lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 10 Aug 2021 11:19:30 -0700
From:   Dave Hansen <>
To:     "Kirill A. Shutemov" <>
Cc:     "Kirill A. Shutemov" <>,
        Borislav Petkov <>,
        Andy Lutomirski <>,
        Sean Christopherson <>,
        Andrew Morton <>,
        Joerg Roedel <>,
        Andi Kleen <>,
        Kuppuswamy Sathyanarayanan 
        David Rientjes <>,
        Vlastimil Babka <>,
        Tom Lendacky <>,
        Thomas Gleixner <>,
        Peter Zijlstra <>,
        Paolo Bonzini <>,
        Ingo Molnar <>,
        Varad Gautam <>,
        Dario Faggioli <>,,,,
Subject: Re: [PATCH 0/5] x86: Impplement support for unaccepted memory

On 8/10/21 10:51 AM, Kirill A. Shutemov wrote:
> On Tue, Aug 10, 2021 at 10:36:21AM -0700, Dave Hansen wrote:
>>> The difference is going to be substantially lower once we get it optimized
>>> properly.
>> What does this mean?  Is this future work in the kernel or somewhere in
>> the TDX hardware/firmware which will speed things up?
> Kernel has to be changed to accept memory in 2M and 1G chunks where
> possible. The interface exists and described in spec, but not yet used in
> guest kernel.

>From a quick scan of the spec, I only see:

> 7.9.3. Page Acceptance by the Guest TD: TDG.MEM.PAGE.ACCEPT ... The guest
> TD can accept a dynamically added 4KB page using TDG.MEM.PAGE.ACCEPT
> with the page GPA as an input.
Is there some other 2M/1G page-acceptance call that I'm missing?

> It would cut hypercall overhead dramatically. It makes upfront memory
> accept more bearable and lowers latency of lazy memory accept. So I expect
> the gap being not 20x, but like 3-5x (which is still huge).

It would be nice to be able to judge the benefits of this series based
on the final form.  I guess we'll take what we can get, though.

Either way, I'd still like to see some *actual* numbers for at least one

	With this series applied, userspace starts to run at X seconds
	after kernel boot.  Without this series, userspace runs at Y

Powered by blists - more mailing lists