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=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 39F2DC4338F for ; Tue, 10 Aug 2021 04:44:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 224C161051 for ; Tue, 10 Aug 2021 04:44:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236234AbhHJEo1 (ORCPT ); Tue, 10 Aug 2021 00:44:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237275AbhHJEoS (ORCPT ); Tue, 10 Aug 2021 00:44:18 -0400 Received: from mail-ot1-x335.google.com (mail-ot1-x335.google.com [IPv6:2607:f8b0:4864:20::335]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC2E1C0613D3 for ; Mon, 9 Aug 2021 21:43:56 -0700 (PDT) Received: by mail-ot1-x335.google.com with SMTP id c23-20020a0568301af7b029050cd611fb72so2018170otd.3 for ; Mon, 09 Aug 2021 21:43:56 -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=6hIn+VGKvusb6b7sO/wOtxTZw8L+KXVHNSnzIuHc/pE=; b=fgUKRrd2ALAqp5eIVnbfIwegrCVM7UjXuYYeKg5JzYTFO4yhEuZxKBoFf7/CaFqO2g fmMPKFH/FgKPJ8Qqm2BtlpJYOGpNpvk1mZNllYN8c7Js8i2Tm6Lg+uvTnKrYNh/bxUme vVTnmf0YmJbbVqIzNWsVCfTOGcBLcuJ4DwMObX00w4mzouCFATn769zSycJneHKNqg9B xx13ceImQW+CWfxFxvvyKTp/rLwqXKSSr79URSVZkSL7f1CVpdHDOLTFbtkJaTq22Ukr u6oWkTp8+8VJ0BKoQm0GgwWWpvHcXvUtSZ8diIP5DvfP2tPgd4r5Y46eYZkF2r6L79+x I/QA== 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=6hIn+VGKvusb6b7sO/wOtxTZw8L+KXVHNSnzIuHc/pE=; b=JS0J1BZmL8wXIAnZU7mvVMzBwhy/dqYJYa/KXkkXnlhm4BCnNSWXSgZXThN3km+fWl pzjQrJKFkbPlQ+cM9TWnlX71s8iCFOEg6WXMkN5exQPMakjfWmDFayRK2FU1y8LwTlE4 w7vd6i3HGfyNRk3aSb+k9ORSn2oYhF/I6+FBahHzMtFel/1gKgu0t3j04/BnEFQdzgnb +OhWof07sdToJN9blHJaS3Bjjz6TYZNdENM2e553RysNJbxydYFRsOhmCJ75S/PUX0fk FOygFFEWJR5gtL6MnaYlmwR2WtHFrquDAei4MAw3k5aFnepul7h7rWY+x7OHbBchWU2o 7cWw== X-Gm-Message-State: AOAM533fqa/opzkgdI8C6CCfGWSjAXLrHfZHUPiHSv5didmECHyIgeND waHkr4O/QY4iWJ7Xtsn3PAFJUOGXei4CKDW8G6x1xQ== X-Google-Smtp-Source: ABdhPJzOF1Ld2lX/FTRPRpblwYqA+D2k2EFUDV3ETiQrYV+LzoFPd9b9VW+kK9Hds3CzrO0et0cLy6KDLuUHG0ywX4c= X-Received: by 2002:a9d:7359:: with SMTP id l25mr993791otk.52.1628570636085; Mon, 09 Aug 2021 21:43:56 -0700 (PDT) MIME-Version: 1.0 References: <20210809152448.1810400-1-qperret@google.com> <20210809152448.1810400-21-qperret@google.com> In-Reply-To: <20210809152448.1810400-21-qperret@google.com> From: Fuad Tabba Date: Tue, 10 Aug 2021 06:43:20 +0200 Message-ID: Subject: Re: [PATCH v4 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode 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 Mon, Aug 9, 2021 at 5:25 PM Quentin Perret wrote: > > The host kernel is currently able to change EL2 stage-1 mappings without > restrictions thanks to the __pkvm_create_mappings() hypercall. But in a > world where the host is no longer part of the TCB, this clearly poses a > problem. > > To fix this, introduce a new hypercall to allow the host to share a > physical memory page with the hypervisor, and remove the > __pkvm_create_mappings() variant. The new hypercall implements > ownership and permission checks before allowing the sharing operation, > and it annotates the shared page in the hypervisor stage-1 and host > stage-2 page-tables. > > Signed-off-by: Quentin Perret > --- Reviewed-by: Fuad Tabba Thanks, /fuad > arch/arm64/include/asm/kvm_asm.h | 2 +- > arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + > arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 +-- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 88 +++++++++++++++++++ > arch/arm64/kvm/mmu.c | 28 +++++- > 5 files changed, 118 insertions(+), 12 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h > index 432a9ea1f02e..aed2aa61766a 100644 > --- a/arch/arm64/include/asm/kvm_asm.h > +++ b/arch/arm64/include/asm/kvm_asm.h > @@ -59,7 +59,7 @@ > #define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13 > #define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14 > #define __KVM_HOST_SMCCC_FUNC___pkvm_init 15 > -#define __KVM_HOST_SMCCC_FUNC___pkvm_create_mappings 16 > +#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16 > #define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17 > #define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18 > #define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19 > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > index 0118527b07b0..03e604f842e2 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > @@ -49,6 +49,7 @@ extern struct host_kvm host_kvm; > extern const u8 pkvm_hyp_id; > > int __pkvm_prot_finalize(void); > +int __pkvm_host_share_hyp(u64 pfn); > > bool addr_is_memory(phys_addr_t phys); > int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot); > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > index 7900d5b66ba3..2da6aa8da868 100644 > --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > @@ -140,14 +140,11 @@ static void handle___pkvm_cpu_set_vector(struct kvm_cpu_context *host_ctxt) > cpu_reg(host_ctxt, 1) = pkvm_cpu_set_vector(slot); > } > > -static void handle___pkvm_create_mappings(struct kvm_cpu_context *host_ctxt) > +static void handle___pkvm_host_share_hyp(struct kvm_cpu_context *host_ctxt) > { > - DECLARE_REG(unsigned long, start, host_ctxt, 1); > - DECLARE_REG(unsigned long, size, host_ctxt, 2); > - DECLARE_REG(unsigned long, phys, host_ctxt, 3); > - DECLARE_REG(enum kvm_pgtable_prot, prot, host_ctxt, 4); > + DECLARE_REG(u64, pfn, host_ctxt, 1); > > - cpu_reg(host_ctxt, 1) = __pkvm_create_mappings(start, size, phys, prot); > + cpu_reg(host_ctxt, 1) = __pkvm_host_share_hyp(pfn); > } > > static void handle___pkvm_create_private_mapping(struct kvm_cpu_context *host_ctxt) > @@ -185,7 +182,7 @@ static const hcall_t host_hcall[] = { > HANDLE_FUNC(__vgic_v3_restore_aprs), > HANDLE_FUNC(__pkvm_init), > HANDLE_FUNC(__pkvm_cpu_set_vector), > - HANDLE_FUNC(__pkvm_create_mappings), > + HANDLE_FUNC(__pkvm_host_share_hyp), > HANDLE_FUNC(__pkvm_create_private_mapping), > HANDLE_FUNC(__pkvm_prot_finalize), > }; > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > index 2991dc6996b9..8165390d3ec9 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -339,6 +339,94 @@ static int host_stage2_idmap(u64 addr) > return ret; > } > > +static inline bool check_prot(enum kvm_pgtable_prot prot, > + enum kvm_pgtable_prot required, > + enum kvm_pgtable_prot denied) > +{ > + return (prot & (required | denied)) == required; > +} > + > +int __pkvm_host_share_hyp(u64 pfn) > +{ > + phys_addr_t addr = hyp_pfn_to_phys(pfn); > + enum kvm_pgtable_prot prot, cur; > + void *virt = __hyp_va(addr); > + enum pkvm_page_state state; > + kvm_pte_t pte; > + int ret; > + > + if (!addr_is_memory(addr)) > + return -EINVAL; > + > + hyp_spin_lock(&host_kvm.lock); > + hyp_spin_lock(&pkvm_pgd_lock); > + > + ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, NULL); > + if (ret) > + goto unlock; > + if (!pte) > + goto map_shared; > + > + /* > + * Check attributes in the host stage-2 PTE. We need the page to be: > + * - mapped RWX as we're sharing memory; > + * - not borrowed, as that implies absence of ownership. > + * Otherwise, we can't let it got through > + */ > + cur = kvm_pgtable_stage2_pte_prot(pte); > + prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED); > + if (!check_prot(cur, PKVM_HOST_MEM_PROT, prot)) { > + ret = -EPERM; > + goto unlock; > + } > + > + state = pkvm_getstate(cur); > + if (state == PKVM_PAGE_OWNED) > + goto map_shared; > + > + /* > + * Tolerate double-sharing the same page, but this requires > + * cross-checking the hypervisor stage-1. > + */ > + if (state != PKVM_PAGE_SHARED_OWNED) { > + ret = -EPERM; > + goto unlock; > + } > + > + ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, NULL); > + if (ret) > + goto unlock; > + > + /* > + * If the page has been shared with the hypervisor, it must be > + * already mapped as SHARED_BORROWED in its stage-1. > + */ > + cur = kvm_pgtable_hyp_pte_prot(pte); > + prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED); > + if (!check_prot(cur, prot, ~prot)) > + ret = EPERM; > + goto unlock; > + > +map_shared: > + /* > + * If the page is not yet shared, adjust mappings in both page-tables > + * while both locks are held. > + */ > + prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED); > + ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot); > + BUG_ON(ret); > + > + prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED); > + ret = host_stage2_idmap_locked(addr, PAGE_SIZE, prot); > + BUG_ON(ret); > + > +unlock: > + hyp_spin_unlock(&pkvm_pgd_lock); > + hyp_spin_unlock(&host_kvm.lock); > + > + return ret; > +} > + > void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) > { > struct kvm_vcpu_fault_info fault; > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 0625bf2353c2..cbab146cda6a 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size, > { > int err; > > - if (!kvm_host_owns_hyp_mappings()) { > - return kvm_call_hyp_nvhe(__pkvm_create_mappings, > - start, size, phys, prot); > - } > + if (WARN_ON(!kvm_host_owns_hyp_mappings())) > + return -EINVAL; > > mutex_lock(&kvm_hyp_pgd_mutex); > err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot); > @@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr) > } > } > > +static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end) > +{ > + phys_addr_t addr; > + int ret; > + > + for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) { > + ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp, > + __phys_to_pfn(addr)); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > /** > * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode > * @from: The virtual kernel start address of the range > @@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot) > if (is_kernel_in_hyp_mode()) > return 0; > > + if (!kvm_host_owns_hyp_mappings()) { > + if (WARN_ON(prot != PAGE_HYP)) > + return -EPERM; > + return pkvm_share_hyp(kvm_kaddr_to_phys(from), > + kvm_kaddr_to_phys(to)); > + } > + > start = start & PAGE_MASK; > end = PAGE_ALIGN(end); > > -- > 2.32.0.605.g8dce9f2422-goog >