From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=85.214.250.239 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793619731; b=sqk1Wgv/yLCbL7XpJxW22W6mO7Ej2oNCfUyySm9jwR7vZDc6XrS5+j/hMLbBdAnubEkN 0EUts1yMP0GdvnuxxqWqtSOvJe0ndp7brBaprA2gal6QkEkaQr6mJcjXmb+6p/KGu/oSC 6g4gwqntX5Bdw2yj1Tpk7Nhfh1AnSlXN4tcp3l+oi8xGLvRQ6TaaZJJbaQYX4Hhpa7tfw BZMC0lbqHyUvn3N7U7656KbWO0SeIKoXaql4xdNYcUILMEWqKDhjos1c6506z4QCMwMMO DD66U5RC0RQFB6pM1EEJ8eTsHY91hkXNT7/lsBEe/dCH3JJZZKz0AZXMe9YTrbnRTHg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793619731; h=DMARC-Filter:Received:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=XfqbgcmUIK+2Zk7EPOWKeSkE+vUNrYIyxGFj5yeMr7U=; b=IyR89s0s9zM57uWE5laYEWS4MFR4aJsU8glnro+oTcFE86gxr4TWi3NerdUYxh1EojTT 2p0CVylBZ4/QG2fBD4K3bRR+rUsa34BuQ5IfU3FELFWGSKCwj1uJINB3k7MXzrXHVfYMA OmVolaXJDEl88TJ9iEX7vt3WZXPxe5dNIPeVvhsxSDEPIkE/j+wdJkdgd4wz7cz5ATXFM fssfhrw+aRkEqzMPhFkSc6gtGFeTabpxPbM4UF8qx+xbzdq+VLzVmhTt8vanPSLb51vDX PnzMGmPPQhmuhGMGSSfhPlb1qBE/3nqWpvy2Z+cKDsurcMZa4cAB3hAoZ9wOvKHvl7Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none header.from=8bytes.org; spf=pass smtp.mailfrom=8bytes.org; arc=none smtp.remote-ip=85.214.250.239 Received: from mail.8bytes.org (mail.8bytes.org [85.214.250.239]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C7FC6606A333; Mon, 2 Nov 2026 11:42:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org C7FC6606A333 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=8bytes.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=8bytes.org Received: from io.fritz.box (p200300f6af404a0027ad06761c59e6b3.dip0.t-ipconnect.de [IPv6:2003:f6:af40:4a00:27ad:676:1c59:e6b3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.8bytes.org (Postfix) with ESMTPSA id 357BE243AD2; Mon, 2 Nov 2026 12:42:04 +0100 (CET) From: =?UTF-8?q?J=C3=B6rg=20R=C3=B6del?= To: Paolo Bonzini , Sean Christopherson Cc: Michael Roth , Liam Merwick , Vishal Annapurve , Ninad Naik , Joerg Roedel , Tom Lendacky , James Bottomley , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, coconut-svsm@lists.linux.dev, joro@8bytes.org Subject: [PATCH v3 2/8] KVM: SVM: Implement GET_AP_APIC_IDS NAE event Date: Mon, 2 Nov 2026 12:41:31 +0100 Message-ID: <20261102114137.1198982-3-joro@8bytes.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261102114137.1198982-1-joro@8bytes.org> References: <20261102114137.1198982-1-joro@8bytes.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Joerg Roedel Advertise and handle the GHCB APIC ID list feature so that SNP guests can discover the vCPUs for which they need to create VMSAs without relying on INIT-SIPI. Return the required page count for undersized buffers. For sufficiently large requests, validate the GPA range and use KVM's SRCU-protected guest write path to copy an exact snapshot of the online vCPU APIC IDs. Signed-off-by: Joerg Roedel --- arch/x86/include/asm/sev-common.h | 1 + arch/x86/include/uapi/asm/svm.h | 1 + arch/x86/kvm/svm/sev.c | 67 ++++++++++++++++++++++++++++++- 3 files changed, 67 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h index 01a6e4dbe423..c041f85dfd5c 100644 --- a/arch/x86/include/asm/sev-common.h +++ b/arch/x86/include/asm/sev-common.h @@ -136,6 +136,7 @@ enum psc_op { #define GHCB_HV_FT_SNP BIT_ULL(0) #define GHCB_HV_FT_SNP_AP_CREATION BIT_ULL(1) +#define GHCB_HV_FT_APIC_ID_LIST BIT_ULL(4) #define GHCB_HV_FT_SNP_MULTI_VMPL BIT_ULL(5) /* diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h