From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Thu, 08 May 2003 16:58:07 +0000 Subject: RE: [Linux-ia64] High fpu register corruption Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Thu, 8 May 2003 09:33:55 -0700, "Mallick, Asit K" said: Asit> Andreas, The high FP save and restore in the context switch Asit> makes the assumption that user will not be modifying the Asit> psr.mfh and it will be only updated by the hardware. Not a chance. We can't rely on the application doing the Right Thing. In fact, having an application clear psr.mfh makes tons of sense, when it knows it's done using mfh. Asit> Without this assumption we can not optimize the FP Asit> save/restore for SMP systems (this patch will not cover all Asit> cases). If application wants the current high fpu state to be Asit> preserved then it should will not be able to modify the Asit> psr.mfh. Asit> What kind of applications are trying to modify the mfh? OpenSSL does (really: some underlying crypto code). I think you're misunderstanding the problem though: the problem is that application A clears psr.mfh and application B gets its fph state corrupted. So, really, this is just a bug that needs fixing. It won't affect the rest of the lazy fph save/restore logic. --david