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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3B7DC433FE for ; Mon, 17 Oct 2022 09:48:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231391AbiJQJs3 (ORCPT ); Mon, 17 Oct 2022 05:48:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230010AbiJQJsR (ORCPT ); Mon, 17 Oct 2022 05:48:17 -0400 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E36E5E30C for ; Mon, 17 Oct 2022 02:48:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1666000086; x=1697536086; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=8avkb8niqXxOei1jYk0QQPKLA+dnwojk9iKaLNjUT+Y=; b=Y/7k6SqYYPvxIoCbM6Oy51dsVYAEJdbKX/5PCJKBhCAiOA3KnAGDv3G9 DVG6p20M+aNMGYf5rSsze98c94iV9ICeelKtwzfBGXZ4H0ChdpGIqi6JA OHiEV1CoqBwwS2KuMMJhKLA7nCaRQIiKOxCMw6AV38QyWZpkgYWraGAqx 5h/WwVmj5cfAaGz1prNpPaOTAkhgUh86Yh+GDLF7k5pg7Ib1ihcSoaI8C PWwuHSMXZtWUbRodshMR6PN27PwtXnyM0cJl1FN8wFOl1rdsQ6eo/9h02 kWuVtiMhYNVuvgiPTbpvW3urSk6x2tApnJEjt7i4Dgs/Nmwk4wa9rcONc Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="332286070" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="332286070" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Oct 2022 02:48:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10502"; a="753576169" X-IronPort-AV: E=Sophos;i="5.95,191,1661842800"; d="scan'208";a="753576169" Received: from liuzhao-optiplex-7080.sh.intel.com (HELO localhost) ([10.239.160.132]) by orsmga004.jf.intel.com with ESMTP; 17 Oct 2022 02:47:59 -0700 Date: Mon, 17 Oct 2022 17:53:34 +0800 From: Zhao Liu To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Daniel Vetter , Matthew Auld , Thomas =?iso-8859-1?Q?Hellstr=F6m?= , Nirmoy Das , Maarten Lankhorst , Chris Wilson , Christian =?iso-8859-1?Q?K=F6nig?= , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: Ira Weiny , "Fabio M. De Francesco" , Zhenyu Wang , Zhao Liu Subject: Re: [PATCH v3] x86/hyperv: Replace kmap() with kmap_local_page() Message-ID: References: <20221017093726.2070674-1-zhao1.liu@linux.intel.com> <20221017093726.2070674-11-zhao1.liu@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221017093726.2070674-11-zhao1.liu@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry, please ignore the last hyperv patch, I made a mistake. Zhao On Mon, Oct 17, 2022 at 05:37:26PM +0800, Zhao Liu wrote: > Date: Mon, 17 Oct 2022 17:37:26 +0800 > From: Zhao Liu > Subject: [PATCH v3] x86/hyperv: Replace kmap() with kmap_local_page() > X-Mailer: git-send-email 2.34.1 > > From: Zhao Liu > > kmap() is being deprecated in favor of kmap_local_page()[1]. > > There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap's pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. > > With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). > It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, the tasks can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. > > Since its use in hyperv/hv_init.c is safe, it should be preferred. > > Therefore, replace kmap() with kmap_local_page() in hyperv/hv_init.c. > > [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com > > Suggested-by: Ira Weiny > Suggested-by: Fabio M. De Francesco > Signed-off-by: Zhao Liu > > --- > Suggested by credits. > Ira: Referred to his task documentation and review comments. > Fabio: Stole some of his boiler plate commit message. > > --- > Changelog: > v2: > - Fix wrong incoming parameters in kunmap_local(); > - Add Fabio as suggester since I quoted his commit message. > > --- > arch/x86/hyperv/hv_init.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > index 3de6d8b53367..72fe46eb183f 100644 > --- a/arch/x86/hyperv/hv_init.c > +++ b/arch/x86/hyperv/hv_init.c > @@ -459,13 +459,13 @@ void __init hyperv_init(void) > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > pg = vmalloc_to_page(hv_hypercall_pg); > - dst = kmap(pg); > + dst = kmap_local_page(pg); > src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE, > MEMREMAP_WB); > BUG_ON(!(src && dst)); > memcpy(dst, src, HV_HYP_PAGE_SIZE); > memunmap(src); > - kunmap(pg); > + kunmap_local(dst); > } else { > hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg); > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > -- > 2.34.1 >