linux-kernel - Re: [PATCH v6 20/34] x86, mpparse: Use memremap to map the mpf and mpc data

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Date:   Wed, 14 Jun 2017 18:07:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     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, 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>,
        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>
Subject: Re: [PATCH v6 20/34] x86, mpparse: Use memremap to map the mpf and
 mpc data

On Wed, Jun 07, 2017 at 02:16:43PM -0500, Tom Lendacky wrote:
> The SMP MP-table is built by UEFI and placed in memory in a decrypted
> state. These tables are accessed using a mix of early_memremap(),
> early_memunmap(), phys_to_virt() and virt_to_phys(). Change all accesses
> to use early_memremap()/early_memunmap(). This allows for proper setting
> of the encryption mask so that the data can be successfully accessed when
> SME is active.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/kernel/mpparse.c |   98 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 70 insertions(+), 28 deletions(-)

...

> @@ -515,6 +516,12 @@ void __init default_get_smp_config(unsigned int early)
>  	if (acpi_lapic && acpi_ioapic)
>  		return;
>  
> +	mpf = early_memremap(mpf_base, sizeof(*mpf));
> +	if (!mpf) {
> +		pr_err("MPTABLE: mpf early_memremap() failed\n");

If you're going to introduce new prefixes then add:

#undef pr_fmt
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

at the beginning of the file so that they all say "mpparse:" instead.

And pls make that message more user-friendly: "Error mapping MP table"
or so.

-- 
Regards/Gruss,
    Boris.

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