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 52D69C4332F for ; Mon, 14 Nov 2022 18:48:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236525AbiKNSsO (ORCPT ); Mon, 14 Nov 2022 13:48:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235954AbiKNSsN (ORCPT ); Mon, 14 Nov 2022 13:48:13 -0500 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD23613F75 for ; Mon, 14 Nov 2022 10:48:12 -0800 (PST) Date: Mon, 14 Nov 2022 18:48:04 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1668451689; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Ql8zFw/DxEYIf4IQ7KYe8Xa1QN1s9FqjeGphu6RWQE0=; b=fZ0/Ii6j2iJMk+5Ifc1knRSHKvjiHHn3ogpu2jcYbK+f0t4CQJZkX/9gpvgZZYcdEMPy7v RCtRu/x1mWpxQxYTS19afbHKVMlExyhZrat4Ov8c4n1sLfOguH0PbCXbOEPfoRoILSq5Qf 6AO6nic/6sRSOEy/ku4/33HGFBSVpEw= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Ricardo Koller Cc: pbonzini@redhat.com, maz@kernel.org, dmatlack@google.com, qperret@google.com, catalin.marinas@arm.com, andrew.jones@linux.dev, seanjc@google.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, eric.auger@redhat.com, gshan@redhat.com, reijiw@google.com, rananta@google.com, bgardon@google.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, ricarkol@gmail.com Subject: Re: [RFC PATCH 02/12] KVM: arm64: Allow visiting block PTEs in post-order Message-ID: References: <20221112081714.2169495-1-ricarkol@google.com> <20221112081714.2169495-3-ricarkol@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221112081714.2169495-3-ricarkol@google.com> X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Sat, Nov 12, 2022 at 08:17:04AM +0000, Ricardo Koller wrote: > The page table walker does not visit block PTEs in post-order. But there > are some cases where doing so would be beneficial, for example: breaking a > 1G block PTE into a full tree in post-order avoids visiting the new tree. > > Allow post order visits of block PTEs. This will be used in a subsequent > commit for eagerly breaking huge pages. > > Signed-off-by: Ricardo Koller > --- > arch/arm64/include/asm/kvm_pgtable.h | 4 ++-- > arch/arm64/kvm/hyp/nvhe/setup.c | 2 +- > arch/arm64/kvm/hyp/pgtable.c | 25 ++++++++++++------------- > 3 files changed, 15 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index e2edeed462e8..d2e4a5032146 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -255,7 +255,7 @@ struct kvm_pgtable { > * entries. > * @KVM_PGTABLE_WALK_TABLE_PRE: Visit table entries before their > * children. > - * @KVM_PGTABLE_WALK_TABLE_POST: Visit table entries after their > + * @KVM_PGTABLE_WALK_POST: Visit leaf or table entries after their > * children. It is not immediately obvious from this change alone that promoting the post-order traversal of every walker to cover leaf + table PTEs is safe. Have you considered using a flag for just leaf post-order visits? -- Thanks, Oliver