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Tue, 01 Sep 2026 03:09:30 -0700 (PDT) Received: from lleonard-thinkpadx1carbongen13.rmtit.csb ([151.29.41.106]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48442d7c1c0sm3941620f8f.32.2026.09.01.03.09.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 03:09:29 -0700 (PDT) From: Luigi Leonardi Date: Tue, 01 Sep 2026 12:09:18 +0200 Subject: [PATCH 1/4] sev: rename set_guest_policy to set_id_block and remove dead policy code Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260901-fix_igvm_policy-v1-1-e93a6cf8c5ac@redhat.com> References: <20260901-fix_igvm_policy-v1-0-e93a6cf8c5ac@redhat.com> In-Reply-To: <20260901-fix_igvm_policy-v1-0-e93a6cf8c5ac@redhat.com> To: qemu-devel@nongnu.org Cc: Gerd Hoffmann , Stefano Garzarella , Ani Sinha , Paolo Bonzini , Zhao Liu , Marcelo Tosatti , kvm@vger.kernel.org, Luigi Leonardi X-Mailer: b4 0.14.3 The guest policy must be provided at guest launch start: LAUNCH_START for SEV/SEV-ES and SNP_LAUNCH_START for SEV-SNP. See the SEV API specification, chapter 3 (Guest Policy), and the SEV-SNP firmware ABI specification, section 4.3 (Guest Policy). The policy parameter in set_guest_policy was never effective: by the time this callback runs, LAUNCH_START has already been issued for both SEV/SEV-ES and SEV-SNP, so writing to kvm_start_conf.policy or sev_guest->policy has no effect. In practice the only thing this callback actually does is set the ID block and ID auth for SNP's LAUNCH_FINISH, so rename it to set_id_block to reflect its real purpose, remove the unused policy parameter, and drop the non-SNP code path which was entirely dead. This is preliminary work: actually forwarding the guest policy to the platform before LAUNCH_START is added in a later commit. Signed-off-by: Luigi Leonardi --- backends/confidential-guest-support.c | 12 ++- backends/igvm.c | 6 +- include/system/confidential-guest-support.h | 28 ++++--- target/i386/sev.c | 118 +++++++++++----------------- 4 files changed, 67 insertions(+), 97 deletions(-) diff --git a/backends/confidential-guest-support.c b/backends/confidential-guest-support.c index 156dd15e66..a0b36d2da5 100644 --- a/backends/confidential-guest-support.c +++ b/backends/confidential-guest-support.c @@ -38,14 +38,12 @@ static int set_guest_state(hwaddr gpa, uint8_t *ptr, uint64_t len, return -1; } -static int set_guest_policy(ConfidentialGuestPolicyType policy_type, - uint64_t policy, - void *policy_data1, uint32_t policy_data1_size, - void *policy_data2, uint32_t policy_data2_size, - Error **errp) +static int set_id_block(void *id_block, uint32_t id_block_size, + void *id_auth, uint32_t id_auth_size, + Error **errp) { error_setg(errp, - "Setting confidential guest policy is not supported for this platform"); + "Setting ID block is not supported for this platform"); return -1; } @@ -64,7 +62,7 @@ static void confidential_guest_support_class_init(ObjectClass *oc, ConfidentialGuestSupportClass *cgsc = CONFIDENTIAL_GUEST_SUPPORT_CLASS(oc); cgsc->check_support = check_support; cgsc->set_guest_state = set_guest_state; - cgsc->set_guest_policy = set_guest_policy; + cgsc->set_id_block = set_id_block; cgsc->get_mem_map_entry = get_mem_map_entry; } diff --git a/backends/igvm.c b/backends/igvm.c index 7b7bdc72b7..85de0d54ec 100644 --- a/backends/igvm.c +++ b/backends/igvm.c @@ -968,9 +968,9 @@ static int qigvm_handle_policy(QIgvm *ctx, Error **errp) id_block_len = sizeof(struct sev_id_block); id_auth_len = sizeof(struct sev_id_authentication); } - return ctx->cgsc->set_guest_policy(GUEST_POLICY_SEV, ctx->sev_policy, - ctx->id_block, id_block_len, - ctx->id_auth, id_auth_len, errp); + + return