From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id 20AB5140080 for ; Wed, 14 May 2014 21:15:29 +1000 (EST) Message-ID: <53735044.5030008@redhat.com> Date: Wed, 14 May 2014 12:15:16 +0100 From: Pedro Alves MIME-Version: 1.0 To: Anshuman Khandual , Pedro Alves Subject: Re: [PATCH V2 2/3] powerpc, ptrace: Enable support for transactional memory register sets References: <1399276469-13541-1-git-send-email-khandual@linux.vnet.ibm.com> <1399276469-13541-3-git-send-email-khandual@linux.vnet.ibm.com> <537252C0.6090005@redhat.com> <53730326.6000400@linux.vnet.ibm.com> In-Reply-To: <53730326.6000400@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Cc: mikey@neuling.org, avagin@openvz.org, oleg@redhat.com, linux-kernel@vger.kernel.org, michael@ellerman.id.au, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/14/14 06:46, Anshuman Khandual wrote: > On 05/13/2014 10:43 PM, Pedro Alves wrote: >> On 05/05/14 08:54, Anshuman Khandual wrote: >>> This patch enables get and set of transactional memory related register >>> sets through PTRACE_GETREGSET/PTRACE_SETREGSET interface by implementing >>> four new powerpc specific register sets i.e REGSET_TM_SPR, REGSET_TM_CGPR, >>> REGSET_TM_CFPR, REGSET_CVMX support corresponding to these following new >>> ELF core note types added previously in this regard. >>> >>> (1) NT_PPC_TM_SPR >>> (2) NT_PPC_TM_CGPR >>> (3) NT_PPC_TM_CFPR >>> (4) NT_PPC_TM_CVMX >> >> Sorry that I couldn't tell this from the code, but, what does the >> kernel return when the ptracer requests these registers and the >> program is not in a transaction? Specifically I'm wondering whether >> this follows the same semantics as the s390 port. >> > > Right now, it still returns the saved state of the registers from thread > struct. I had assumed that the user must know the state of the transaction > before initiating the ptrace request. I guess its better to check for > the transaction status before processing the request. In case if TM is not > active on that thread, we should return -EINVAL. I think s390 returns ENODATA in that case. https://sourceware.org/ml/gdb-patches/2013-06/msg00273.html We'll want some way to tell whether the system actually supports this. That could be ENODATA vs something-else (EINVAL or perhaps better EIO for "request is invalid"). s390 actually screwed that, though it got away because there's a bit in HWCAP to signal transactions support. See: https://sourceware.org/ml/gdb-patches/2013-11/msg00080.html Are you adding something to HWCAP too? > > I am not familiar with the s390 side of code. But if we look at the > s390_tdb_get function it checks for (regs->int_code & 0x200) before > processing the request. Not sure what 0x200 signifies though. -- Pedro Alves