From: David Hildenbrand <david@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Andy Lutomirski <luto@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm list <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
Joerg Roedel <jroedel@suse.de>, Andi Kleen <ak@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Varad Gautam <varad.gautam@suse.com>,
Dario Faggioli <dfaggioli@suse.com>,
the arch/x86 maintainers <x86@kernel.org>,
linux-mm@kvack.org, linux-coco@lists.linux.dev,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>
Subject: Re: [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory
Date: Tue, 31 Aug 2021 21:12:44 +0200 [thread overview]
Message-ID: <949e6d95-266d-0234-3b86-6bd3c5267333@redhat.com> (raw)
In-Reply-To: <YSlnJpWh8fdpddTA@google.com>
On 28.08.21 00:28, Sean Christopherson wrote:
> On Fri, Aug 27, 2021, Andy Lutomirski wrote:
>>
>> On Thu, Aug 26, 2021, at 2:26 PM, David Hildenbrand wrote:
>>> On 26.08.21 19:05, Andy Lutomirski wrote:
>>
>>>> Oof. That's quite a requirement. What's the point of the VMA once all
>>>> this is done?
>>>
>>> You can keep using things like mbind(), madvise(), ... and the GUP code
>>> with a special flag might mostly just do what you want. You won't have
>>> to reinvent too many wheels on the page fault logic side at least.
>
> Ya, Kirill's RFC more or less proved a special GUP flag would indeed Just Work.
> However, the KVM page fault side of things would require only a handful of small
> changes to send private memslots down a different path. Compared to the rest of
> the enabling, it's quite minor.
>
> The counter to that is other KVM architectures would need to learn how to use the
> new APIs, though I suspect that there will be a fair bit of arch enabling regardless
> of what route we take.
>
>> You can keep calling the functions. The implementations working is a
>> different story: you can't just unmap (pte_numa-style or otherwise) a private
>> guest page to quiesce it, move it with memcpy(), and then fault it back in.
>
> Ya, I brought this up in my earlier reply. Even the initial implementation (without
> real NUMA support) would likely be painful, e.g. the KVM TDX RFC/PoC adds dedicated
> logic in KVM to handle the case where NUMA balancing zaps a _pinned_ page and then
> KVM fault in the same pfn. It's not thaaat ugly, but it's arguably more invasive
> to KVM's page fault flows than a new fd-based private memslot scheme.
I might have a different mindset, but less code churn doesn't
necessarily translate to "better approach".
I'm certainly not pushing for what I proposed (it's a rough, broken
sketch). I'm much rather trying to come up with alternatives that try
solving the same issue, handling the identified requirements.
I have a gut feeling that the list of requirements might not be complete
yet. For example, I wonder if we have to protect against user space
replacing private pages by shared pages or punishing random holes into
the encrypted memory fd.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-08-31 19:12 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 0:52 [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory Sean Christopherson
2021-08-24 10:48 ` Yu Zhang
2021-08-26 0:35 ` Sean Christopherson
2021-08-26 13:23 ` Yu Zhang
2021-08-26 10:15 ` David Hildenbrand
2021-08-26 17:05 ` Andy Lutomirski
2021-08-26 21:26 ` David Hildenbrand
2021-08-27 18:24 ` Andy Lutomirski
2021-08-27 22:28 ` Sean Christopherson
2021-08-31 19:12 ` David Hildenbrand [this message]
2021-08-31 20:45 ` Sean Christopherson
2021-09-01 7:51 ` David Hildenbrand
2021-08-27 2:31 ` Yu Zhang
2021-08-31 19:08 ` David Hildenbrand
2021-08-31 20:01 ` Andi Kleen
2021-08-31 20:15 ` David Hildenbrand
2021-08-31 20:39 ` Andi Kleen
2021-09-01 3:34 ` Yu Zhang
2021-09-01 4:53 ` Andy Lutomirski
2021-09-01 7:12 ` Tian, Kevin
2021-09-01 10:24 ` Yu Zhang
2021-09-01 16:07 ` Andy Lutomirski
2021-09-01 16:27 ` David Hildenbrand
2021-09-02 8:34 ` Yu Zhang
2021-09-02 8:44 ` David Hildenbrand
2021-09-02 11:02 ` Yu Zhang
2021-09-02 8:19 ` Yu Zhang
2021-09-02 18:41 ` Andy Lutomirski
2021-09-07 1:33 ` Yan Zhao
2021-09-02 9:27 ` Joerg Roedel
2021-09-02 18:41 ` Andy Lutomirski
2021-09-02 18:57 ` Sean Christopherson
2021-09-02 19:07 ` Dave Hansen
2021-09-02 20:42 ` Andy Lutomirski
2021-08-27 22:18 ` Sean Christopherson
2021-08-31 19:07 ` David Hildenbrand
2021-08-31 21:54 ` Sean Christopherson
2021-09-01 8:09 ` David Hildenbrand
2021-09-01 15:54 ` Andy Lutomirski
2021-09-01 16:16 ` David Hildenbrand
2021-09-01 17:09 ` Andy Lutomirski
2021-09-01 16:18 ` James Bottomley
2021-09-01 16:22 ` David Hildenbrand
2021-09-01 16:31 ` James Bottomley
2021-09-01 16:37 ` David Hildenbrand
2021-09-01 16:45 ` James Bottomley
2021-09-01 17:08 ` David Hildenbrand
2021-09-01 17:50 ` Sean Christopherson
2021-09-01 17:53 ` David Hildenbrand
2021-09-01 17:08 ` Andy Lutomirski
2021-09-01 17:13 ` James Bottomley
2021-09-02 10:18 ` Joerg Roedel
2021-09-01 18:24 ` Andy Lutomirski
2021-09-01 19:26 ` Dave Hansen
2021-09-07 15:00 ` Tom Lendacky
2021-09-01 4:58 ` Andy Lutomirski
2021-09-01 7:49 ` David Hildenbrand
2021-09-02 18:47 ` Kirill A. Shutemov
2021-09-02 20:33 ` Sean Christopherson
2021-09-03 19:14 ` Kirill A. Shutemov
2021-09-03 19:15 ` Andy Lutomirski
2021-09-10 17:18 ` Kirill A. Shutemov
2021-09-15 19:58 ` Chao Peng
2021-09-15 13:51 ` David Hildenbrand
2021-09-15 14:29 ` Kirill A. Shutemov
2021-09-15 14:59 ` David Hildenbrand
2021-09-15 15:35 ` David Hildenbrand
2021-09-15 20:04 ` Kirill A. Shutemov
2021-09-15 14:11 ` Kirill A. Shutemov
2021-09-16 7:36 ` Chao Peng
2021-09-16 9:24 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=949e6d95-266d-0234-3b86-6bd3c5267333@redhat.com \
--to=david@redhat.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=bp@alien8.de \
--cc=dave.hansen@intel.com \
--cc=dfaggioli@suse.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=jroedel@suse.de \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=kvm@vger.kernel.org \
--cc=linux-coco@lists.linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=rientjes@google.com \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=varad.gautam@suse.com \
--cc=vbabka@suse.cz \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
--cc=yu.c.zhang@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).