ctx->cgsc->set_id_block(ctx->id_block, id_block_len, + ctx->id_auth, id_auth_len, errp); } return 0; } diff --git a/include/system/confidential-guest-support.h b/include/system/confidential-guest-support.h index 5dca717308..6d35ddb97a 100644 --- a/include/system/confidential-guest-support.h +++ b/include/system/confidential-guest-support.h @@ -128,21 +128,23 @@ typedef struct ConfidentialGuestSupportClass { uint16_t cpu_index, Error **errp); /* - * Set the guest policy. The policy can be used to configure the - * confidential platform, such as if debug is enabled or not and can contain - * information about expected launch measurements, signed verification of - * guest configuration and other platform data. - * - * The format of the policy data is specific to each platform. For example, - * SEV-SNP uses a policy bitfield in the 'policy' argument and provides an - * ID block and ID authentication in the 'policy_data' parameters. The type - * of policy data is identified by the 'policy_type' argument. + * Set the guest policy for the confidential platform. The policy + * configures properties of the guest, such as whether debug is + * enabled. Its format is platform-specific; for SEV/SEV-ES and + * SEV-SNP it is a policy bitfield. Must be called before LAUNCH_START + * so the policy is in effect for launch. */ int (*set_guest_policy)(ConfidentialGuestPolicyType policy_type, - uint64_t policy, - void *policy_data1, uint32_t policy_data1_size, - void *policy_data2, uint32_t policy_data2_size, - Error **errp); + uint64_t policy, Error **errp); + + /* + * Set the SEV-SNP ID block and ID authentication block. These are + * passed to SNP_LAUNCH_FINISH to provide signed verification of the + * guest configuration. + */ + int (*set_id_block)(void *id_block, uint32_t id_block_size, + void *id_auth, uint32_t id_auth_size, + Error **errp); /* * Iterate the system memory map, getting the entry with the given index diff --git a/target/i386/sev.c b/target/i386/sev.c index 4d875d10ff..465415c535 100644 --- a/target/i386/sev.c +++ b/target/i386/sev.c @@ -2723,10 +2723,9 @@ static int cgs_get_mem_map_entry(int index, return 0; } -static int cgs_set_guest_policy(ConfidentialGuestPolicyType policy_type, - uint64_t policy, void *policy_data1, - uint32_t policy_data1_size, void *policy_data2, - uint32_t policy_data2_size, Error **errp) +static int cgs_set_id_block(void *id_block, uint32_t id_block_size, + void *id_auth, uint32_t id_auth_size, + Error **errp) { SevCommonState *sev_common = SEV_COMMON(MACHINE(qdev_get_machine())->cgs); if (sev_common->state == SEV_STATE_UNINIT) { @@ -2734,86 +2733,57 @@ static int cgs_set_guest_policy(ConfidentialGuestPolicyType policy_type, return 0; } - if (policy_type != GUEST_POLICY_SEV) { - error_setg(errp, "SEV: Invalid guest policy type provided for SEV: %d", - policy_type); + if (!sev_snp_enabled()) { + error_setg(errp, "SEV: ID block is only supported for SEV-SNP"); return -1; } - /* - * SEV-SNP handles policy differently. The policy flags are defined in - * kvm_start_conf.policy and an ID block and ID auth can be provided. - */ - if (sev_snp_enabled()) { - SevSnpGuestState *sev_snp_guest = - SEV_SNP_GUEST(MACHINE(qdev_get_machine())->cgs); - struct kvm_sev_snp_launch_finish *finish = - &sev_snp_guest->kvm_finish_conf; - /* - * The policy consists of flags in 'policy' and optionally an ID block - * and ID auth in policy_data1 and policy_data2 respectively. The ID - * block and auth are optional so clear any previous ID block and auth - * and set them if provided, but always set the policy flags. - */ - g_free(sev_snp_guest->id_block); - g_free((guchar *)finish->id_block_uaddr); - g_free(sev_snp_guest->id_auth); - g_free((guchar *)finish->id_auth_uaddr); - sev_snp_guest->id_block = NULL; - finish->id_block_uaddr = 0; - sev_snp_guest->id_auth = NULL; - finish->id_auth_uaddr = 0; - - if (policy_data1_size > 0) { - struct sev_snp_id_authentication *id_auth = - (struct sev_snp_id_authentication *)policy_data2; - - if (policy_data1_size != KVM_SEV_SNP_ID_BLOCK_SIZE) { - error_setg(errp, "SEV: Invalid SEV-SNP ID block: incorrect size"); - return -1; - } - if (policy_data2_size != KVM_SEV_SNP_ID_AUTH_SIZE) { - error_setg(errp, - "SEV: Invalid SEV-SNP ID auth block: incorrect size"); - return -1; - } - assert(policy_data1 != NULL); - assert(policy_data2 != NULL); + SevSnpGuestState *sev_snp_guest = + SEV_SNP_GUEST(MACHINE(qdev_get_machine())->cgs); + struct kvm_sev_snp_launch_finish *finish = + &sev_snp_guest->kvm_finish_conf; - finish->id_block_uaddr = - (__u64)g_memdup2(policy_data1, KVM_SEV_SNP_ID_BLOCK_SIZE); - finish->id_auth_uaddr = - (__u64)g_memdup2(policy_data2, KVM_SEV_SNP_ID_AUTH_SIZE); + g_free(sev_snp_guest->id_block); + g_free((guchar *)finish->id_block_uaddr); + g_free(sev_snp_guest->id_auth); + g_free((guchar *)finish->id_auth_uaddr); + sev_snp_guest->id_block = NULL; + finish->id_block_uaddr = 0; + sev_snp_guest->id_auth = NULL; + finish->id_auth_uaddr = 0; - /* - * Check if an author key has been provided and use that to flag - * whether the author key is enabled. The first of the author key - * must be non-zero to indicate the key type, which will currently - * always be 2. - */ - sev_snp_guest->kvm_finish_conf.auth_key_en = - id_auth->author_key[0] ? 1 : 0; - finish->id_block_en = 1; - } + if (id_block_size > 0) { + struct sev_snp_id_authentication *auth = + (struct sev_snp_id_authentication *)id_auth; - /* do not reset existing policy if policy was not set in IGVM */ - if (policy != 0) { - sev_snp_guest->kvm_start_conf.policy = policy; + if (id_block_size != KVM_SEV_SNP_ID_BLOCK_SIZE) { + error_setg(errp, "SEV: Invalid SEV-SNP ID block: incorrect size"); + return -1; } - } else { - SevGuestState *sev_guest = SEV_GUEST(MACHINE(qdev_get_machine())->cgs); - /* Only the policy flags are supported for SEV and SEV-ES */ - if ((policy_data1_size > 0) || (policy_data2_size > 0) || !sev_guest) { - error_setg(errp, "SEV: An ID block/ID auth block has been provided " - "but SEV-SNP is not enabled"); + if (id_auth_size != KVM_SEV_SNP_ID_AUTH_SIZE) { + error_setg(errp, + "SEV: Invalid SEV-SNP ID auth block: incorrect size"); return -1; } + assert(id_block != NULL); + assert(id_auth != NULL); - /* do not reset existing policy if policy was not set in IGVM */ - if (policy != 0) { - sev_guest->policy = policy; - } + finish->id_block_uaddr = + (__u64)g_memdup2(id_block, KVM_SEV_SNP_ID_BLOCK_SIZE); + finish->id_auth_uaddr = + (__u64)g_memdup2(id_auth, KVM_SEV_SNP_ID_AUTH_SIZE); + + /* + * Check if an author key has been provided and use that to flag + * whether the author key is enabled. The first of the author key + * must be non-zero to indicate the key type, which will currently + * always be 2. + */ + sev_snp_guest->kvm_finish_conf.auth_key_en = + auth->author_key[0] ? 1 : 0; + finish->id_block_en = 1; } + return 0; } @@ -2878,7 +2848,7 @@ sev_common_instance_init(Object *obj) cgs->check_support = cgs_check_support; cgs->set_guest_state = cgs_set_guest_state; cgs->get_mem_map_entry = cgs_get_mem_map_entry; - cgs->set_guest_policy = cgs_set_guest_policy; + cgs->set_id_block = cgs_set_id_block; cgs->can_rebuild_guest_state = true; QTAILQ_INIT(&sev_common->launch_vmsa); -- 2.55.0