index e80676185092..c9c85891971a 100644 --- a/arch/x86/include/uapi/asm/svm.h +++ b/arch/x86/include/uapi/asm/svm.h @@ -118,6 +118,7 @@ #define SVM_VMGEXIT_AP_CREATE_ON_INIT 0 #define SVM_VMGEXIT_AP_CREATE 1 #define SVM_VMGEXIT_AP_DESTROY 2 +#define SVM_VMGEXIT_GET_APIC_IDS 0x80000017ull #define SVM_VMGEXIT_SNP_RUN_VMPL 0x80000018ull #define SVM_VMGEXIT_SAVIC 0x8000001aull #define SVM_VMGEXIT_SAVIC_REGISTER_GPA 0 diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index b90c5f14c1ac..f690edaf8b69 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -40,7 +40,9 @@ #define GHCB_VERSION_MAX 2ULL #define GHCB_VERSION_MIN 1ULL -#define GHCB_HV_FT_SUPPORTED (GHCB_HV_FT_SNP | GHCB_HV_FT_SNP_AP_CREATION) +#define GHCB_HV_FT_SUPPORTED (GHCB_HV_FT_SNP | \ + GHCB_HV_FT_SNP_AP_CREATION | \ + GHCB_HV_FT_APIC_ID_LIST) /* * The GHCB spec essentially states that all non-zero error codes other than @@ -3517,7 +3519,8 @@ static bool sev_es_are_required_ghcb_fields_valid(struct vcpu_svm *svm) case SVM_VMGEXIT_AP_CREATION: return kvm_ghcb_rax_is_valid(svm) || lower_32_bits(control->exit_info_1) == SVM_VMGEXIT_AP_DESTROY; - break; + case SVM_VMGEXIT_GET_APIC_IDS: + return kvm_ghcb_rax_is_valid(svm); case SVM_VMGEXIT_MMIO_READ: case SVM_VMGEXIT_MMIO_WRITE: case SVM_VMGEXIT_PSC: @@ -4235,6 +4238,63 @@ static int sev_snp_ap_creation(struct vcpu_svm *svm) return 0; } +struct sev_apic_id_desc { + u32 num_entries; + u32 apic_ids[]; +}; + +static int sev_snp_get_apic_ids(struct vcpu_svm *svm) +{ + struct kvm_vcpu *vcpu = &svm->vcpu; + struct kvm *kvm = vcpu->kvm; + struct sev_apic_id_desc *desc; + unsigned int nr_vcpus, size; + unsigned int i; + gpa_t gpa, end_gpa; + u64 pages; + + nr_vcpus = atomic_read(&kvm->online_vcpus); + size = sizeof(*desc) + (nr_vcpus * sizeof(desc->apic_ids[0])); + + pages = vcpu->arch.regs[VCPU_REGS_RAX]; + if (pages < PFN_UP(size)) { + vcpu->arch.regs[VCPU_REGS_RAX] = PFN_UP(size); + return 1; + } + + gpa = svm->vmcb->control.exit_info_1; + if (!PAGE_ALIGNED(gpa) || + check_add_overflow(gpa, size - 1, &end_gpa) || + !page_address_valid(vcpu, gpa) || + !page_address_valid(vcpu, end_gpa & PAGE_MASK)) + goto invalid_buffer; + + desc = kvzalloc(size, GFP_KERNEL_ACCOUNT); + if (!desc) + return -ENOMEM; + + desc->num_entries = nr_vcpus; + for (i = 0; i < nr_vcpus; i++) { + struct kvm_vcpu *listed_vcpu = kvm_get_vcpu(kvm, i); + + if (WARN_ON_ONCE(!listed_vcpu)) + goto invalid_buffer_free; + desc->apic_ids[i] = listed_vcpu->vcpu_id; + } + + if (kvm_write_guest(kvm, gpa, desc, size)) + goto invalid_buffer_free; + + kvfree(desc); + return 1; + +invalid_buffer_free: + kvfree(desc); +invalid_buffer: + svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT); + return 1; +} + static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa) { struct sev_data_snp_guest_request data = {0}; @@ -4539,6 +4599,7 @@ static bool is_snp_only_vmgexit(u64 exit_code) { switch (exit_code) { case SVM_VMGEXIT_AP_CREATION: + case SVM_VMGEXIT_GET_APIC_IDS: case SVM_VMGEXIT_GUEST_REQUEST: case SVM_VMGEXIT_EXT_GUEST_REQUEST: case SVM_VMGEXIT_PSC: @@ -4710,6 +4771,8 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) if (sev_snp_ap_creation(svm)) svm_vmgexit_bad_input(svm, GHCB_ERR_INVALID_INPUT); return 1; + case SVM_VMGEXIT_GET_APIC_IDS: + return sev_snp_get_apic_ids(svm); case SVM_VMGEXIT_GUEST_REQUEST: case SVM_VMGEXIT_EXT_GUEST_REQUEST: if (!PAGE_ALIGNED(control->exit_info_1) || -- 2.53.0