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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 17F40C4338F for ; Tue, 3 Aug 2021 05:03:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE08060D07 for ; Tue, 3 Aug 2021 05:03:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233748AbhHCFDb (ORCPT ); Tue, 3 Aug 2021 01:03:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33334 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229753AbhHCFD3 (ORCPT ); Tue, 3 Aug 2021 01:03:29 -0400 Received: from mail-ot1-x334.google.com (mail-ot1-x334.google.com [IPv6:2607:f8b0:4864:20::334]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B1EEC06175F for ; Mon, 2 Aug 2021 22:03:19 -0700 (PDT) Received: by mail-ot1-x334.google.com with SMTP id v8-20020a0568301bc8b02904d5b4e5ca3aso7447710ota.13 for ; Mon, 02 Aug 2021 22:03:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=98m49kM51gXXQwk6EzBddK2TZzu06e6NOrKKSkFgLXM=; b=JBfRN5uUGJv1mXH50K1CUMtDQM796k7tGX2Ggs3sEatCxVZhKBAtXSgvWVQYe793T+ 003e95gjoA3OzMjjHFsMb0rlP1AnnVwDbrdL87tbbPt4M3Tgv6pd1Oi3uu4AawLHtTt/ LfxpBm0bd/2e42IQOKMsrniKeY7x4/1DBISSuyzW/bYl3ihzEtBnZWhjjr+fB7XKS2tL C0sjEML/9uy5Fou5GMaLDw+ItaHpAdsWgNmzppUMP2hoLnwzQT+exRn1U90Mr6Qt0d77 II3+ILcfc6/Ht8xDPjvcu4IWmoDcutECmD9qPd8SjUofuZuMpfo8LMghTHZJxYCQ27xh ymkw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=98m49kM51gXXQwk6EzBddK2TZzu06e6NOrKKSkFgLXM=; b=uc3zYg48K8XRwH06fUqBVwHBNSN9k05OIKF7sh4kn7QaJzXLJ8LlJc4vg1vOkgOCoh uVfrhaqyP9Lr3CIchoTPurGWFwaz1NZHJb6uoVbs834GmkAnf2fwfEq0gKTali6betjm jMjtC50JCJLj2e6ldl4pkz8bw4ISfTupskFlRbfu9vsr9yChsbqI40O9pGfpLcJavZNC NzDqc56wymHKNLpkwbpjN8JnKzaI8Bcgc6CdzdF/iznmPC20Gka7veUBgsr8Fx53WBGK WAUfwxfYKi80OM7v3qfbYAFW2dojYxWXXRbz7e7wT384PjMR3H1r+X/qgps7sigppHNo MV6g== X-Gm-Message-State: AOAM530e2eVPEo8f/8IirgJI8anoffl7OF2bYu3Hikhc7hf+Xo+2aTrt jSgHTTkLbPe/1/588kH0V107ZxoE8PbMYkRm+kwfxQ== X-Google-Smtp-Source: ABdhPJxUZ3uaAUbN+2nQwNL5VyZUDFvbxFFeJtlu36GNKbf5VdioZ67EaWSYprJBEZoIRbrNocdm8Hwh3Z7MWKDhLCw= X-Received: by 2002:a9d:202d:: with SMTP id n42mr474563ota.52.1627966998377; Mon, 02 Aug 2021 22:03:18 -0700 (PDT) MIME-Version: 1.0 References: <20210729132818.4091769-1-qperret@google.com> <20210729132818.4091769-18-qperret@google.com> In-Reply-To: <20210729132818.4091769-18-qperret@google.com> From: Fuad Tabba Date: Tue, 3 Aug 2021 07:02:42 +0200 Message-ID: Subject: Re: [PATCH v3 17/21] KVM: arm64: Mark host bss and rodata section as shared To: Quentin Perret Cc: maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, ardb@kernel.org, qwandor@google.com, dbrazdil@google.com, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Quentin, On Thu, Jul 29, 2021 at 3:29 PM Quentin Perret wrote: > > As the hypervisor maps the host's .bss and .rodata sections in its > stage-1, make sure to tag them as shared in hyp and host page-tables. > > But since the hypervisor relies on the presence of these mappings, we > cannot let the host in complete control of the memory regions -- it > must not unshare or donate them to another entity for example. To > prevent this, let's transfer the ownership of those ranges to the > hypervisor itself, and share the pages back with the host. > > Signed-off-by: Quentin Perret > --- > arch/arm64/kvm/hyp/nvhe/setup.c | 82 +++++++++++++++++++++++++++++---- > 1 file changed, 74 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c > index 0b574d106519..7f557b264f62 100644 > --- a/arch/arm64/kvm/hyp/nvhe/setup.c > +++ b/arch/arm64/kvm/hyp/nvhe/setup.c > @@ -58,6 +58,7 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > { > void *start, *end, *virt = hyp_phys_to_virt(phys); > unsigned long pgt_size = hyp_s1_pgtable_pages() << PAGE_SHIFT; > + enum kvm_pgtable_prot prot; > int ret, i; > > /* Recreate the hyp page-table using the early page allocator */ > @@ -83,10 +84,6 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > if (ret) > return ret; > > - ret = pkvm_create_mappings(__start_rodata, __end_rodata, PAGE_HYP_RO); > - if (ret) > - return ret; > - > ret = pkvm_create_mappings(__hyp_rodata_start, __hyp_rodata_end, PAGE_HYP_RO); > if (ret) > return ret; > @@ -95,10 +92,6 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > if (ret) > return ret; > > - ret = pkvm_create_mappings(__hyp_bss_end, __bss_stop, PAGE_HYP_RO); > - if (ret) > - return ret; > - > ret = pkvm_create_mappings(virt, virt + size, PAGE_HYP); > if (ret) > return ret; > @@ -117,6 +110,24 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size, > return ret; > } > > + /* > + * Map the host's .bss and .rodata sections RO in the hypervisor, but > + * transfer the ownerhsip from the host to the hypervisor itself to > + * make sure it can't be donated or shared with another entity. nit: ownerhsip -> ownership > + * > + * The ownership transtion requires matching changes in the host nit: transtion -> transition > + * stage-2. This will done later (see finalize_host_mappings()) once the nit: will done -> will be done > + * hyp_vmemmap is addressable. > + */ > + prot = pkvm_mkstate(PAGE_HYP_RO, PKVM_PAGE_SHARED_OWNED); > + ret = pkvm_create_mappings(__start_rodata, __end_rodata, prot); > + if (ret) > + return ret; > + > + ret = pkvm_create_mappings(__hyp_bss_end, __bss_stop, prot); nit: for clarity, I wonder if it might be good to create an alias of __hyp_bss_end as __bss_start or something. When it's been moved here, it sticks out a bit more and makes the reader wonder about the significance of __hyp_bss_end. > + if (ret) > + return ret; > + > return 0; > } > > @@ -148,6 +159,57 @@ static void hpool_put_page(void *addr) > hyp_put_page(&hpool, addr); > } > > +static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level, > + kvm_pte_t *ptep, > + enum kvm_pgtable_walk_flags flag, > + void * const arg) > +{ > + enum kvm_pgtable_prot prot; > + enum pkvm_page_state state; > + kvm_pte_t pte = *ptep; > + phys_addr_t phys; > + > + if (!kvm_pte_valid(pte)) > + return 0; > + > + if (level != (KVM_PGTABLE_MAX_LEVELS - 1)) > + return -EINVAL; I know that it's not in scope here, but I'm wondering whether we should be checking for KVM_PTE_TYPE_PAGE instead of the level. Maybe it would be good to have a helper somewhere for all these checks both for clarity and to ensure that nothing has gone wrong with the pte. > + > + phys = kvm_pte_to_phys(pte); > + if (!addr_is_memory(phys)) > + return 0; > + > + /* > + * Adjust the host stage-2 mappings to match the ownership attributes > + * configured in the hypervisor stage-1. > + */ > + state = pkvm_getstate(kvm_pgtable_hyp_pte_prot(pte)); > + switch (state) { > + case PKVM_PAGE_OWNED: > + return host_stage2_set_owner_locked(phys, phys + PAGE_SIZE, pkvm_hyp_id); > + case PKVM_PAGE_SHARED_OWNED: > + prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_BORROWED); > + break; > + case PKVM_PAGE_SHARED_BORROWED: > + prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED); > + break; > + default: > + return -EINVAL; > + } > + > + return host_stage2_idmap_locked(phys, phys + PAGE_SIZE, prot); > +} > + > +static int finalize_host_mappings(void) > +{ > + struct kvm_pgtable_walker walker = { > + .cb = finalize_host_mappings_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + }; > + > + return kvm_pgtable_walk(&pkvm_pgtable, 0, BIT(pkvm_pgtable.ia_bits), &walker); > +} > + > void __noreturn __pkvm_init_finalise(void) > { > struct kvm_host_data *host_data = this_cpu_ptr(&kvm_host_data); > @@ -167,6 +229,10 @@ void __noreturn __pkvm_init_finalise(void) > if (ret) > goto out; > > + ret = finalize_host_mappings(); > + if (ret) > + goto out; > + > pkvm_pgtable_mm_ops = (struct kvm_pgtable_mm_ops) { > .zalloc_page = hyp_zalloc_hyp_page, > .phys_to_virt = hyp_phys_to_virt, > -- > 2.32.0.432.gabb21c7263-goog > Thanks, /fuad