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 DE7942B9BF; Thu, 1 May 2025 15:09:27 +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=1746112170; cv=none; b=aC/max5uv8cNUPcvO2AbWdffxr3bj3gVJeMWv6bljT9LY/8uCiT9708BfwD5qppUkvj4nMs3FyNINYj9NfwHP79ZZHHUkZzftQ6RHlmUlcG1WaBhW+1mfWuYSb81810Pcn61KfB/7OIt77dVGmxlOQy+IXZkLyep38Kh16RQvJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746112170; c=relaxed/simple; bh=qbY0qOFUzw+PTnrPzmFEZi/Qq4LnrpAgxilwf1yXdeA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fZAFqCWFCV35sdqyONS4kzOeMuQQTG82On8BZUbyrEClLgoqRPVmEunNNnhXmkL+IlzXax63z5lUWd0pdZKqd5MEXzba1yvKaPMyj1XBSdad5J0kIGF2WruKAc38WW26d3NXONleqkANbRw6/7wI1wA2ndHaj9BBuXGFw6lEg9Y= 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; 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 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 E671E168F; Thu, 1 May 2025 08:09:13 -0700 (PDT) Received: from [10.1.33.27] (e122027.cambridge.arm.com [10.1.33.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0D8153F5A1; Thu, 1 May 2025 08:09:17 -0700 (PDT) Message-ID: Date: Thu, 1 May 2025 16:09:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 07/43] arm64: RME: ioctls to create and configure realms To: Suzuki K Poulose , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , 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" References: <20250416134208.383984-1-steven.price@arm.com> <20250416134208.383984-8-steven.price@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 29/04/2025 10:45, Suzuki K Poulose wrote: > On 16/04/2025 14:41, Steven Price wrote: >> Add the KVM_CAP_ARM_RME_CREATE_RD ioctl to create a realm. This involves >> delegating pages to the RMM to hold the Realm Descriptor (RD) and for >> the base level of the Realm Translation Tables (RTT). A VMID also need >> to be picked, since the RMM has a separate VMID address space a >> dedicated allocator is added for this purpose. >> >> KVM_CAP_ARM_RME_CONFIG_REALM is provided to allow configuring the realm >> before it is created. Configuration options can be classified as: >> >>   1. Parameters specific to the Realm stage2 (e.g. IPA Size, vmid, stage2 >>      entry level, entry level RTTs, number of RTTs in start level, LPA2) >>      Most of these are not measured by RMM and comes from KVM book >>      keeping. >> >>   2. Parameters controlling "Arm Architecture features for the VM". (e.g. >>      SVE VL, PMU counters, number of HW BRPs/WPs), configured by the VMM >>      using the "user ID register write" mechanism. These will be >>      supported in the later patches. >> >>   3. Parameters are not part of the core Arm architecture but defined >>      by the RMM spec (e.g. Hash algorithm for measurement, >>      Personalisation value). These are programmed via >>      KVM_CAP_ARM_RME_CONFIG_REALM. >> >> For the IPA size there is the possibility that the RMM supports a >> different size to the IPA size supported by KVM for normal guests. At >> the moment the 'normal limit' is exposed by KVM_CAP_ARM_VM_IPA_SIZE and >> the IPA size is configured by the bottom bits of vm_type in >> KVM_CREATE_VM. This means that it isn't easy for the VMM to discover >> what IPA sizes are supported for Realm guests. Since the IPA is part of >> the measurement of the realm guest the current expectation is that the >> VMM will be required to pick the IPA size demanded by attestation and >> therefore simply failing if this isn't available is fine. An option >> would be to expose a new capability ioctl to obtain the RMM's maximum >> IPA size if this is needed in the future. >> >> Co-developed-by: Suzuki K Poulose >> Signed-off-by: Suzuki K Poulose >> Signed-off-by: Steven Price >> Reviewed-by: Gavin Shan >> --- >> Changes since v7: >>   * Minor code cleanup following Gavin's review. >> Changes since v6: >>   * Separate RMM RTT calculations from host PAGE_SIZE. This allows the >>     host