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From:   Jeff Moyer <jmoyer@redhat.com>
To:     dan.j.williams@intel.com
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
        Borislav Petkov <bp@alien8.de>, <linux-edac@vger.kernel.org>,
        <x86@kernel.org>, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] x86/pat: pass correct address to sanitize_phys
References: <x49tuknmosl.fsf@segfault.boston.devel.redhat.com>
Date:   Mon, 09 Aug 2021 11:58:05 -0400
In-Reply-To: <x49tuknmosl.fsf@segfault.boston.devel.redhat.com> (Jeff Moyer's
        message of "Wed, 21 Jul 2021 15:48:10 -0400")
Message-ID: <x494kbyehki.fsf@segfault.boston.devel.redhat.com>
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Ping?  This patch fixes a real problem seen in the field.  Can I get
some review?

Thanks!
Jeff

Jeff Moyer <jmoyer@redhat.com> writes:

> memtype_reserve takes an address range of the form [start, end).  It
> then passes the start and end addresses to sanitize_phys, which is meant
> to operate on the inclusive addresses.  If end falls at the end of the
> physical address space, sanitize_phys will return 0.  This can result in
> drivers failing to load:
>
> [   10.000087] mpt3sas_cm0: unable to map adapter memory! or resource not found
> [   10.000334] mpt3sas_cm0: failure at drivers/scsi/mpt3sas/mpt3sas_scsih.c:10597/_scsih_probe()!
>
> Fix this by passing the inclusive end address to sanitize_phys.
>
> Fixes: 510ee090abc3 ("x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses")
> Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
> --
> It might be worth adding a comment, here.  If there are any suggestions
> on what a sane wording would be, I'm all ears.
>
> diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
> index 3112ca7786ed..482557905294 100644
> --- a/arch/x86/mm/pat/memtype.c
> +++ b/arch/x86/mm/pat/memtype.c
> @@ -583,7 +583,7 @@ int memtype_reserve(u64 start, u64 end, enum page_cache_mode req_type,
>  	int err = 0;
>  
>  	start = sanitize_phys(start);
> -	end = sanitize_phys(end);
> +	end = sanitize_phys(end - 1) + 1;
>  	if (start >= end) {
>  		WARN(1, "%s failed: [mem %#010Lx-%#010Lx], req %s\n", __func__,
>  				start, end - 1, cattr_name(req_type));