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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 A35C9C4363A for ; Fri, 23 Oct 2020 16:30:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42DBD21D47 for ; Fri, 23 Oct 2020 16:30:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OywPTgum" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751542AbgJWQaf (ORCPT ); Fri, 23 Oct 2020 12:30:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:39074 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751516AbgJWQae (ORCPT ); Fri, 23 Oct 2020 12:30:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603470632; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=r0u+Is6JwRmmXFJMLeCPF6/HpKU+rnLQL1ih5VNFzJI=; b=OywPTgum9W6QTHy+stt66irplj7v7ZSmZs8XTPF59llWhGQtl0yBmg9SHX0ePAcMXqubR8 cqDyxF5TnQ99BTugRYP9B+tlOzYL0g3eKiLzRk0HWG0goWuv8G7M5dQJbq7SNEcV5+7rM5 dV+ZTp6OsjvCckV9y5y3I66qGb4xUmI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-108-ws4dslFJOmq9yo_MsSRQwQ-1; Fri, 23 Oct 2020 12:30:29 -0400 X-MC-Unique: ws4dslFJOmq9yo_MsSRQwQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A7E67CF983; Fri, 23 Oct 2020 16:30:27 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4842A5D9E2; Fri, 23 Oct 2020 16:30:27 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: bgardon@google.com Subject: [PATCH 05/22] kvm: x86/mmu: Introduce tdp_iter Date: Fri, 23 Oct 2020 12:30:07 -0400 Message-Id: <20201023163024.2765558-6-pbonzini@redhat.com> In-Reply-To: <20201023163024.2765558-1-pbonzini@redhat.com> References: <20201023163024.2765558-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Ben Gardon The TDP iterator implements a pre-order traversal of a TDP paging structure. This iterator will be used in future patches to create an efficient implementation of the KVM MMU for the TDP case. Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell machine. This series introduced no new failures. This series can be viewed in Gerrit at: https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538 Signed-off-by: Ben Gardon Signed-off-by: Paolo Bonzini --- arch/x86/kvm/Makefile | 2 +- arch/x86/kvm/mmu/tdp_iter.c | 177 ++++++++++++++++++++++++++++++++++++ arch/x86/kvm/mmu/tdp_iter.h | 56 ++++++++++++ 3 files changed, 234 insertions(+), 1 deletion(-) create mode 100644 arch/x86/kvm/mmu/tdp_iter.c create mode 100644 arch/x86/kvm/mmu/tdp_iter.h diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile index 66aa24f5e2db..a5dd4e5970f8 100644 --- a/arch/x86/kvm/Makefile +++ b/arch/x86/kvm/Makefile @@ -16,7 +16,7 @@ kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o kvm-y += x86.o emulate.o i8259.o irq.o lapic.o \ i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \ hyperv.o debugfs.o mmu/mmu.o mmu/page_track.o \ - mmu/spte.o + mmu/spte.o mmu/tdp_iter.o kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \ vmx/evmcs.o vmx/nested.o vmx/posted_intr.o diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c new file mode 100644 index 000000000000..ad2184cb054c --- /dev/null +++ b/arch/x86/kvm/mmu/tdp_iter.c @@ -0,0 +1,177 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "mmu_internal.h" +#include "tdp_iter.h" +#include "spte.h" + +/* + * Recalculates the pointer to the SPTE for the current GFN and level and + * reread the SPTE. + */ +static void tdp_iter_refresh_sptep(struct tdp_iter *iter) +{ + iter->sptep = iter->pt_path[iter->level - 1] + + SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level); + iter->old_spte = READ_ONCE(*iter->sptep); +} + +static gfn_t round_gfn_for_level(gfn_t gfn, int level) +{ + return gfn & -KVM_PAGES_PER_HPAGE(level); +} + +/* + * Sets a TDP iterator to walk a pre-order traversal of the paging structure + * rooted at root_pt, starting with the walk to translate goal_gfn. + */ +void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level, + int min_level, gfn_t goal_gfn) +{ + WARN_ON(root_level < 1); + WARN_ON(root_level > PT64_ROOT_MAX_LEVEL); + + iter->goal_gfn = goal_gfn; + iter->root_level = root_level; + iter->min_level = min_level; + iter->level = root_level; + iter->pt_path[iter->level - 1] = root_pt; + + iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level); + tdp_iter_refresh_sptep(iter); + + iter->valid = true; +} + +/* + * Given an SPTE and its level, returns a pointer containing the host virtual + * address of the child page table referenced by the SPTE. Returns null if + * there is no such entry. + */ +u64 *spte_to_child_pt(u64 spte, int level) +{ + /* + * There's no child entry if this entry isn't present or is a + * last-level entry. + */ + if (!is_shadow_present_pte(spte) || is_last_spte(spte, level)) + return NULL; + + return __va(spte_to_pfn(spte) << PAGE_SHIFT); +} + +/* + * Steps down one level in the paging structure towards the goal GFN. Returns + * true if the iterator was able to step down a level, false otherwise. + */ +static bool try_step_down(struct tdp_iter *iter) +{ + u64 *child_pt; + + if (iter->level == iter->min_level) + return