All of lore.kernel.org
 help / color / mirror / Atom feed
From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>
Cc: Mohammed Gamal <mgamal@redhat.com>,
	kvm list <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR
Date: Fri, 10 Jul 2020 19:16:14 +0200	[thread overview]
Message-ID: <9e784c62-15ee-63b7-4942-474493bac536@redhat.com> (raw)
In-Reply-To: <CALMp9eQXHGnXo4ACX2-qYww4XdRODMn-O6CAvhupib67Li9S2w@mail.gmail.com>

On 10/07/20 19:13, Jim Mattson wrote:
> On Fri, Jul 10, 2020 at 10:06 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>> On 10/07/20 18:30, Jim Mattson wrote:
>>>>
>>>> This can be problem when having a mixed setup of machines with 5-level page
>>>> tables and machines with 4-level page tables, as live migration can change
>>>> MAXPHYADDR while the guest runs, which can theoretically introduce bugs.
>>>
>>> Huh? Changing MAXPHYADDR while the guest runs should be illegal. Or
>>> have I missed some peculiarity of LA57 that makes MAXPHYADDR a dynamic
>>> CPUID information field?
>>
>> Changing _host_ MAXPHYADDR while the guest runs, such as if you migrate
>> from a host-maxphyaddr==46 to a host-maxphyaddr==52 machine (while
>> keeping guest-maxphyaddr==46).
> 
> Ah, but what does that have to do with LA57?

Intel only has MAXPHYADDR > 46 on LA57 machines (because in general OSes
like to have a physical 1:1 map into the kernel part of the virtual
address space, so having a higher MAXPHYADDR would be of limited use
with 48-bit linear addresses).

In other words, while this issue has existed forever it could be ignored
until IceLake introduced MAXPHYADDR==52 machines.  I'll introduce
something like this in a commit message.

Paolo


  reply	other threads:[~2020-07-10 17:16 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10 15:48 [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 1/9] KVM: x86: Add helper functions for illegal GPA checking and page fault injection Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 2/9] KVM: x86: mmu: Move translate_gpa() to mmu.c Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 3/9] KVM: x86: mmu: Add guest physical address check in translate_gpa() Mohammed Gamal
2020-07-10 17:41   ` Paolo Bonzini
2020-07-10 15:48 ` [PATCH v3 4/9] KVM: x86: rename update_bp_intercept to update_exception_bitmap Mohammed Gamal
2020-07-10 16:15   ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 5/9] KVM: x86: update exception bitmap on CPUID changes Mohammed Gamal
2020-07-10 16:25   ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 6/9] KVM: VMX: introduce vmx_need_pf_intercept Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 7/9] KVM: VMX: Add guest physical address check in EPT violation and misconfig Mohammed Gamal
2020-07-13 18:32   ` Sean Christopherson
2020-07-15 23:00   ` Sean Christopherson
2020-08-17 17:22     ` Sean Christopherson
2020-08-17 18:01       ` Paolo Bonzini
2020-10-09 16:17   ` Jim Mattson
2020-10-14 23:44     ` Jim Mattson
2020-10-23  3:14       ` Sean Christopherson
2020-10-23  9:22         ` Paolo Bonzini
2020-10-23 16:59           ` Jim Mattson
2020-10-23 17:16             ` Paolo Bonzini
2020-10-23 17:23               ` Jim Mattson
2020-10-23 17:43                 ` Paolo Bonzini
2021-01-15 19:35                   ` Jim Mattson
2021-01-20 21:16                     ` Jim Mattson
2021-01-27 20:57                       ` Jim Mattson
2021-06-21 18:31                         ` Jim Mattson
2020-07-10 15:48 ` [PATCH v3 8/9] KVM: VMX: optimize #PF injection when MAXPHYADDR does not match Mohammed Gamal
2020-07-10 15:48 ` [PATCH v3 9/9] KVM: x86: SVM: VMX: Make GUEST_MAXPHYADDR < HOST_MAXPHYADDR support configurable Mohammed Gamal
2020-07-10 17:40   ` Paolo Bonzini
2020-07-10 16:30 ` [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR Jim Mattson
2020-07-10 17:06   ` Paolo Bonzini
2020-07-10 17:13     ` Jim Mattson
2020-07-10 17:16       ` Paolo Bonzini [this message]
2020-07-10 17:26         ` Sean Christopherson
2020-07-10 17:26         ` Jim Mattson
2020-07-10 17:40           ` Paolo Bonzini
2020-07-10 17:49 ` 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=9e784c62-15ee-63b7-4942-474493bac536@redhat.com \
    --to=pbonzini@redhat.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mgamal@redhat.com \
    --cc=sean.j.christopherson@intel.com \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.