linux-kernel - Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn

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Date:	Mon, 4 Jul 2016 09:38:15 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:	Kirti Wankhede <kwankhede@...dia.com>, Neo Jia <cjia@...dia.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn_range-ed



On 04/07/2016 08:39, Xiao Guangrong wrote:
> Why the memory mapped by this mmap() is not a portion of MMIO from
> underlayer physical device? If it is a valid system memory, is this
> interface
> really needed to implemented in vfio? (you at least need to set VM_MIXEDMAP
> if it mixed system memory with MMIO)

The KVM code does not care if VM_MIXEDMAP is set or not, it works in
either case.

Paolo

> IIUC, the kernel assumes that VM_PFNMAP is a continuous memory, e.g, like
> current KVM and vaddr_get_pfn() in vfio, but it seems nvdia's patchset
> breaks this semantic as ops->validate_map_request() can adjust the physical
> address arbitrarily. (again, the name 'validate' should be changed to match
> the thing as it is really doing)
> 
> 
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