linux-kernel - Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions

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Date:   Thu, 14 Jan 2021 13:42:06 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Wei Huang <wei.huang2@....com>, Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Bandan Das <bsd@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>
Subject: Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered
 by VM instructions

On Tue, 2021-01-12 at 23:15 -0600, Wei Huang wrote:
> 
> On 1/12/21 12:58 PM, Andy Lutomirski wrote:
> > Andrew Cooper points out that there may be a nicer workaround.  Make
> > sure that the SMRAM and HT region (FFFD00000000 - FFFFFFFFFFFF) are
> > marked as reserved in the guest, too.
> 
> In theory this proposed solution can avoid intercepting #GP. But in 
> reality SMRAM regions can be different on different machines. So this 
> solution can break after VM migration.
> 
I should add to this, that on my 3970X,
I just noticed that the problematic SMRAM region moved on
its own (likely due to the fact that I moved some pcie cards around recently).

Best regards,
	Maxim Levitsky