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([2600:1010:b062:3446:55bd:a895:1fd7:cbdb]) by smtp.gmail.com with ESMTPSA id b21-v6sm20809474pfm.97.2018.09.07.15.48.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Sep 2018 15:48:19 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (1.0) Subject: Re: [RFC][PATCH 1/8] x86/mm: clarify hardware vs. software "error_code" From: Andy Lutomirski X-Mailer: iPhone Mail (15G77) In-Reply-To: <20180907194854.74729D71@viggo.jf.intel.com> Date: Fri, 7 Sep 2018 15:48:18 -0700 Cc: linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com, peterz@infradead.org, tglx@linutronix.de, x86@kernel.org, luto@kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <561334F6-9C13-424A-95ED-D377CE48DA46@amacapital.net> References: <20180907194852.3C351B82@viggo.jf.intel.com> <20180907194854.74729D71@viggo.jf.intel.com> To: Dave Hansen Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sep 7, 2018, at 12:48 PM, Dave Hansen wro= te: >=20 >=20 > From: Dave Hansen >=20 > We pass around a variable called "error_code" all around the page > fault code. Sounds simple enough, especially since "error_code" looks > like it exactly matches the values that the hardware gives us on the > stack to report the page fault error code (PFEC in SDM parlance). >=20 > But, that's not how it works. >=20 > For part of the page fault handler, "error_code" does exactly match > PFEC. But, during later parts, it diverges and starts to mean > something a bit different. >=20 > Give it two names for its two jobs. How hard would it be to just remove sw_error_code instead? It seems like it= adds little value and much confusion. I=E2=80=99m also unconvinced that the warning is terribly useful. We=E2=80=99= re going to oops when this happens anyway. I=E2=80=99ll rebase my diagnostic patch on top of this series after it settl= es.