From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 2BC17360EFF; Wed, 15 Jul 2026 14:06:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784124416; cv=none; b=pngupLVWo2Tauycfy6vC29D2uZHt0vKZkLOYcEA7KLsweHEqZOVcqe8dYWobF24qIYAjRaOJKLeHezWAeU73qpF0+lF7Rt3q4BVNg7z9VwE577/Z6EDdMlPh1OLob4wtQcC0E5MPRnttAge0ujMsHTVk3xXpEDpNXRMMYE9BVKo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784124416; c=relaxed/simple; bh=1ZeNg9YTuPw/AmC+GZRY0j4BvPPBnhLsNmw1jbgJg7Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ljw85wJboRFsXupkAfQ9mz8M+cpLl2OhBltrAY2v07g5VsDP4STraXBPwaqjgEr8serOXsFFY4j9VsyWt6fNEk02OeLk+7CfsfcKoFIF5jpfdKhsKgWcJNBK+gcRx7mvTl+MTNgNRMYiwfPFgSvWneXz1WRjzICCYXGDjS18l9E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=qFS5q/GE; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="qFS5q/GE" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ABD0F1477; Wed, 15 Jul 2026 07:06:48 -0700 (PDT) Received: from [10.1.25.27] (e122027.cambridge.arm.com [10.1.25.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 73C703F7B4; Wed, 15 Jul 2026 07:06:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784124412; bh=1ZeNg9YTuPw/AmC+GZRY0j4BvPPBnhLsNmw1jbgJg7Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qFS5q/GEJBFM5qm1yviVBB20cZjHISg0vJ8nxqcQRXasfZg1u3OjdqRliIqw9JYsV LPp+Iy5h4umC2YCdohZ+MSbdfnQEob8eaowep9qLC2vtu6yAHTkZxT7pqmPBouYvn3 5INR4WzBfrCmMJuk21PrysPuWCAIeqSAu0xZ5FdI= Message-ID: Date: Wed, 15 Jul 2026 15:06:43 +0100 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 26/44] arm64: RMI: Allow populating initial contents To: Kohei Enju Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo.Pieralisi2@arm.com References: <20260513131757.116630-1-steven.price@arm.com> <20260513131757.116630-27-steven.price@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 14/07/2026 05:37, Kohei Enju wrote: > On 05/13 14:17, Steven Price wrote: >> The VMM needs to populate the realm with some data before starting (e.g. >> a kernel and initrd). This is measured by the RMM and used as part of >> the attestation later on. >> >> Signed-off-by: Steven Price >> --- >> Changes since v13: >> * Rename realm_create_protected_data_page() to realm_data_map_init(). >> Changes since v12: >> * The ioctl now updates the structure with the amount populated rather >> than returning this through the ioctl return code. >> * Use the new RMM v2.0 range based RMI calls. >> * Adapt to upstream changes in kvm_gmem_populate(). >> Changes since v11: >> * The multiplex CAP is gone and there's a new ioctl which makes use of >> the generic kvm_gmem_populate() functionality. >> Changes since v7: >> * Improve the error codes. >> * Other minor changes from review. >> Changes since v6: >> * Handle host potentially having a larger page size than the RMM >> granule. >> * Drop historic "par" (protected address range) from >> populate_par_region() - it doesn't exist within the current >> architecture. >> * Add a cond_resched() call in kvm_populate_realm(). >> Changes since v5: >> * Refactor to use PFNs rather than tracking struct page in >> realm_create_protected_data_page(). >> * Pull changes from a later patch (in the v5 series) for accessing >> pages from a guest memfd. >> * Do the populate in chunks to avoid holding locks for too long and >> triggering RCU stall warnings. >> --- >> arch/arm64/include/asm/kvm_rmi.h | 4 ++ >> arch/arm64/kvm/Kconfig | 1 + >> arch/arm64/kvm/arm.c | 13 ++++ >> arch/arm64/kvm/rmi.c | 106 +++++++++++++++++++++++++++++++ >> 4 files changed, 124 