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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 89FCBC4708F for ; Tue, 1 Jun 2021 14:38:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F0EA613B1 for ; Tue, 1 Jun 2021 14:38:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234116AbhFAOkI (ORCPT ); Tue, 1 Jun 2021 10:40:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:53480 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233797AbhFAOkG (ORCPT ); Tue, 1 Jun 2021 10:40:06 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 73E7B61375; Tue, 1 Jun 2021 14:38:25 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lo5XD-004q07-As; Tue, 01 Jun 2021 15:38:23 +0100 Date: Tue, 01 Jun 2021 15:38:22 +0100 Message-ID: <87k0nd1wgx.wl-maz@kernel.org> From: Marc Zyngier To: Quentin Perret Cc: will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page In-Reply-To: <20210527125134.2116404-4-qperret@google.com> References: <20210527125134.2116404-1-qperret@google.com> <20210527125134.2116404-4-qperret@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: qperret@google.com, will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 27 May 2021 13:51:30 +0100, Quentin Perret wrote: > > The list_head member of struct hyp_page is only needed when the page is > attached to a free-list, which by definition implies the page is free. > As such, nothing prevents us from using the page itself to store the > list_head, hence reducing the size of the vmemmap. > > Signed-off-by: Quentin Perret > --- > arch/arm64/kvm/hyp/include/nvhe/memory.h | 1 - > arch/arm64/kvm/hyp/nvhe/page_alloc.c | 39 ++++++++++++++++++++---- > 2 files changed, 33 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > index fd78bde939ee..7691ab495eb4 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > @@ -12,7 +12,6 @@ struct hyp_page { > unsigned int refcount; > unsigned int order; > struct hyp_pool *pool; > - struct list_head node; > }; > > extern u64 __hyp_vmemmap; > diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > index 7ee882f36767..ce7379f1480b 100644 > --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c > +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > @@ -62,6 +62,34 @@ static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool, > > } > > +/* > + * Pages that are available for allocation are tracked in free-lists, so we use > + * the pages themselves to store the list nodes to avoid wasting space. As the > + * allocator always returns zeroed pages (which are zeroed on the hyp_put_page() > + * path to optimize allocation speed), we also need to clean-up the list node in > + * each page when we take it out of the list. > + */ > +static inline void page_remove_from_list(struct hyp_page *p) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); Nit: How about changing hyp_page_to_virt() so that it returns a convenient 'void *', and get rid of the ugly casts? > + > + __list_del_entry(node); > + memset(node, 0, sizeof(*node)); > +} > + > +static inline void page_add_to_list(struct hyp_page *p, struct list_head *head) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); > + > + INIT_LIST_HEAD(node); > + list_add_tail(node, head); > +} > + > +static inline struct hyp_page *node_to_page(struct list_head *node) > +{ > + return (struct hyp_page *)hyp_virt_to_page(node); Why is this cast necessary? If I'm not mistaken, hyp_vmemmap is already cast as a 'struct hyp_page *', so hyp_virt_to_page() should return the same type. > +} > + > static void __hyp_attach_page(struct hyp_pool *pool, > struct hyp_page *p) > { > @@ -83,14 +111,14 @@ static void __hyp_attach_page(struct hyp_pool *pool, > break; > > /* Take the buddy out of its list, and coallesce with @p */ > - list_del_init(&buddy->node); > + page_remove_from_list(buddy); > buddy->order = HYP_NO_ORDER; > p = min(p, buddy); > } > > /* Mark the new head, and insert it */ > p->order = order; > - list_add_tail(&p->node, &pool->free_area[order]); > + page_add_to_list(p, &pool->free_area[order]); > } > > static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > @@ -99,7 +127,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > { > struct hyp_page *buddy; > > - list_del_init(&p->node); > + page_remove_from_list(p); > while (p->order > order) { > /* > * The buddy of order n - 1 currently has HYP_NO_ORDER as it > @@ -110,7 +138,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > p->order--; > buddy = __find_buddy_nocheck(pool, p, p->order); > buddy->order = p->order; > - list_add_tail(&buddy->node, &pool->free_area[buddy->order]); > + page_add_to_list(buddy, &pool->free_area[buddy->order]); > } > > return p; > @@ -158,7 +186,7 @@ void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order) > } > > /* Extract it from the tree at the right order */ > - p = list_first_entry(&pool->free_area[i], struct hyp_page, node); > + p = node_to_page(pool->free_area[i].next); > p = __hyp_extract_page(pool, p, order); > > hyp_set_page_refcounted(p); > @@ -186,7 +214,6 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, > for (i = 0; i < nr_pages; i++) { > p[i].pool = pool; > p[i].order = 0; > - INIT_LIST_HEAD(&p[i].node); > hyp_set_page_refcounted(&p[i]); > } > > -- > 2.31.1.818.g46aad6cb9e-goog > > Thanks, M. -- Without deviation from the norm, progress is not possible. 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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 3C292C47080 for ; Tue, 1 Jun 2021 14:38:31 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id AB6D2613B1 for ; Tue, 1 Jun 2021 14:38:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB6D2613B1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 34DB44A3BF; Tue, 1 Jun 2021 10:38:30 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6Wq98E0gX3V9; Tue, 1 Jun 2021 10:38:28 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E89D54A32E; Tue, 1 Jun 2021 10:38:28 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id CF7244A32E for ; Tue, 1 Jun 2021 10:38:27 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id riOeleJY+GWs for ; Tue, 1 Jun 2021 10:38:26 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 8D3224A2E5 for ; Tue, 1 Jun 2021 10:38:26 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 73E7B61375; Tue, 1 Jun 2021 14:38:25 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lo5XD-004q07-As; Tue, 01 Jun 2021 15:38:23 +0100 Date: Tue, 01 Jun 2021 15:38:22 +0100 Message-ID: <87k0nd1wgx.wl-maz@kernel.org> From: Marc Zyngier To: Quentin Perret Subject: Re: [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page In-Reply-To: <20210527125134.2116404-4-qperret@google.com> References: <20210527125134.2116404-1-qperret@google.com> <20210527125134.2116404-4-qperret@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: qperret@google.com, will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kernel-team@android.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Thu, 27 May 2021 13:51:30 +0100, Quentin Perret wrote: > > The list_head member of struct hyp_page is only needed when the page is > attached to a free-list, which by definition implies the page is free. > As such, nothing prevents us from using the page itself to store the > list_head, hence reducing the size of the vmemmap. > > Signed-off-by: Quentin Perret > --- > arch/arm64/kvm/hyp/include/nvhe/memory.h | 1 - > arch/arm64/kvm/hyp/nvhe/page_alloc.c | 39 ++++++++++++++++++++---- > 2 files changed, 33 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > index fd78bde939ee..7691ab495eb4 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > @@ -12,7 +12,6 @@ struct hyp_page { > unsigned int refcount; > unsigned int order; > struct hyp_pool *pool; > - struct list_head node; > }; > > extern u64 __hyp_vmemmap; > diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > index 7ee882f36767..ce7379f1480b 100644 > --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c > +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > @@ -62,6 +62,34 @@ static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool, > > } > > +/* > + * Pages that are available for allocation are tracked in free-lists, so we use > + * the pages themselves to store the list nodes to avoid wasting space. As the > + * allocator always returns zeroed pages (which are zeroed on the hyp_put_page() > + * path to optimize allocation speed), we also need to clean-up the list node in > + * each page when we take it out of the list. > + */ > +static inline