2020-03-26 15:53 ` Peter Xu
2020-03-27 1:33 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 13/22] vfio: add bind stage-1 page table support Liu Yi L
2020-03-24 17:41 ` Peter Xu
2020-03-25 9:49 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 14/22] intel_iommu: bind/unbind guest page table to host Liu Yi L
2020-03-24 17:46 ` Peter Xu
2020-03-25 12:42 ` Liu, Yi L
2020-03-25 14:56 ` Peter Xu
2020-03-26 3:04 ` Liu, Yi L
2020-03-25 12:47 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 15/22] intel_iommu: replay guest pasid bindings " Liu Yi L
2020-03-24 18:00 ` Peter Xu
2020-03-25 13:14 ` Liu, Yi L
2020-03-25 15:06 ` Peter Xu
2020-03-26 3:17 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 16/22] intel_iommu: replay pasid binds after context cache invalidation Liu Yi L
2020-03-24 18:07 ` Peter Xu
2020-03-25 13:18 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 17/22] intel_iommu: do not pass down pasid bind for PASID #0 Liu Yi L
2020-03-24 18:13 ` Peter Xu
2020-03-25 10:42 ` Liu, Yi L
2020-03-25 15:12 ` Peter Xu
2020-03-26 2:42 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 18/22] vfio: add support for flush iommu stage-1 cache Liu Yi L
2020-03-24 18:19 ` Peter Xu
2020-03-25 10:40 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 19/22] intel_iommu: process PASID-based iotlb invalidation Liu Yi L
2020-03-24 18:26 ` Peter Xu
2020-03-25 13:36 ` Liu, Yi L
2020-03-25 15:15 ` Peter Xu
2020-03-29 11:17 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 20/22] intel_iommu: propagate PASID-based iotlb invalidation to host Liu Yi L
2020-03-24 18:34 ` Peter Xu
2020-03-25 13:21 ` Liu, Yi L
2020-03-26 5:41 ` Liu, Yi L
2020-03-26 13:02 ` Peter Xu
2020-03-26 13:22 ` Peter Xu
2020-03-26 13:33 ` Liu, Yi L
2020-03-26 13:23 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 21/22] intel_iommu: process PASID-based Device-TLB invalidation Liu Yi L
2020-03-24 18:36 ` Peter Xu
2020-03-25 9:19 ` Liu, Yi L
2020-03-22 12:36 ` [PATCH v1 22/22] intel_iommu: modify x-scalable-mode to be string option Liu Yi L
2020-03-24 18:39 ` Peter Xu
2020-03-25 13:22 ` Liu, Yi L
2020-03-22 13:25 ` [PATCH v1 00/22] intel_iommu: expose Shared Virtual Addressing to VMs no-reply
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