From patchwork Thu Feb 15 15:01:30 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Cameron X-Patchwork-Id: 13558600 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2182213248D for ; Thu, 15 Feb 2024 15:01:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708009300; cv=none; b=ca9LGx1+X3Q00vp8azBvmtGE6uWDS7Ue4AUCVWqJSwTHBG9eGCgb5hNCVo2MBupS8b+NzUwD2/jRtXds2EHa8eyLTuY0EVQC8ntglVoKC9+eiEuCufGtZn3RLZ9vTtvZQ/1ql37MsGHos32osXfWCdXHBn2//0WWM+D/OF7bAOA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708009300; c=relaxed/simple; bh=ZIRMLZwTlad5bPv4WkD9VO6H+xn7YzrCiZf2us+WAfQ=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=lG6X4escNOPMwG9602MRN0xWy++UO/glu2U5kfXXjrIyYT2Ch8YgcXtDkGXjm0gHGcn9BdFU1JpzsuxCUokiFpjIkZp+mABloPbOaMsnkVjKoDniNPXncZOwSCVouMoxCZEJGr+O7pQFKdsuYvFSOxyzhZ2oYmz8uIz1BXa/9aM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.186.31]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4TbJ7t5NSHz6J9fm; Thu, 15 Feb 2024 22:57:30 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id 5E5D31416EA; Thu, 15 Feb 2024 23:01:33 +0800 (CST) Received: from SecurePC-101-06.china.huawei.com (10.122.247.231) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Thu, 15 Feb 2024 15:01:32 +0000 From: Jonathan Cameron To: , Peter Maydell , Gregory Price , =?utf-8?q?Alex_Benn=C3=A9e?= , Sajjan Rao , Dimitrios Palyvos , , Paolo Bonzini , Eduardo Habkost CC: Subject: [PATCH 0/3 qemu] tcg/i386: Page tables in MMIO memory fixes (CXL) Date: Thu, 15 Feb 2024 15:01:30 +0000 Message-ID: <20240215150133.2088-1-Jonathan.Cameron@huawei.com> X-Mailer: git-send-email 2.39.2 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: lhrpeml500005.china.huawei.com (7.191.163.240) To lhrpeml500005.china.huawei.com (7.191.163.240) CXL memory is interleaved at granularities as fine as 64 bytes. To emulate this each read and write access undergoes address translation similar to that used in physical hardware. This is done using cfmws_ops for a memory region per CXL Fixed Memory Window (the PA address range in the host that is interleaved across host bridges and beyond. The OS programs interleaved decoders in the CXL Root Bridges, switch upstream ports and the corresponding decoders CXL type 3 devices who have to know the Host PA to Device PA mappings). Unfortunately this CXL memory may be used as normal memory and anything that can end up in RAM can be placed within it. As Linux has become more capable of handling this memory we've started to get quite a few bug reports for the QEMU support. However terrible the performance is people seem to like running actual software stacks on it :( This doesn't work for KVM - so for now CXL emulation remains TCG only. (unless you are very careful on how it is used!) I plan to add some safety guards at a later date to make it slightly harder for people to shoot themselves in the foot + a more limited set of CXL functionality that is safe (no interleaving!) Previously we had some issues with TCG reading instructions from CXL memory but that is now all working. This time the issues are around the Page Tables being in the CXL memory + DMA buffers being placed in it. The test setup I've been using is simple 2 way interleave via 2 root ports below a single CXL root complex. After configuration in Linux these are mapped to their own Numa Node and numactl --membind=1 ls followed by powering down the machine is sufficient to hit all the bugs addressed in this series. Thanks to Gregory, Peter and Alex for their help figuring this lot out. Note that I've included one patch from Peter without a SoB because so far it has only be posted in the discussion thread. Whilst thread started back at: https://lore.kernel.org/all/CAAg4PaqsGZvkDk_=PH+Oz-yeEUVcVsrumncAgegRKuxe_YoFhA@mail.gmail.com/ The QEMU part is from. https://lore.kernel.org/all/20240201130438.00001384@Huawei.com/ arm64 equivalent to follow. Gregory Price (1): target/i386: Enable page walking from MMIO memory Jonathan Cameron (1): tcg: Avoid double lock if page tables happen to be in mmio memory. Peter Maydell (1): accel/tcg: Set can_do_io at at start of lookup_tb_ptr helper accel/tcg/cpu-exec.c | 8 ++++ accel/tcg/cputlb.c | 9 ++++- target/i386/tcg/sysemu/excp_helper.c | 57 +++++++++++++++------------- 3 files changed, 45 insertions(+), 29 deletions(-)