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Subject: Re: [RFC KVM 02/27] KVM: x86: Introduce address_space_isolation
 module parameter
To:     Andy Lutomirski <luto@kernel.org>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Radim Krcmar <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        kvm list <kvm@vger.kernel.org>, X86 ML <x86@kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        jan.setjeeilers@oracle.com, Liran Alon <liran.alon@oracle.com>,
        Jonathan Adams <jwadams@google.com>
References: <1557758315-12667-1-git-send-email-alexandre.chartre@oracle.com>
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From:   Alexandre Chartre <alexandre.chartre@oracle.com>
Organization: Oracle Corporation
Message-ID: <1c541cde-a502-032a-244b-96e110507224@oracle.com>
Date:   Mon, 13 May 2019 17:55:44 +0200
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On 5/13/19 5:46 PM, Andy Lutomirski wrote:
> On Mon, May 13, 2019 at 7:39 AM Alexandre Chartre
> <alexandre.chartre@oracle.com> wrote:
>>
>> From: Liran Alon <liran.alon@oracle.com>
>>
>> Add the address_space_isolation parameter to the kvm module.
>>
>> When set to true, KVM #VMExit handlers run in isolated address space
>> which maps only KVM required code and per-VM information instead of
>> entire kernel address space.
> 
> Does the *entry* also get isolated?  If not, it seems less useful for
> side-channel mitigation.
> 

Yes, context is switched before VM entry. We switch back to kernel address
space if VM-exit handler needs it or when exiting the KVM_RUN ioctl.

alex.