linux-kernel - Re: [PATCH] xen/arm: do not setup the runstate info page if kpti is enabled

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Message-ID: <4aca4d30-f418-bfab-8a9c-74f349f4ca02@oracle.com>
Date:   Wed, 30 Sep 2020 10:13:39 -0400
From:   boris.ostrovsky@...cle.com
To:     Stefano Stabellini <sstabellini@...nel.org>,
        linux-kernel@...r.kernel.org
Cc:     Stefano Stabellini <stefano.stabellini@...inx.com>,
        Bertrand Marquis <Bertrand.Marquis@....com>, jgross@...e.com
Subject: Re: [PATCH] xen/arm: do not setup the runstate info page if kpti is
 enabled

On 9/24/20 7:49 PM, Stefano Stabellini wrote:

> From: Stefano Stabellini <stefano.stabellini@...inx.com>
>
> The VCPUOP_register_runstate_memory_area hypercall takes a virtual
> address of a buffer as a parameter. The semantics of the hypercall are
> such that the virtual address should always be valid.
>
> When KPTI is enabled and we are running userspace code, the virtual
> address is not valid, thus, Linux is violating the semantics of
> VCPUOP_register_runstate_memory_area.
>
> Do not call VCPUOP_register_runstate_memory_area when KPTI is enabled.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...inx.com>
> CC: Bertrand Marquis <Bertrand.Marquis@....com>
> CC: boris.ostrovsky@...cle.com
> CC: jgross@...e.com


Applied to for-linus-5.10



-boris