[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <3131CDA2-F6CF-43AC-A9FC-448DC6983596@gmail.com>
Date: Mon, 17 Jun 2019 11:50:34 -0700
From: Nadav Amit <nadav.amit@...il.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>,
Alexander Graf <graf@...zon.com>,
Thomas Gleixner <tglx@...utronix.de>,
Marius Hillenbrand <mhillenb@...zon.de>,
kvm list <kvm@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linux-MM <linux-mm@...ck.org>,
Alexander Graf <graf@...zon.de>,
David Woodhouse <dwmw@...zon.co.uk>,
the arch/x86 maintainers <x86@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC 00/10] Process-local memory allocations for hiding KVM
secrets
> On Jun 17, 2019, at 11:07 AM, Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 6/17/19 9:53 AM, Nadav Amit wrote:
>>>> For anyone following along at home, I'm going to go off into crazy
>>>> per-cpu-pgds speculation mode now... Feel free to stop reading now. :)
>>>>
>>>> But, I was thinking we could get away with not doing this on _every_
>>>> context switch at least. For instance, couldn't 'struct tlb_context'
>>>> have PGD pointer (or two with PTI) in addition to the TLB info? That
>>>> way we only do the copying when we change the context. Or does that tie
>>>> the implementation up too much with PCIDs?
>>> Hmm, that seems entirely reasonable. I think the nasty bit would be
>>> figuring out all the interactions with PV TLB flushing. PV TLB
>>> flushes already don't play so well with PCID tracking, and this will
>>> make it worse. We probably need to rewrite all that code regardless.
>> How is PCID (as you implemented) related to TLB flushing of kernel (not
>> user) PTEs? These kernel PTEs would be global, so they would be invalidated
>> from all the address-spaces using INVLPG, I presume. No?
>
> The idea is that you have a per-cpu address space. Certain kernel
> virtual addresses would map to different physical address based on where
> you are running. Each of the physical addresses would be "owned" by a
> single CPU and would, by convention, never use a PGD that mapped an
> address unless that CPU that "owned" it.
>
> In that case, you never really invalidate those addresses.
I understand, but as I see it, this is not related directly to PCIDs.
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