page size to be larger than 4k while still communicating with an >>     RMM which uses 4k granules. >> Changes since v5: >>   * Introduce free_delegated_granule() to replace many >>     undelegate/free_page() instances and centralise the comment on >>     leaking when the undelegate fails. >>   * Several other minor improvements suggested by reviews - thanks for >>     the feedback! >> Changes since v2: >>   * Improved commit description. >>   * Improved return failures for rmi_check_version(). >>   * Clear contents of PGD after it has been undelegated in case the RMM >>     left stale data. >>   * Minor changes to reflect changes in previous patches. >> --- >>   arch/arm64/include/asm/kvm_emulate.h |   5 + >>   arch/arm64/include/asm/kvm_rme.h     |  19 ++ >>   arch/arm64/kvm/arm.c                 |  16 ++ >>   arch/arm64/kvm/mmu.c                 |  22 +- >>   arch/arm64/kvm/rme.c                 | 319 +++++++++++++++++++++++++++ >>   5 files changed, 379 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/ >> include/asm/kvm_emulate.h >> index 1c43a4fc25dd..4ee6c215da82 100644 >> --- a/arch/arm64/include/asm/kvm_emulate.h >> +++ b/arch/arm64/include/asm/kvm_emulate.h >> @@ -699,6 +699,11 @@ static inline enum realm_state >> kvm_realm_state(struct kvm *kvm) >>       return READ_ONCE(kvm->arch.realm.state); >>   } >>   +static inline bool kvm_realm_is_created(struct kvm *kvm) >> +{ >> +    return kvm_is_realm(kvm) && kvm_realm_state(kvm) != >> REALM_STATE_NONE; >> +} >> + >>   static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu) >>   { >>       return false; >> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/ >> asm/kvm_rme.h >> index 9c8a0b23e0e4..5dc1915de891 100644 >> --- a/arch/arm64/include/asm/kvm_rme.h >> +++ b/arch/arm64/include/asm/kvm_rme.h >> @@ -6,6 +6,8 @@ >>   #ifndef __ASM_KVM_RME_H >>   #define __ASM_KVM_RME_H >>   +#include >> + >>   /** >>    * enum realm_state - State of a Realm >>    */ >> @@ -46,11 +48,28 @@ enum realm_state { >>    * struct realm - Additional per VM data for a Realm >>    * >>    * @state: The lifetime state machine for the realm >> + * @rd: Kernel mapping of the Realm Descriptor (RD) >> + * @params: Parameters for the RMI_REALM_CREATE command >> + * @num_aux: The number of auxiliary pages required by the RMM >> + * @vmid: VMID to be used by the RMM for the realm >> + * @ia_bits: Number of valid Input Address bits in the IPA >>    */ >>   struct realm { >>       enum realm_state state; >> + >> +    void *rd; >> +    struct realm_params *params; >> + >> +    unsigned long num_aux; >> +    unsigned int vmid; >> +    unsigned int ia_bits; >>   }; >>     void kvm_init_rme(void); >> +u32 kvm_realm_ipa_limit(void); >> + >> +int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap); >> +int kvm_init_realm_vm(struct kvm *kvm); >> +void kvm_destroy_realm(struct kvm *kvm); >>     #endif /* __ASM_KVM_RME_H */ >> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c >> index 856a721d41ac..0e8482fdc4d3 100644 >> --- a/arch/arm64/kvm/arm.c >> +++ b/arch/arm64/kvm/arm.c >> @@ -136,6 +136,11 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, >>           } >>           mutex_unlock(&kvm->lock); >>           break; >> +    case KVM_CAP_ARM_RME: >> +        mutex_lock(&kvm->lock); >> +        r = kvm_realm_enable_cap(kvm, cap); >> +        mutex_unlock(&kvm->lock); >> +        break; >>       default: >>           break; >>       } >> @@ -198,6 +203,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned >> long type) >>         bitmap_zero(kvm->arch.vcpu_features, KVM_VCPU_MAX_FEATURES); >>   +    /* Initialise the realm bits after the generic bits are enabled */ >> +    if (kvm_is_realm(kvm)) { >> +        ret = kvm_init_realm_vm(kvm); >> +        if (ret) >> +            goto err_free_cpumask; >> +    } >> + >>       return 0; >>     err_free_cpumask: >> @@ -257,6 +269,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm) >>       kvm_unshare_hyp(kvm, kvm + 1); >>         kvm_arm_teardown_hypercalls(kvm); >> +    kvm_destroy_realm(kvm); >>   } >>     static bool kvm_has_full_ptr_auth(void) >> @@ -405,6 +418,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, >> long ext) >>       case KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES: >>           r = BIT(0); >>           break; >> +    case KVM_CAP_ARM_RME: >> +        r = static_key_enabled(&kvm_rme_is_available); >> +        break; >>       default: >>           r = 0; >>       } >> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c >> index 2feb6c6b63af..5957a07de86d 100644 >> --- a/arch/arm64/kvm/mmu.c >> +++ b/arch/arm64/kvm/mmu.c >> @@ -876,12 +876,16 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = { >>       .icache_inval_pou    = invalidate_icache_guest_page, >>   }; >>   -static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long >> type) >> +static int kvm_init_ipa_range(struct kvm *kvm, >> +                  struct kvm_s2_mmu *mmu, unsigned long type) >>   { >>       u32 kvm_ipa_limit = get_kvm_ipa_limit(); >>       u64 mmfr0, mmfr1; >>       u32 phys_shift; >>   +    if (kvm_is_realm(kvm)) >> +        kvm_ipa_limit = kvm_realm_ipa_limit(); >> + >>       if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK) >>           return -EINVAL; >>   @@ -946,7 +950,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct >> kvm_s2_mmu *mmu, unsigned long t >>           return -EINVAL; >>       } >>   -    err = kvm_init_ipa_range(mmu, type); >> +    err = kvm_init_ipa_range(kvm, mmu, type); >>       if (err) >>           return err; >>   @@ -1072,6 +1076,20 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu) >>       struct kvm_pgtable *pgt = NULL; >>         write_lock(&kvm->mmu_lock); >> +    if (kvm_is_realm(kvm) && >> +        (kvm_realm_state(kvm) != REALM_STATE_DEAD && >> +         kvm_realm_state(kvm) != REALM_STATE_NONE)) { >> +        /* Tearing down RTTs will be added in a later patch */ >> +        write_unlock(&kvm->mmu_lock); >> + >> +        /* >> +         * The physical PGD pages are delegated to the RMM, so cannot >> +         * be freed at this point. This function will be called again >> +         * from kvm_destroy_realm() after the physical pages have been >> +         * returned at which point the memory can be freed. >> +         */ >> +        return; >> +    } >>       pgt = mmu->pgt; >>       if (pgt) { >>           mmu->pgd_phys = 0; >> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c >> index 67cf2d94cb2d..dbb6521fe380 100644 >> --- a/arch/arm64/kvm/rme.c >> +++ b/arch/arm64/kvm/rme.c >> @@ -5,9 +5,23 @@ >>     #include >>   +#include >> +#include >>   #include >>   #include >>   +#include >> + >> +static unsigned long rmm_feat_reg0; >> + >> +#define RMM_PAGE_SHIFT        12 >> +#define RMM_PAGE_SIZE        BIT(RMM_PAGE_SHIFT) >> + >> +static bool rme_has_feature(unsigned long feature) >> +{ >> +    return !!u64_get_bits(rmm_feat_reg0, feature); >> +} >> + >>   static int rmi_check_version(void) >>   { >>       struct arm_smccc_res res; >> @@ -42,6 +56,305 @@ static int rmi_check_version(void) >>       return 0; >>   } >>   +u32 kvm_realm_ipa_limit(void) >> +{ >> +    return u64_get_bits(rmm_feat_reg0, RMI_FEATURE_REGISTER_0_S2SZ); >> +} >> + >> +static int get_start_level(struct realm *realm) >> +{ >> +    return 4 - ((realm->ia_bits - 8) / (RMM_PAGE_SHIFT - 3)); > > minor nit: It may be worth adding a comment here, how we got this magic > number 8. We could say: > > Open coded version of ARM64_HW_PGTABLE_LEVELS(ia_bits - 4) (accounting > for the concatenation of upto 16 tables in entry level) for RMM Stage2. > Agreed a comment makes sense. This is actually an open coded version of "4 - stage2_pgtable_levels()" but using the RMM's page size (indeed previous versions of the series did