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Date: Tue, 5 Dec 2023 18:40:42 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>, ankita@nvidia.com,
	Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
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	kvmarm@lists.linux.dev, kvm@vger.kernel.org, lpieralisi@kernel.org,
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Subject: Re: [PATCH v2 1/1] KVM: arm64: allow the VM to select DEVICE_* and
 NORMAL_NC for IO memory
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On Tue, Dec 05, 2023 at 05:50:27PM +0000, Marc Zyngier wrote:
> On Tue, 05 Dec 2023 17:33:01 +0000,
> Catalin Marinas <catalin.marinas@arm.com> wrote:
> > Ideally we should do this for vfio only but we don't have an easy
> > way to convey this to KVM.
> 
> But if we want to limit this to PCIe, we'll have to find out. The
> initial proposal (a long while ago) had a flag conveying some
> information, and I'd definitely feel more confident having something
> like that.

We can add a VM_PCI_IO in the high vma flags to be set by
vfio_pci_core_mmap(), though it limits it to 64-bit architectures. KVM
knows this is PCI and relaxes things a bit. It's not generic though if
we need this later for something else.

A question for Lorenzo: do these BARs appear in iomem_resource? We could
search that up instead of a flag, something like the page_is_ram()
helper.

-- 
Catalin