linux-kernel - Re: [PATCH v2 0/6] Introduce KVM_{GET|SET}

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Date:   Sat, 29 May 2021 20:49:57 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Corbet <corbet@....net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v2 0/6] Introduce KVM_{GET|SET}_SREGS2 and fix PDPTR
 migration

On Wed, 2021-05-26 at 18:01 +0000, Sean Christopherson wrote:
> On Mon, Apr 26, 2021, 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 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 will be send soon as well.
> 
> How did you want to handle integration with the removal of
> pdptrs_changed()?
> 
> https://lkml.kernel.org/r/68ff1249-2902-43d5-3dfd-35b1f14c4f90@redhat.com
> 

Hi!
Sorry that I missed your mail. I will take a look in a day or so at
this, and I don't envision any significant trouble with removal of
pdptrs_changed, since it is only an optimization anyway.

Thanks,
	Best regards,
		Maxim Levitsky