insertions(+) >> >> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h >> index 007249a13dbc..a2b6bc412a22 100644 >> --- a/arch/arm64/include/asm/kvm_rmi.h >> +++ b/arch/arm64/include/asm/kvm_rmi.h >> @@ -88,6 +88,10 @@ int kvm_rec_enter(struct kvm_vcpu *vcpu); >> int kvm_rec_pre_enter(struct kvm_vcpu *vcpu); >> int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_status); >> >> +struct kvm_arm_rmi_populate; >> + >> +int kvm_arm_rmi_populate(struct kvm *kvm, >> + struct kvm_arm_rmi_populate *arg); >> void kvm_realm_unmap_range(struct kvm *kvm, >> unsigned long ipa, >> unsigned long size, >> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig >> index 4e16719fda22..d0cd011cf672 100644 >> --- a/arch/arm64/kvm/Kconfig >> +++ b/arch/arm64/kvm/Kconfig >> @@ -38,6 +38,7 @@ menuconfig KVM >> select GUEST_PERF_EVENTS if PERF_EVENTS >> select KVM_GUEST_MEMFD >> select KVM_GENERIC_MEMORY_ATTRIBUTES >> + select HAVE_KVM_ARCH_GMEM_POPULATE >> help >> Support hosting virtualized guest machines. >> >> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c >> index ed88a203b892..073ba9181da9 100644 >> --- a/arch/arm64/kvm/arm.c >> +++ b/arch/arm64/kvm/arm.c >> @@ -2131,6 +2131,19 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) >> return -EFAULT; >> return kvm_vm_ioctl_get_reg_writable_masks(kvm, &range); >> } >> + case KVM_ARM_RMI_POPULATE: { >> + struct kvm_arm_rmi_populate req; >> + int ret; >> + >> + if (!kvm_is_realm(kvm)) >> + return -ENXIO; >> + if (copy_from_user(&req, argp, sizeof(req))) >> + return -EFAULT; >> + ret = kvm_arm_rmi_populate(kvm, &req); >> + if (copy_to_user(argp, &req, sizeof(req))) >> + return -EFAULT; >> + return ret; >> + } >> default: >> return -EINVAL; >> } >> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c >> index a89873a5eb77..209087bcf399 100644 >> --- a/arch/arm64/kvm/rmi.c >> +++ b/arch/arm64/kvm/rmi.c >> @@ -486,6 +486,75 @@ void kvm_realm_unmap_range(struct kvm *kvm, unsigned long start, >> realm_unmap_private_range(kvm, start, end, may_block); >> } >> >> +static int realm_data_map_init(struct kvm *kvm, unsigned long ipa, >> + kvm_pfn_t dst_pfn, kvm_pfn_t src_pfn, >> + unsigned long flags) >> +{ >> + struct realm *realm = &kvm->arch.realm; >> + phys_addr_t rd = virt_to_phys(realm->rd); >> + phys_addr_t dst_phys, src_phys; >> + int ret; >> + >> + dst_phys = __pfn_to_phys(dst_pfn); >> + src_phys = __pfn_to_phys(src_pfn); >> + >> + if (rmi_delegate_page(dst_phys)) >> + return -ENXIO; >> + >> + ret = rmi_rtt_data_map_init(rd, dst_phys, ipa, src_phys, flags); >> + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) { >> + /* Create missing RTTs and retry */ >> + int level = RMI_RETURN_INDEX(ret); >> + >> + KVM_BUG_ON(level == KVM_PGTABLE_LAST_LEVEL, kvm); >> + >> + ret = realm_create_rtt_levels(realm, ipa, level, >> + KVM_PGTABLE_LAST_LEVEL, NULL); >> + if (!ret) { >> + ret = rmi_rtt_data_map_init(rd, dst_phys, ipa, src_phys, >> + flags); > > I think rmi_rtt_data_map_init() returns a raw RMI return value which is > positive on failure. Shouldn't it be converted to -ENXIO or another > Linux errno before returning it? > > Otherwise, the positive error value can propagate through > kvm_gmem_populate() and populate_region() to kvm_arm_rmi_populate(). > There, it would be treated as the number of pages populated, even though > the operation did not populate any pages. Good spot. >> + } >> + } >> + >> + if (ret) { >> + if (WARN_ON(rmi_undelegate_page(dst_phys))) { >> + /* Undelegate failed, so we leak the page */ >> + get_page(pfn_to_page(dst_pfn)); > > Since