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To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Kai Huang <kai.huang@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        KVM list <kvm@vger.kernel.org>,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "Brown, Len" <len.brown@intel.com>,
        "Luck, Tony" <tony.luck@intel.com>,
        Rafael J Wysocki <rafael.j.wysocki@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andi Kleen <ak@linux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Isaku Yamahata <isaku.yamahata@intel.com>
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From:   Dave Hansen <dave.hansen@intel.com>
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On 4/29/22 14:20, Dan Williams wrote:
> Is there something already like this today for people that, for
> example, attempt to use PCI BAR mappings as memory? Or does KVM simply
> allow for garbage-in garbage-out?

I'm just guessing, but I _assume_ those garbage PCI BAR mappings are how
KVM does device passthrough.

I know that some KVM users even use mem= to chop down the kernel-owned
'struct page'-backed memory, then have a kind of /dev/mem driver to let
the memory get mapped back into userspace.  KVM is happy to pass through
those mappings.