From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xgllK3z3rzDq66 for ; Mon, 28 Aug 2017 18:47:41 +1000 (AEST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v7S8i7ID024738 for ; Mon, 28 Aug 2017 04:47:38 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0b-001b2d01.pphosted.com with ESMTP id 2cm9ubeuqx-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 28 Aug 2017 04:47:38 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 28 Aug 2017 09:47:37 +0100 From: Frederic Barrat To: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, andrew.donnellan@au1.ibm.com, clombard@linux.vnet.ibm.com, vaibhav@linux.vnet.ibm.com Cc: benh@kernel.crashing.org, alistair@popple.id.au Subject: [PATCH 1/2] cxl: Fix driver use count Date: Mon, 28 Aug 2017 10:47:30 +0200 Message-Id: <20170828084731.14773-1-fbarrat@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , cxl keeps a driver use count, which is used with the hash memory model on p8 to know when to upgrade local TLBIs to global and to trigger callbacks to manage the MMU for PSL8. If a process opens a context and closes without attaching or fails the attachment, the driver use count is never decremented. As a consequence, TLB invalidations remain global, even if there are no active cxl contexts. We should increment the driver use count when the process is attaching to the cxl adapter, and not on open. It's not needed before the adapter starts using the context and the use count is decremented on the detach path, so it makes more sense. It affects only the user api. The kernel api is already doing The Right Thing. Signed-off-by: Frederic Barrat Cc: stable@vger.kernel.org # v4.2+ Fixes: 7bb5d91a4dda ("cxl: Rework context lifetimes") --- drivers/misc/cxl/api.c | 4 ++++ drivers/misc/cxl/file.c | 8 +++++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c index 1a138c83f877..e0dfd1eadd70 100644 --- a/drivers/misc/cxl/api.c +++ b/drivers/misc/cxl/api.c @@ -336,6 +336,10 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed, mmput(ctx->mm); } + /* + * Increment driver use count. Enables global TLBIs for hash + * and callacks to handle the segment table + */ cxl_ctx_get(); if ((rc = cxl_ops->attach_process(ctx, kernel, wed, 0))) { diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c index 0761271d68c5..b76a491a485d 100644 --- a/drivers/misc/cxl/file.c +++ b/drivers/misc/cxl/file.c @@ -95,7 +95,6 @@ static int __afu_open(struct inode *inode, struct file *file, bool master) pr_devel("afu_open pe: %i\n", ctx->pe); file->private_data = ctx; - cxl_ctx_get(); /* indicate success */ rc = 0; @@ -225,6 +224,12 @@ static long afu_ioctl_start_work(struct cxl_context *ctx, if (ctx->mm) mmput(ctx->mm); + /* + * Increment driver use count. Enables global TLBIs for hash + * and callacks to handle the segment table + */ + cxl_ctx_get(); + trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr); if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor, @@ -233,6 +238,7 @@ static long afu_ioctl_start_work(struct cxl_context *ctx, cxl_adapter_context_put(ctx->afu->adapter); put_pid(ctx->pid); ctx->pid = NULL; + cxl_ctx_put(); cxl_context_mm_count_put(ctx); goto out; } -- 2.11.0