realm_create_rtt_levels() returns either 0 or a negative errno, > how about preserving that error and converting any raw RMI erorr to > -ENXIO here? > > return ret < 0 ? ret : -ENXIO; Makes sense, although this needs to be: return ret <= 0 ? ret : -ENXIO; to handle the ret==0 case. I'll fix this in my next posting. >> + } >> + } >> + >> + return ret; >> +} >> + >> +static int populate_region_cb(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, >> + struct page *src_page, void *opaque) >> +{ >> + unsigned long data_flags = *(unsigned long *)opaque; >> + phys_addr_t ipa = gfn_to_gpa(gfn); >> + >> + if (!src_page) >> + return -EOPNOTSUPP; >> + >> + return realm_data_map_init(kvm, ipa, pfn, page_to_pfn(src_page), >> + data_flags); >> +} >> + >> +static long populate_region(struct kvm *kvm, >> + gfn_t base_gfn, >> + unsigned long pages, >> + u64 uaddr, >> + unsigned long data_flags) >> +{ >> + long ret = 0; >> + >> + mutex_lock(&kvm->slots_lock); >> + ret = kvm_gmem_populate(kvm, base_gfn, u64_to_user_ptr(uaddr), pages, >> + populate_region_cb, &data_flags); >> + mutex_unlock(&kvm->slots_lock); >> + >> + return ret; >> +} >> + >> enum ripas_action { >> RIPAS_INIT, >> RIPAS_SET, >> @@ -574,6 +643,43 @@ static int realm_ensure_created(struct kvm *kvm) >> return -ENXIO; >> } >> >> +int kvm_arm_rmi_populate(struct kvm *kvm, >> + struct kvm_arm_rmi_populate *args) >> +{ >> + unsigned long data_flags = 0; >> + unsigned long ipa_start = args->base; >> + unsigned long ipa_end = ipa_start + args->size; >> + long pages_populated; >> + int ret; >> + >> + if (args->reserved || >> + (args->flags & ~KVM_ARM_RMI_POPULATE_FLAGS_MEASURE) || >> + !IS_ALIGNED(ipa_start, PAGE_SIZE) || >> + !IS_ALIGNED(ipa_end, PAGE_SIZE) || >> + !IS_ALIGNED(args->source_uaddr, PAGE_SIZE)) >> + return -EINVAL; >> + >> + ret = realm_ensure_created(kvm); >> + if (ret) >> + return ret; > > If I understand correctly, concurrent KVM_ARM_RMI_POPULATE calls can > race with each other in realm_ensure_created(). > > realm_ensure_created() calls realm_create_rd() when kvm_realm_state() == > REALM_STATE_NONE. Since kvm->arch.config_lock is not held here, multiple > threads could enter realm_create_rd() concurrently. > > KVM_ARM_RMI_POPULATE can also race with KVM_RUN through > kvm_activate_realm(). kvm_activate_realm() takes kvm->arch.config_lock > while checking the Realm state, calling realm_ensure_created(), and > updating the state, whereas KVM_ARM_RMI_POPULATE does not. > > How about serializing Realm creation here as follows? > scoped_guard(mutex, &kvm->arch.config_lock) { > ret = realm_ensure_created(kvm); > if (ret) > return ret; > } > > Does that make sense? Yes this is a bug I'd already caught and is due to the fixed in my next posting - similar to what you suggest the config_lock is now held when realm_ensure_created() is called (and I've put a lockdep_assert_held() in realm_ensure_created). Thanks, Steve >> + >> + if (args->flags & KVM_ARM_RMI_POPULATE_FLAGS_MEASURE) >> + data_flags |= RMI_MEASURE_CONTENT; >> + >> + pages_populated = populate_region(kvm, gpa_to_gfn(ipa_start), >> + args->size >> PAGE_SHIFT, >> + args->source_uaddr, data_flags); >> + >> + if (pages_populated < 0) >> + return pages_populated; >> + >> + args->size -= pages_populated << PAGE_SHIFT; >> + args->source_uaddr += pages_populated << PAGE_SHIFT; >> + args->base += pages_populated << PAGE_SHIFT; >> + >> + return 0; >> +} >> + >> static void kvm_complete_ripas_change(struct kvm_vcpu *vcpu) >> { >> struct kvm *kvm = vcpu->kvm; >> -- >> 2.43.0 >> >>