From: Paolo Bonzini <pbonzini@redhat.com>
To: Arthur Chunqi Li <yzt356@gmail.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: EPT page fault procedure
Date: Thu, 31 Oct 2013 11:54:21 +0100 [thread overview]
Message-ID: <527236DD.5000804@redhat.com> (raw)
In-Reply-To: <CABpY8MKRSX+RLmqNAAp8pDG6vEGHOwa0AmdH5DHf7gAdeN4nRQ@mail.gmail.com>
Il 31/10/2013 10:07, Arthur Chunqi Li ha scritto:
> Sorry to disturb you with so many trivial questions in KVM EPT memory
> management and thanks for your patience.
No problem, please remain onlist though. Adding back kvm@vger.kernel.org.
> I got confused in the EPT
> page fault processing function (tdp_page_fault). I think when Qemu
> registers the memory region for a VM, physical memory mapped to this
> PVA region isn't allocated indeed. So the page fault procedure of EPT
> violation which maps GFN to PFN should allocate the real physical
> memory and establish the real mapping from PVA to PFA in Qemu's page
Do you mean HVA to PFN? If so, you can look at function hva_to_pfn. :)
> table. What is the point in tdp_page_fault() handling such mapping
> from PVA to PFA?
The EPT page table entry is created in __direct_map using the pfn
returned by try_async_pf. try_async_pf itself gets the pfn from
gfn_to_pfn_async and gfn_to_pfn_prot. Both of them call __gfn_to_pfn
with different arguments. __gfn_to_pfn first goes from GFN to HVA using
the memslots (gfn_to_memslot and, in __gfn_to_pfn_memslot,
__gfn_to_hva_many), then it calls hva_to_pfn.
Ultimately, hva_to_pfn_fast and hva_to_pfn_slow is where KVM calls
functions from the kernel's get_user_page family.
Paolo
next parent reply other threads:[~2013-10-31 10:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CABpY8MKRSX+RLmqNAAp8pDG6vEGHOwa0AmdH5DHf7gAdeN4nRQ@mail.gmail.com>
2013-10-31 10:54 ` Paolo Bonzini [this message]
2013-11-04 1:05 ` EPT page fault procedure Arthur Chunqi Li
2013-11-04 12:20 ` Paolo Bonzini
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