linux-kernel - Re: [PATCH v3 0/8] Introduce KVM_{GET|SET}

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Message-ID: <90393d4d-2057-b8d1-6867-275ba99efe3f@redhat.com>
Date:   Thu, 10 Jun 2021 17:06:12 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     open list <linux-kernel@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v3 0/8] Introduce KVM_{GET|SET}_SREGS2 and fix PDPTR
 migration

On 07/06/21 11:01, Maxim Levitsky wrote:
> This patch set aims to fix few flaws that were discovered
> in KVM_{GET|SET}_SREGS on x86:
> 
> * There is no support for reading/writing PDPTRs although
>    these are considered to be part of the guest state.
> 
> * There is useless interrupt bitmap which isn't needed
> 
> * No support for future extensions (via flags and such)
> 
> Also if the user doesn't use the new SREG2 api, the PDPTR
> load after migration is now done on KVM_REQ_GET_NESTED_STATE_PAGES
> to at least read them correctly in cases when guest memory
> map is not up to date when nested state is loaded.
> 
> This patch series was tested by doing nested migration test
> of 32 bit PAE L1 + 32 bit PAE L2 on AMD and Intel and by
> nested migration test of 64 bit L1 + 32 bit PAE L2 on AMD.
> The later test currently fails on Intel (regardless of my patches).
> 
> Changes from V2:
>    - I took in the patch series from Sean Christopherson that
>      removes the pdptrs_changed function and rebased my code
>      on top of it.
>    - I updated the SET_SREGS2 ioctl to load PDPTRS from memory
>      when user haven't given PDPTRS.
>    - Minor refactoring all over the place.
> 
> Changes from V1:
>    - move only PDPTRS load to KVM_REQ_GET_NESTED_STATE_PAGES on VMX
>    - rebase on top of kvm/queue
>    - improve the KVM_GET_SREGS2 to have flag for PDPTRS
>      and remove padding
> 
> Patches to qemu to enable this feature were sent as well.
> 
> Maxim Levitsky (5):
>    KVM: nSVM: refactor the CR3 reload on migration
>    KVM: nVMX: delay loading of PDPTRs to KVM_REQ_GET_NESTED_STATE_PAGES
>    KVM: x86: introduce kvm_register_clear_available
>    KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2
>    KVM: x86: avoid loading PDPTRs after migration when possible
> 
> Sean Christopherson (3):
>    KVM: nVMX: Drop obsolete (and pointless) pdptrs_changed() check
>    KVM: nSVM: Drop pointless pdptrs_changed() check on nested transition
>    KVM: x86: Always load PDPTRs on CR3 load for SVM w/o NPT and a PAE
>      guest
> 
>   Documentation/virt/kvm/api.rst  |  48 +++++++++
>   arch/x86/include/asm/kvm_host.h |   7 +-
>   arch/x86/include/uapi/asm/kvm.h |  13 +++
>   arch/x86/kvm/kvm_cache_regs.h   |  12 +++
>   arch/x86/kvm/svm/nested.c       |  39 +++++--
>   arch/x86/kvm/svm/svm.c          |   6 +-
>   arch/x86/kvm/vmx/nested.c       |  32 ++++--
>   arch/x86/kvm/x86.c              | 176 +++++++++++++++++++++-----------
>   include/uapi/linux/kvm.h        |   4 +
>   9 files changed, 253 insertions(+), 84 deletions(-)
> 

Queued, thanks.

Paolo