linux-kernel - Re: [PATCH] KVM: nVMX: pass valid guest linear-address to the L1

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Message-ID: <60fc4f75-7e46-fdb4-e790-f434d9aefbeb@redhat.com>
Date:   Mon, 5 Sep 2016 15:16:09 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jan Dakinevich <jan.dakinevich@...il.com>,
        Wanpeng Li <kernellwp@...il.com>
Cc:     kvm <kvm@...r.kernel.org>, Radim Krcmar <rkrcmar@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        ynorov@...iumnetworks.com
Subject: Re: [PATCH] KVM: nVMX: pass valid guest linear-address to the L1



On 05/09/2016 15:02, Jan Dakinevich wrote:
> > No, nested_ept_inject_page_fault() will set
> > vmcs12->guest_linear_address after L0 walks L1's EPT page table and
> > finds that the mapping is invalid if nested EPT is enabled.
>
> Acctually, nested_ept_inject_page_fault() doesn't do that, the routine
> sets only vmcs12->guest_physical_address, but
> vmcs12->guest_linear_address remains untouched. As result, after EPT
> fault from L2, vmcs_readl(GUEST_LINEAR_ADDRESS) in L1 always returns 0.
> 
> > prepare_vmcs12() just copies the vmcs field that could have changed by
> > the L2 guest or the exit-information etc instead of all fields since
> > other fields are modified by L1 with VMWRITE, which already writes to
> > vmcs12 directly.
> 
> Yes, and guest linear-address considered as a part of exit information,
> provided by hardware.

I agree.  The patch seems okay to me, but I'll leave a couple days more
to Wanpeng.

Paolo