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Date: Tue, 24 Mar 2015 16:42:18 -0700
From: Dave Hansen <dave.hansen@intel.com>
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To: Andy Lutomirski <luto@amacapital.net>
CC: Thomas Gleixner <tglx@linutronix.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        X86 ML <x86@kernel.org>, Dave Hansen <dave.hansen@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, Suresh Siddha <sbsiddha@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Fenghua Yu <fenghua.yu@intel.com>
Subject: Re: [PATCH 01/17] x86, fpu: wrap get_xsave_addr() to make it safer
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On 03/24/2015 03:28 PM, Andy Lutomirski wrote:
> Your function appears to be getting it for write (I assume that's what
> the unlazy_fpu is for), so I'd rather have it called
> tsk_get_xsave_field_for_write or something like that.

It should be entirely read-only.

For MPX (the only user of get_xsave_addr() iirc), we are only worried
about getting the status codes (and addresses) out of the bndstatus
register and making sure that the kernel-recorded bounds directory
address matches the bndcfgu (configuration) register.

We don't ever write to the registers.