void page_remove_from_list(struct hyp_page *p) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); Nit: How about changing hyp_page_to_virt() so that it returns a convenient 'void *', and get rid of the ugly casts? > + > + __list_del_entry(node); > + memset(node, 0, sizeof(*node)); > +} > + > +static inline void page_add_to_list(struct hyp_page *p, struct list_head *head) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); > + > + INIT_LIST_HEAD(node); > + list_add_tail(node, head); > +} > + > +static inline struct hyp_page *node_to_page(struct list_head *node) > +{ > + return (struct hyp_page *)hyp_virt_to_page(node); Why is this cast necessary? If I'm not mistaken, hyp_vmemmap is already cast as a 'struct hyp_page *', so hyp_virt_to_page() should return the same type. > +} > + > static void __hyp_attach_page(struct hyp_pool *pool, > struct hyp_page *p) > { > @@ -83,14 +111,14 @@ static void __hyp_attach_page(struct hyp_pool *pool, > break; > > /* Take the buddy out of its list, and coallesce with @p */ > - list_del_init(&buddy->node); > + page_remove_from_list(buddy); > buddy->order = HYP_NO_ORDER; > p = min(p, buddy); > } > > /* Mark the new head, and insert it */ > p->order = order; > - list_add_tail(&p->node, &pool->free_area[order]); > + page_add_to_list(p, &pool->free_area[order]); > } > > static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > @@ -99,7 +127,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > { > struct hyp_page *buddy; > > - list_del_init(&p->node); > + page_remove_from_list(p); > while (p->order > order) { > /* > * The buddy of order n - 1 currently has HYP_NO_ORDER as it > @@ -110,7 +138,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > p->order--; > buddy = __find_buddy_nocheck(pool, p, p->order); > buddy->order = p->order; > - list_add_tail(&buddy->node, &pool->free_area[buddy->order]); > + page_add_to_list(buddy, &pool->free_area[buddy->order]); > } > > return p; > @@ -158,7 +186,7 @@ void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order) > } > > /* Extract it from the tree at the right order */ > - p = list_first_entry(&pool->free_area[i], struct hyp_page, node); > + p = node_to_page(pool->free_area[i].next); > p = __hyp_extract_page(pool, p, order); > > hyp_set_page_refcounted(p); > @@ -186,7 +214,6 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, > for (i = 0; i < nr_pages; i++) { > p[i].pool = pool; > p[i].order = 0; > - INIT_LIST_HEAD(&p[i].node); > hyp_set_page_refcounted(&p[i]); > } > > -- > 2.31.1.818.g46aad6cb9e-goog > > Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-14.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 CFAE1C4708F for ; Tue, 1 Jun 2021 14:39:51 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 95575613B1 for ; Tue, 1 Jun 2021 14:39:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95575613B1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=BMGHRaG4DpVxcZUJ51Gi+nLwpMHWIW/PJjaYZrzKt6s=; b=m1BK7MSNLqtVtT t07KQnlpju14umPLHcTbSgiyX1l3o4GEd+zZ+XFY45RrNcXk5QMdl9g/4D+Y31xY5c1r5qHfsp90E CqvesmT/G3vSGe0UZ8qw0fYTEoEcYM8AXGmKvDTDzbbl02yzotKwP7ngduyVypEw+ZJBfJ+GwPCph CcXENTNU7quizd1gWt7zu7DpZsv2Zs1U2oEEHMzxd1vkEF5cBHf5SyQEzoqxQjOh3CcbB910ZEky5 Aumt35MB1IRxi8wL4UI6KnM14oO7H721TO1cN1iVM8MIb5zun5axq0MTmRanMfIrdlNLVPDwJfXXB HJjrenvC28oqheW4Tt7Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lo5XJ-00H08Q-M9; Tue, 01 Jun 2021 14:38:29 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lo5XF-00H07X-Uk for linux-arm-kernel@lists.infradead.org; Tue, 01 Jun 2021 14:38:27 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 73E7B61375; Tue, 1 Jun 2021 14:38:25 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lo5XD-004q07-As; Tue, 01 Jun 2021 15:38:23 +0100 Date: Tue, 01 Jun 2021 15:38:22 +0100 Message-ID: <87k0nd1wgx.wl-maz@kernel.org> From: Marc Zyngier To: Quentin Perret Cc: will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page In-Reply-To: <20210527125134.2116404-4-qperret@google.com> References: <20210527125134.2116404-1-qperret@google.com> <20210527125134.2116404-4-qperret@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: qperret@google.com, will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210601_073826_057159_EBE8726C X-CRM114-Status: GOOD ( 37.