Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2] x86/boot/64/clang: Use fixup_pointer() to access
 '__supported_pte_mask'
To:     Alexander Potapenko <glider@google.com>, mingo@kernel.org,
        kirill.shutemov@linux.intel.com
References: <20180508162829.7729-1-glider@google.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org, mka@chromium.org,
        dvyukov@google.com, md@google.com
From:   Dave Hansen <dave.hansen@linux.intel.com>
Openpgp: preference=signencrypt
Message-ID: <a67943d1-f7e8-c465-ce8d-a9c9a0a6f653@linux.intel.com>
Date:   Tue, 8 May 2018 09:49:39 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.7.0
MIME-Version: 1.0
In-Reply-To: <20180508162829.7729-1-glider@google.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 05/08/2018 09:28 AM, Alexander Potapenko wrote:
> Clang builds with defconfig started crashing after commit fb43d6cb91ef
> ("x86/mm: Do not auto-massage page protections")
> This was caused by introducing a new global access in __startup_64().
> 
> Code in __startup_64() can be relocated during execution, but the compiler
> doesn't have to generate PC-relative relocations when accessing globals
> from that function. Clang actually does not generate them, which leads
> to boot-time crashes. To work around this problem, every global pointer
> must be adjusted using fixup_pointer().

Looks good to me.  Thanks for adding the comment, especially!

Reviewed-by: Dave Hansen <dave.hansen@intel.com>