exactly that). There's already a comment for stage2_pgtable_levels() explaining the concatenation. >> +} >> + >> +static void free_delegated_granule(phys_addr_t phys) >> +{ >> +    if (WARN_ON(rmi_granule_undelegate(phys))) { >> +        /* Undelegate failed: leak the page */ >> +        return; >> +    } >> + >> +    kvm_account_pgtable_pages(phys_to_virt(phys), -1); >> + >> +    free_page((unsigned long)phys_to_virt(phys)); >> +} >> + >> +/* Calculate the number of s2 root rtts needed */ >> +static int realm_num_root_rtts(struct realm *realm) >> +{ >> +    unsigned int ipa_bits = realm->ia_bits; >> +    unsigned int levels = 3 - get_start_level(realm); > > nit: Why is this 3 - start_level and not 4 ? Though that is compensated > by the "levels + 1" below, hence the calculation is correct. I honestly can't remember - will change ;) >> +    unsigned int sl_ipa_bits = (levels + 1) * (RMM_PAGE_SHIFT - 3) + >> +                   RMM_PAGE_SHIFT; >> + >> +    if (sl_ipa_bits >= ipa_bits) >> +        return 1; >> + >> +    return 1 << (ipa_bits - sl_ipa_bits); >> +} >> + >> +static int realm_create_rd(struct kvm *kvm) >> +{ >> +    struct realm *realm = &kvm->arch.realm; >> +    struct realm_params *params = realm->params; >> +    void *rd = NULL; >> +    phys_addr_t rd_phys, params_phys; >> +    size_t pgd_size = kvm_pgtable_stage2_pgd_size(kvm->arch.mmu.vtcr); >> +    int i, r; >> +    int rtt_num_start; >> + >> +    realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr); >> +    rtt_num_start = realm_num_root_rtts(realm); >> + >> +    if (WARN_ON(realm->rd || !realm->params)) >> +        return -EEXIST; >> + >> +    if (pgd_size / RMM_PAGE_SIZE < rtt_num_start) >> +        return -EINVAL; >> + >> +    rd = (void *)__get_free_page(GFP_KERNEL); >> +    if (!rd) >> +        return -ENOMEM; >> + >> +    rd_phys = virt_to_phys(rd); >> +    if (rmi_granule_delegate(rd_phys)) { >> +        r = -ENXIO; >> +        goto free_rd; >> +    } >> + >> +    for (i = 0; i < pgd_size; i += RMM_PAGE_SIZE) { >> +        phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i; >> + >> +        if (rmi_granule_delegate(pgd_phys)) { >> +            r = -ENXIO; >> +            goto out_undelegate_tables; >> +        } >> +    } >> + >> +    params->s2sz = VTCR_EL2_IPA(kvm->arch.mmu.vtcr); >> +    params->rtt_level_start = get_start_level(realm); >> +    params->rtt_num_start = rtt_num_start; >> +    params->rtt_base = kvm->arch.mmu.pgd_phys; >> +    params->vmid = realm->vmid; >> + >> +    params_phys = virt_to_phys(params); >> + >> +    if (rmi_realm_create(rd_phys, params_phys)) { >> +        r = -ENXIO; >> +        goto out_undelegate_tables; >> +    } >> + >> +    if (WARN_ON(rmi_rec_aux_count(rd_phys, &realm->num_aux))) { >> +        WARN_ON(rmi_realm_destroy(rd_phys)); >> +        goto out_undelegate_tables; >> +    } >> + >> +    realm->rd = rd; >> + >> +    return 0; >> + >> +out_undelegate_tables: >> +    while (i > 0) { >> +        i -= RMM_PAGE_SIZE; >> + >> +        phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i; >> + >> +        if (WARN_ON(rmi_granule_undelegate(pgd_phys))) { >> +            /* Leak the pages if they cannot be returned */ >> +            kvm->arch.mmu.pgt = NULL; >> +            break; >> +        } > > minor nit: Do we need to try undelegating the other pages ? We could > make that WARN_ON_ONCE() too. We could do, but there's no real point unless we also deal with leaking only the pages which cannot be undelegated. Considering this is a "should never happen" case I felt it was better to keep the code simple and leak more than necessary. To me this feels like a "save everything and reboot as soon as possible" sort of error condition - the kernel (or RMM) has lost track of which pages are delegated and so a GPT fault could be coming at any point. So it's better to play safe and be pessimistic. Thanks, Steve