linux-kernel - Re: [PATCH] KVM: nVMX: Fix CR4 after VMLAUNCH/VMRESUME failure

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Message-ID: <CANRm+CyqV6s6etBAveNTG2WjfMZrfuuN+HpF9Ub1ex=JjyA1yw@mail.gmail.com>
Date:   Wed, 7 Feb 2018 16:31:08 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] KVM: nVMX: Fix CR4 after VMLAUNCH/VMRESUME failure

2018-02-07 0:58 GMT+08:00 Jim Mattson <jmattson@...gle.com>:
> On Mon, Feb 5, 2018 at 4:57 PM, Wanpeng Li <kernellwp@...il.com> wrote:
>
>> This is effective one, what I restore in this patch is
>> achitectural/guest visible.
>
> This patch doesn't "restore" the guest visible CR4 to its value at the
> time of VMLAUNCH/VMRESUME. It loads a new CR4 value from the vmcs12.
> That behavior is incorrect.

You have another pointing out about this.
https://lkml.org/lkml/2018/2/5/518 vmcs12->host_cr3/host_cr4 has the
up-to-date value when L1 is running, it is still up-to-date after
vmexit due to L1 executes VMLAUNCH/VMRESUME, I think the value stays
the same before L0 emulates the VMLAUNCH/VMRESUME, according to below
comments, why vmcs12->host_cr3/cr4 is not the value which we should
restore?

* After an early L2 VM-entry failure, we're now back
* in L1 which thinks it just finished a VMLAUNCH or
* VMRESUME instruction

Regards,
Wanpeng Li