linux-kernel - Re: [PATCH v6 10/34] x86, x86/mm, x86/xen, olpc: Use __va() against just the physical address in cr3

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Date:   Thu, 8 Jun 2017 17:17:29 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Tom Lendacky <thomas.lendacky@....com>, linux-arch@...r.kernel.org,
        linux-efi@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org
Cc:     Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel <xen-devel@...ts.xen.org>
Subject: Re: [PATCH v6 10/34] x86, x86/mm, x86/xen, olpc: Use __va() against
 just the physical address in cr3

On 06/08/2017 05:02 PM, Tom Lendacky wrote:
> On 6/8/2017 3:51 PM, Boris Ostrovsky wrote:
>>
>>>
>>>> What may be needed is making sure X86_FEATURE_SME is not set for PV
>>>> guests.
>>>
>>> And that may be something that Xen will need to control through either
>>> CPUID or MSR support for the PV guests.
>>
>>
>> Only on newer versions of Xen. On earlier versions (2-3 years old) leaf
>> 0x80000007 is passed to the guest unchanged. And so is MSR_K8_SYSCFG.
>
> The SME feature is in leaf 0x8000001f, is that leaf passed to the guest
> unchanged?

Oh, I misread the patch where X86_FEATURE_SME is defined. Then all
versions, including the current one, pass it unchanged.

All that's needed is setup_clear_cpu_cap(X86_FEATURE_SME) in
xen_init_capabilities().


-boris