From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF4EEC43387 for ; Thu, 20 Dec 2018 08:25:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCC442176F for ; Thu, 20 Dec 2018 08:25:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731102AbeLTIZC (ORCPT ); Thu, 20 Dec 2018 03:25:02 -0500 Received: from ozlabs.ru ([107.173.13.209]:54840 "EHLO ozlabs.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731085AbeLTIY7 (ORCPT ); Thu, 20 Dec 2018 03:24:59 -0500 Received: from fstn1-p1.ozlabs.ibm.com (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id B5A2DAE80381; Thu, 20 Dec 2018 03:24:54 -0500 (EST) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Cc: Alexey Kardashevskiy , David Gibson , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, Alistair Popple , Reza Arbab , Sam Bobroff , Piotr Jaroszynski , =?UTF-8?q?Leonardo=20Augusto=20Guimar=C3=A3es=20Garcia?= , Jose Ricardo Ziviani , Daniel Henrique Barboza , Alex Williamson , Paul Mackerras , linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH kernel v7 17/20] powerpc/powernv/npu: Fault user page into the hypervisor's pagetable Date: Thu, 20 Dec 2018 19:23:47 +1100 Message-Id: <20181220082350.58113-18-aik@ozlabs.ru> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181220082350.58113-1-aik@ozlabs.ru> References: <20181220082350.58113-1-aik@ozlabs.ru> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a page fault happens in a GPU, the GPU signals the OS and the GPU driver calls the fault handler which populated a page table; this allows the GPU to complete an ATS request. On the bare metal get_user_pages() is enough as it adds a pte to the kernel page table but under KVM the partition scope tree does not get updated so ATS will still fail. This reads a byte from an effective address which causes HV storage interrupt and KVM updates the partition scope tree. Signed-off-by: Alexey Kardashevskiy --- arch/powerpc/platforms/powernv/npu-dma.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c index c6163b9..12b8421 100644 --- a/arch/powerpc/platforms/powernv/npu-dma.c +++ b/arch/powerpc/platforms/powernv/npu-dma.c @@ -1133,6 +1133,8 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea, u64 rc = 0, result = 0; int i, is_write; struct page *page[1]; + const char __user *u; + char c; /* mmap_sem should be held so the struct_mm must be present */ struct mm_struct *mm = context->mm; @@ -1145,18 +1147,17 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea, is_write ? FOLL_WRITE : 0, page, NULL, NULL); - /* - * To support virtualised environments we will have to do an - * access to the page to ensure it gets faulted into the - * hypervisor. For the moment virtualisation is not supported in - * other areas so leave the access out. - */ if (rc != 1) { status[i] = rc; result = -EFAULT; continue; } + /* Make sure partition scoped tree gets a pte */ + u = page_address(page[0]); + if (__get_user(c, u)) + result = -EFAULT; + status[i] = 0; put_page(page[0]); } -- 2.17.1