From: Sukadev Bhattiprolu Subject: Re: [PATCH V2 0/6] Enable NX 842 compression engine on Power9 Date: Tue, 18 Jul 2017 11:06:00 -0700 Message-ID: <20170718180600.GB21838@us.ibm.com> References: <1500334999.995.6.camel@hbabu-laptop> <20170718161444.72252c9c@roar.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Haren Myneni , mikey@neuling.org, herbert@gondor.apana.org.au, linux-crypto@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, ddstreet@ieee.org To: Nicholas Piggin Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:58444 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751392AbdGRSGH (ORCPT ); Tue, 18 Jul 2017 14:06:07 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6II5Plk001803 for ; Tue, 18 Jul 2017 14:06:07 -0400 Received: from e36.co.us.ibm.com (e36.co.us.ibm.com [32.97.110.154]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bsdcfxs77-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 18 Jul 2017 14:06:06 -0400 Received: from localhost by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 18 Jul 2017 12:06:05 -0600 Content-Disposition: inline In-Reply-To: <20170718161444.72252c9c@roar.ozlabs.ibm.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: Nicholas Piggin [nicholas.piggin@gmail.com] wrote: > On Mon, 17 Jul 2017 16:43:19 -0700 > Haren Myneni wrote: > > > [PATCH V2 0/6] Enable NX 842 compression engine on Power9 > > This patchset depends on VAS kernel changes: > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-May/158178.html > > Just a question, we no longer invalidate the copy buffer on context > switch after this patch: > > 07d2a628bc ("powerpc/64s: Avoid cpabort in context switch when possible") > > If your vas address mappings are visible only to kernel, only used in > process / kthread context, and only used with kernel preemption disabled, > this is okay. Kernel preemption is not explicitly disabled in the NX driver I think and > > If userspace can possibly copy/paste to the mappings or if you need to > sleep or call this from interrupt context, we need to work out how to > invalidate the copy buffer. user space cannot copy/paste to the mappings yet (that mechanism is further out). NX driver calls: vas_copy(&crb, ...); vas_paste(addr, ...); but not from an interrupt context. Can/should we disable premption between the copy/paste and to avoid having to invalidate the copy buffer? Sukadev