false; + + /* + * Reread the SPTE before stepping down to avoid traversing into page + * tables that are no longer linked from this entry. + */ + iter->old_spte = READ_ONCE(*iter->sptep); + + child_pt = spte_to_child_pt(iter->old_spte, iter->level); + if (!child_pt) + return false; + + iter->level--; + iter->pt_path[iter->level - 1] = child_pt; + iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level); + tdp_iter_refresh_sptep(iter); + + return true; +} + +/* + * Steps to the next entry in the current page table, at the current page table + * level. The next entry could point to a page backing guest memory or another + * page table, or it could be non-present. Returns true if the iterator was + * able to step to the next entry in the page table, false if the iterator was + * already at the end of the current page table. + */ +static bool try_step_side(struct tdp_iter *iter) +{ + /* + * Check if the iterator is already at the end of the current page + * table. + */ + if (SHADOW_PT_INDEX(iter->gfn << PAGE_SHIFT, iter->level) == + (PT64_ENT_PER_PAGE - 1)) + return false; + + iter->gfn += KVM_PAGES_PER_HPAGE(iter->level); + iter->goal_gfn = iter->gfn; + iter->sptep++; + iter->old_spte = READ_ONCE(*iter->sptep); + + return true; +} + +/* + * Tries to traverse back up a level in the paging structure so that the walk + * can continue from the next entry in the parent page table. Returns true on a + * successful step up, false if already in the root page. + */ +static bool try_step_up(struct tdp_iter *iter) +{ + if (iter->level == iter->root_level) + return false; + + iter->level++; + iter->gfn = round_gfn_for_level(iter->gfn, iter->level); + tdp_iter_refresh_sptep(iter); + + return true; +} + +/* + * Step to the next SPTE in a pre-order traversal of the paging structure. + * To get to the next SPTE, the iterator either steps down towards the goal + * GFN, if at a present, non-last-level SPTE, or over to a SPTE mapping a + * highter GFN. + * + * The basic algorithm is as follows: + * 1. If the current SPTE is a non-last-level SPTE, step down into the page + * table it points to. + * 2. If the iterator cannot step down, it will try to step to the next SPTE + * in the current page of the paging structure. + * 3. If the iterator cannot step to the next entry in the current page, it will + * try to step up to the parent paging structure page. In this case, that + * SPTE will have already been visited, and so the iterator must also step + * to the side again. + */ +void tdp_iter_next(struct tdp_iter *iter) +{ + if (try_step_down(iter)) + return; + + do { + if (try_step_side(iter)) + return; + } while (try_step_up(iter)); + iter->valid = false; +} + +/* + * Restart the walk over the paging structure from the root, starting from the + * highest gfn the iterator had previously reached. Assumes that the entire + * paging structure, except the root page, may have been completely torn down + * and rebuilt. + */ +void tdp_iter_refresh_walk(struct tdp_iter *iter) +{ + gfn_t goal_gfn = iter->goal_gfn; + + if (iter->gfn > goal_gfn) + goal_gfn = iter->gfn; + + tdp_iter_start(iter, iter->pt_path[iter->root_level - 1], + iter->root_level, iter->min_level, goal_gfn); +} + diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h new file mode 100644 index 000000000000..d629a53e1b73 --- /dev/null +++ b/arch/x86/kvm/mmu/tdp_iter.h @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0 + +#ifndef __KVM_X86_MMU_TDP_ITER_H +#define __KVM_X86_MMU_TDP_ITER_H + +#include + +#include "mmu.h" + +/* + * A TDP iterator performs a pre-order walk over a TDP paging structure. + */ +struct tdp_iter { + /* + * The iterator will traverse the paging structure towards the mapping + * for this GFN. + */ + gfn_t goal_gfn; + /* Pointers to the page tables traversed to reach the current SPTE */ + u64 *pt_path[PT64_ROOT_MAX_LEVEL]; + /* A pointer to the current SPTE */ + u64 *sptep; + /* The lowest GFN mapped by the current SPTE */ + gfn_t gfn; + /* The level of the root page given to the iterator */ + int root_level; + /* The lowest level the iterator should traverse to */ + int min_level; + /* The iterator's current level within the paging structure */ + int level; + /* A snapshot of the value at sptep */ + u64 old_spte; + /* + * Whether the iterator has a valid state. This will be false if the + * iterator walks off the end of the paging structure. + */ + bool valid; +}; + +/* + * Iterates over every SPTE mapping the GFN range [start, end) in a + * preorder traversal. + */ +#define for_each_tdp_pte(iter, root, root_level, start, end) \ + for (tdp_iter_start(&iter, root, root_level, PG_LEVEL_4K, start); \ + iter.valid && iter.gfn < end; \ + tdp_iter_next(&iter)) + +u64 *spte_to_child_pt(u64 pte, int level); + +void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level, + int min_level, gfn_t goal_gfn); +void tdp_iter_next(struct tdp_iter *iter); +void tdp_iter_refresh_walk(struct tdp_iter *iter); + +#endif /* __KVM_X86_MMU_TDP_ITER_H */ -- 2.26.2