From: Lorenzo Pieralisi <lpieralisi@kernel.org> To: Jason Gunthorpe <jgg@nvidia.com> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, ankita@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] KVM: arm64: allow the VM to select DEVICE_* and NORMAL_NC for IO memory Date: Mon, 13 Nov 2023 01:42:58 +0100 [thread overview] Message-ID: <ZVFxElNLcK46Vk9x@lpieralisi> (raw) In-Reply-To: <20231110142649.GO4488@nvidia.com> On Fri, Nov 10, 2023 at 10:26:49AM -0400, Jason Gunthorpe wrote: > On Thu, Nov 09, 2023 at 04:34:10PM +0100, Lorenzo Pieralisi wrote: > > > Relaxing S2 KVM device MMIO mappings to Normal-NC is not expected to > > trigger any issue on guest device reclaim use cases either (ie device > > MMIO unmap followed by a device reset) at least for PCIe devices, in that > > in PCIe a device reset is architected and carried out through PCI config > > space transactions that are naturally ordered wrt MMIO transactions > > according to the PCI ordering rules. > > This is not how I see that thread concluding.. > > The device reclaim problem belongs solely to VFIO, not KVM. VFIO must > ensure global ordering of access before the VMA is unmaped and access > after, that includes ordering whatever mechanism the VFIO driver uses > for reset. > > If there are quirky SOCs, or non-PCI devices that need something > stronger than the TLBI/etc sequence it should be fixed in VFIO (or > maybe even the arch code), not by blocking NORMAL_NC in the KVM. Such > a quirky SOC would broadly have security issues beyond KVM. https://lore.kernel.org/linux-arm-kernel/20231013092934.GA13524@willie-the-truck I think that Will's point _was_ related to the change we are making for KVM S2 mappings and related device transactions on device reclaim - ie reset, that's what I tried to convey (I probably simplified too much) that for PCI at least that should not trigger any regression/issue, in that BAR MMIO and reset transactions are decoupled streams and must follow the PCI ordering rules. Yes, it is VFIO responsibility but changing the S2 KVM mappings may have (for non-PCI devices) side effects compared to what we have today, I am not saying this should be a blocker I just summarized the thread above, the paragraph can be expanded. Lorenzo > > > It is worth noting that currently, to map devices MMIO space to user > > space in a device pass-through use case the VFIO framework applies memory > > attributes derived from pgprot_noncached() settings applied to VMAs, which > > Sometimes. VFIO uses a mix of pgprot_noncached and pgprot_device. AFAIK > we should change to to always use pgprot_device.. > > Thanks, > Jason
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From: Lorenzo Pieralisi <lpieralisi@kernel.org> To: Jason Gunthorpe <jgg@nvidia.com> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, ankita@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] KVM: arm64: allow the VM to select DEVICE_* and NORMAL_NC for IO memory Date: Mon, 13 Nov 2023 01:42:58 +0100 [thread overview] Message-ID: <ZVFxElNLcK46Vk9x@lpieralisi> (raw) In-Reply-To: <20231110142649.GO4488@nvidia.com> On Fri, Nov 10, 2023 at 10:26:49AM -0400, Jason Gunthorpe wrote: > On Thu, Nov 09, 2023 at 04:34:10PM +0100, Lorenzo Pieralisi wrote: > > > Relaxing S2 KVM device MMIO mappings to Normal-NC is not expected to > > trigger any issue on guest device reclaim use cases either (ie device > > MMIO unmap followed by a device reset) at least for PCIe devices, in that > > in PCIe a device reset is architected and carried out through PCI config > > space transactions that are naturally ordered wrt MMIO transactions > > according to the PCI ordering rules. > > This is not how I see that thread concluding.. > > The device reclaim problem belongs solely to VFIO, not KVM. VFIO must > ensure global ordering of access before the VMA is unmaped and access > after, that includes ordering whatever mechanism the VFIO driver uses > for reset. > > If there are quirky SOCs, or non-PCI devices that need something > stronger than the TLBI/etc sequence it should be fixed in VFIO (or > maybe even the arch code), not by blocking NORMAL_NC in the KVM. Such > a quirky SOC would broadly have security issues beyond KVM. https://lore.kernel.org/linux-arm-kernel/20231013092934.GA13524@willie-the-truck I think that Will's point _was_ related to the change we are making for KVM S2 mappings and related device transactions on device reclaim - ie reset, that's what I tried to convey (I probably simplified too much) that for PCI at least that should not trigger any regression/issue, in that BAR MMIO and reset transactions are decoupled streams and must follow the PCI ordering rules. Yes, it is VFIO responsibility but changing the S2 KVM mappings may have (for non-PCI devices) side effects compared to what we have today, I am not saying this should be a blocker I just summarized the thread above, the paragraph can be expanded. Lorenzo > > > It is worth noting that currently, to map devices MMIO space to user > > space in a device pass-through use case the VFIO framework applies memory > > attributes derived from pgprot_noncached() settings applied to VMAs, which > > Sometimes. VFIO uses a mix of pgprot_noncached and pgprot_device. AFAIK > we should change to to always use pgprot_device.. > > Thanks, > Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-11-13 0:43 UTC|newest] Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-09-07 18:14 [PATCH v1 0/2] KVM: arm64: support write combining and cachable IO memory in VMs ankita 2023-09-07 18:14 ` ankita 2023-09-07 18:14 ` [PATCH v1 1/2] KVM: arm64: determine memory type from VMA ankita 2023-09-07 18:14 ` ankita 2023-09-07 19:12 ` Jason Gunthorpe 2023-09-07 19:12 ` Jason Gunthorpe 2023-10-05 16:15 ` Catalin Marinas 2023-10-05 16:15 ` Catalin Marinas 2023-10-05 16:54 ` Jason Gunthorpe 2023-10-05 16:54 ` Jason Gunthorpe 2023-10-10 14:25 ` Catalin Marinas 2023-10-10 14:25 ` Catalin Marinas 2023-10-10 15:05 ` Jason Gunthorpe 2023-10-10 15:05 ` Jason Gunthorpe 2023-10-10 17:19 ` Catalin Marinas 2023-10-10 17:19 ` Catalin Marinas 2023-10-10 18:23 ` Jason Gunthorpe 2023-10-10 18:23 ` Jason Gunthorpe 2023-10-11 17:45 ` Catalin Marinas 2023-10-11 17:45 ` Catalin Marinas 2023-10-11 18:38 ` Jason Gunthorpe 2023-10-11 18:38 ` Jason Gunthorpe 2023-10-12 16:16 ` Catalin Marinas 2023-10-12 