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 27 May 2021 13:51:30 +0100, Quentin Perret wrote: > > The list_head member of struct hyp_page is only needed when the page is > attached to a free-list, which by definition implies the page is free. > As such, nothing prevents us from using the page itself to store the > list_head, hence reducing the size of the vmemmap. > > Signed-off-by: Quentin Perret > --- > arch/arm64/kvm/hyp/include/nvhe/memory.h | 1 - > arch/arm64/kvm/hyp/nvhe/page_alloc.c | 39 ++++++++++++++++++++---- > 2 files changed, 33 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > index fd78bde939ee..7691ab495eb4 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > @@ -12,7 +12,6 @@ struct hyp_page { > unsigned int refcount; > unsigned int order; > struct hyp_pool *pool; > - struct list_head node; > }; > > extern u64 __hyp_vmemmap; > diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > index 7ee882f36767..ce7379f1480b 100644 > --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c > +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c > @@ -62,6 +62,34 @@ static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool, > > } > > +/* > + * Pages that are available for allocation are tracked in free-lists, so we use > + * the pages themselves to store the list nodes to avoid wasting space. As the > + * allocator always returns zeroed pages (which are zeroed on the hyp_put_page() > + * path to optimize allocation speed), we also need to clean-up the list node in > + * each page when we take it out of the list. > + */ > +static inline void page_remove_from_list(struct hyp_page *p) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); Nit: How about changing hyp_page_to_virt() so that it returns a convenient 'void *', and get rid of the ugly casts? > + > + __list_del_entry(node); > + memset(node, 0, sizeof(*node)); > +} > + > +static inline void page_add_to_list(struct hyp_page *p, struct list_head *head) > +{ > + struct list_head *node = (struct list_head *)hyp_page_to_virt(p); > + > + INIT_LIST_HEAD(node); > + list_add_tail(node, head); > +} > + > +static inline struct hyp_page *node_to_page(struct list_head *node) > +{ > + return (struct hyp_page *)hyp_virt_to_page(node); Why is this cast necessary? If I'm not mistaken, hyp_vmemmap is already cast as a 'struct hyp_page *', so hyp_virt_to_page() should return the same type. > +} > + > static void __hyp_attach_page(struct hyp_pool *pool, > struct hyp_page *p) > { > @@ -83,14 +111,14 @@ static void __hyp_attach_page(struct hyp_pool *pool, > break; > > /* Take the buddy out of its list, and coallesce with @p */ > - list_del_init(&buddy->node); > + page_remove_from_list(buddy); > buddy->order = HYP_NO_ORDER; > p = min(p, buddy); > } > > /* Mark the new head, and insert it */ > p->order = order; > - list_add_tail(&p->node, &pool->free_area[order]); > + page_add_to_list(p, &pool->free_area[order]); > } > > static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > @@ -99,7 +127,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > { > struct hyp_page *buddy; > > - list_del_init(&p->node); > + page_remove_from_list(p); > while (p->order > order) { > /* > * The buddy of order n - 1 currently has HYP_NO_ORDER as it > @@ -110,7 +138,7 @@ static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, > p->order--; > buddy = __find_buddy_nocheck(pool, p, p->order); > buddy->order = p->order; > - list_add_tail(&buddy->node, &pool->free_area[buddy->order]); > + page_add_to_list(buddy, &pool->free_area[buddy->order]); > } > > return p; > @@ -158,7 +186,7 @@ void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order) > } > > /* Extract it from the tree at the right order */ > - p = list_first_entry(&pool->free_area[i], struct hyp_page, node); > + p = node_to_page(pool->free_area[i].next); > p = __hyp_extract_page(pool, p, order); > > hyp_set_page_refcounted(p); > @@ -186,7 +214,6 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, > for (i = 0; i < nr_pages; i++) { > p[i].pool = pool; > p[i].order = 0; > - INIT_LIST_HEAD(&p[i].node); > hyp_set_page_refcounted(&p[i]); > } > > -- > 2.31.1.818.g46aad6cb9e-goog > > Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel