linux-kernel - Re: AMD SME encrpytion and PCI BAR pages to user space

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Message-ID: <20201019172506.GV6219@nvidia.com>
Date:   Mon, 19 Oct 2020 14:25:06 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Tom Lendacky <thomas.lendacky@....com>
CC:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arch@...r.kernel.org>, <linux-mm@...ck.org>,
        <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "Andy Lutomirski" <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Paolo Bonzini" <pbonzini@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        "Dave Young" <dyoung@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: AMD SME encrpytion and PCI BAR pages to user space

On Mon, Oct 19, 2020 at 12:11:36PM -0500, Tom Lendacky wrote:

> > Hum, I assume it is broken also. Actually quite a swath of drivers
> > and devices will be broken under this :\
> 
> Not sure what you mean by the last statement - in general or when running
> under VFIO/DPDK? In general, traditional in kernel drivers work just fine
> under SME without any changes.

Split user/kernel drivers are common enough. Looks like maybe ~50
drivers in the kernel potentially are mmaping IO memory so would be
broken here.

Looking for pgprot_noncached() or pgprot_writecombine() around VMA
mappings is a pretty good clue it is working on IO memory.

I checked through the infiniband ones and they seem to be using
io_remap vs remap properly, but other places may need fixing.

Jason