16:16 ` Catalin Marinas 2024-03-10 3:49 ` Ankit Agrawal 2024-03-10 3:49 ` Ankit Agrawal 2024-03-19 13:38 ` Jason Gunthorpe 2024-03-19 13:38 ` Jason Gunthorpe 2023-10-23 13:20 ` Shameerali Kolothum Thodi 2023-10-23 13:20 ` Shameerali Kolothum Thodi 2023-09-07 18:14 ` [PATCH v1 2/2] KVM: arm64: allow the VM to select DEVICE_* and NORMAL_NC for IO memory ankita 2023-09-07 18:14 ` ankita 2023-09-08 16:40 ` Catalin Marinas 2023-09-08 16:40 ` Catalin Marinas 2023-09-11 14:57 ` Lorenzo Pieralisi 2023-09-11 14:57 ` Lorenzo Pieralisi 2023-09-11 17:20 ` Jason Gunthorpe 2023-09-11 17:20 ` Jason Gunthorpe 2023-09-13 15:26 ` Lorenzo Pieralisi 2023-09-13 15:26 ` Lorenzo Pieralisi 2023-09-13 18:54 ` Jason Gunthorpe 2023-09-13 18:54 ` Jason Gunthorpe 2023-09-26 8:31 ` Lorenzo Pieralisi 2023-09-26 8:31 ` Lorenzo Pieralisi 2023-09-26 12:25 ` Jason Gunthorpe 2023-09-26 12:25 ` Jason Gunthorpe 2023-09-26 13:52 ` Catalin Marinas 2023-09-26 13:52 ` Catalin Marinas 2023-09-26 16:12 ` Lorenzo Pieralisi 2023-09-26 16:12 ` Lorenzo Pieralisi 2023-10-05 9:56 ` Lorenzo Pieralisi 2023-10-05 9:56 ` Lorenzo Pieralisi 2023-10-05 11:56 ` Jason Gunthorpe 2023-10-05 11:56 ` Jason Gunthorpe 2023-10-05 14:08 ` Lorenzo Pieralisi 2023-10-05 14:08 ` Lorenzo Pieralisi 2023-10-12 12:35 ` Will Deacon 2023-10-12 12:35 ` Will Deacon 2023-10-12 13:20 ` Jason Gunthorpe 2023-10-12 13:20 ` Jason Gunthorpe 2023-10-12 14:29 ` Lorenzo Pieralisi 2023-10-12 14:29 ` Lorenzo Pieralisi 2023-10-12 13:53 ` Catalin Marinas 2023-10-12 13:53 ` Catalin Marinas 2023-10-12 14:48 ` Will Deacon 2023-10-12 14:48 ` Will Deacon 2023-10-12 15:44 ` Jason Gunthorpe 2023-10-12 15:44 ` Jason Gunthorpe 2023-10-12 16:39 ` Will Deacon 2023-10-12 16:39 ` Will Deacon 2023-10-12 18:36 ` Jason Gunthorpe 2023-10-12 18:36 ` Jason Gunthorpe 2023-10-13 9:29 ` Will Deacon 2023-10-13 9:29 ` Will Deacon 2023-10-12 17:26 ` Catalin Marinas 2023-10-12 17:26 ` Catalin Marinas 2023-10-13 9:29 ` Will Deacon 2023-10-13 9:29 ` Will Deacon 2023-10-13 13:08 ` Catalin Marinas 2023-10-13 13:08 ` Catalin Marinas 2023-10-13 13:45 ` Jason Gunthorpe 2023-10-13 13:45 ` Jason Gunthorpe 2023-10-19 11:07 ` Catalin Marinas 2023-10-19 11:07 ` Catalin Marinas 2023-10-19 11:51 ` Jason Gunthorpe 2023-10-19 11:51 ` Jason Gunthorpe 2023-10-20 11:21 ` Catalin Marinas 2023-10-20 11:21 ` Catalin Marinas 2023-10-20 11:47 ` Jason Gunthorpe 2023-10-20 11:47 ` Jason Gunthorpe 2023-10-20 14:03 ` Lorenzo Pieralisi 2023-10-20 14:03 ` Lorenzo Pieralisi 2023-10-20 14:28 ` Jason Gunthorpe 2023-10-20 14:28 ` Jason Gunthorpe 2023-10-19 13:35 ` Lorenzo Pieralisi 2023-10-19 13:35 ` Lorenzo Pieralisi 2023-10-13 15:28 ` Lorenzo Pieralisi 2023-10-13 15:28 ` Lorenzo Pieralisi 2023-10-19 11:12 ` Catalin Marinas 2023-10-19 11:12 ` Catalin Marinas 2023-11-09 15:34 ` Lorenzo Pieralisi 2023-11-09 15:34 ` Lorenzo Pieralisi 2023-11-10 14:26 ` Jason Gunthorpe 2023-11-10 14:26 ` Jason Gunthorpe 2023-11-13 0:42 ` Lorenzo Pieralisi [this message] 2023-11-13 0:42 ` Lorenzo Pieralisi 2023-11-13 17:41 ` Catalin Marinas 2023-11-13 17:41 ` Catalin Marinas 2023-10-12 12:27 ` Will Deacon 2023-10-12 12:27 ` Will Deacon
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