From patchwork Wed Aug 2 15:48:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 711055 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2A82C04A6A for ; Wed, 2 Aug 2023 15:51:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235446AbjHBPvt (ORCPT ); Wed, 2 Aug 2023 11:51:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235401AbjHBPvT (ORCPT ); Wed, 2 Aug 2023 11:51:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1263421A; Wed, 2 Aug 2023 08:50:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7B4D3619CB; Wed, 2 Aug 2023 15:50:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02953C433C8; Wed, 2 Aug 2023 15:50:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690991427; bh=Yft7wHndNsfc52pD9ceXPfBqRxkOxgMgHrWle8cF1T8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cp5KO99MUtPVMrkVdsw/gRBhXEFQIqQzEzk2xbZi8p1MS6flaVrcRPu3uWP8J5k9d LWdmbsYxzPOg086SIZvJGxqMeEX76VwJkAYz4OtmJmhL1gChLg+4qleeo0JKnlJXeh qll3eF541P4GexA5yl0AF/CRW3VaUr5KVysbW4meXi0DXPWDWsqMwYKae5mw99rm4u q2weMvyxMhfn7NkY69K2cajj7ObEkDqH5idXgRE7HWxb418OQDbwepn8MMUkK5jock OdH7yRLM10GD2/cuEXswyOowCW/h+Xp9qpr01cBVw2xH9SsqTQRxuMZA0k/Dxblrf8 XkboC0J1Trpkw== From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel , Evgeniy Baskov , Borislav Petkov , Andy Lutomirski , Dave Hansen , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Alexey Khoroshilov , Peter Jones , Gerd Hoffmann , Dave Young , Mario Limonciello , Kees Cook , Tom Lendacky , "Kirill A . Shutemov" , Linus Torvalds , Joerg Roedel Subject: [PATCH v8 22/23] x86/efistub: Perform SNP feature test while running in the firmware Date: Wed, 2 Aug 2023 17:48:30 +0200 Message-Id: <20230802154831.2147855-23-ardb@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230802154831.2147855-1-ardb@kernel.org> References: <20230802154831.2147855-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=7725; i=ardb@kernel.org; h=from:subject; bh=Yft7wHndNsfc52pD9ceXPfBqRxkOxgMgHrWle8cF1T8=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIeVU1dnHC+Lu/zZVm3SdbcLPO88PrdRg4uHkkp3rbpRXy +I7vfdhRykLgxgHg6yYIovA7L/vdp6eKFXrPEsWZg4rE8gQBi5OAZjI9XuMDL17J0Vsk+tcIcN9 9esObUVFhTdcM5m5Zqmd+M0ju3OLgCPDP535uuc/7T/q9PbRvG8ebLOUmJccF968Ovqupkyzmtw 3Qx4A X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org Before refactoring the EFI stub boot flow to avoid the legacy bare metal decompressor, duplicate the SNP feature check in the EFI stub before handing over to the kernel proper. The SNP feature check can be performed while running under the EFI boot services, which means it can force the boot to fail gracefully and return an error to the bootloader if the loaded kernel does not implement support for all the features that the hypervisor enabled. Signed-off-by: Ard Biesheuvel --- arch/x86/boot/compressed/sev.c | 112 ++++++++++++-------- arch/x86/include/asm/sev.h | 4 + drivers/firmware/efi/libstub/x86-stub.c | 17 +++ 3 files changed, 87 insertions(+), 46 deletions(-) diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index c3e343bd4760e0ab..199155b8af3bc535 100644 --- a/arch/x86/boot/compressed/sev.c +++ b/arch/x86/boot/compressed/sev.c @@ -367,20 +367,25 @@ static void enforce_vmpl0(void) */ #define SNP_FEATURES_PRESENT (0) +u64 snp_get_unsupported_features(u64 status) +{ + if (!(status & MSR_AMD64_SEV_SNP_ENABLED)) + return 0; + + return status & SNP_FEATURES_IMPL_REQ & ~SNP_FEATURES_PRESENT; +} + void snp_check_features(void) { u64 unsupported; - if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) - return; - /* * Terminate the boot if hypervisor has enabled any feature lacking * guest side implementation. Pass on the unsupported features mask through * EXIT_INFO_2 of the GHCB protocol so that those features can be reported * as part of the guest boot failure. */ - unsupported = sev_status & SNP_FEATURES_IMPL_REQ & ~SNP_FEATURES_PRESENT; + unsupported = snp_get_unsupported_features(sev_status); if (unsupported) { if (ghcb_version < 2 || (!boot_ghcb && !early_setup_ghcb())) sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED); @@ -390,10 +395,45 @@ void snp_check_features(void) } } -void sev_enable(struct boot_params *bp) +/* + * sev_check_cpu_support - Check for SEV support in the CPU capabilities + * + * Returns < 0 if SEV is not supported, otherwise the position of the + * encryption bit in the page table descriptors. + */ +static int sev_check_cpu_support(void) { unsigned int eax, ebx, ecx, edx; + + /* Check for the SME/SEV support leaf */ + eax = 0x80000000; + ecx = 0; + native_cpuid(&eax, &ebx, &ecx, &edx); + if (eax < 0x8000001f) + return -ENODEV; + + /* + * Check for the SME/SEV feature: + * CPUID Fn8000_001F[EAX] + * - Bit 0 - Secure Memory Encryption support + * - Bit 1 - Secure Encrypted Virtualization support + * CPUID Fn8000_001F[EBX] + * - Bits 5:0 - Pagetable bit position used to indicate encryption + */ + eax = 0x8000001f; + ecx = 0; + native_cpuid(&eax, &ebx, &ecx, &edx); + /* Check whether SEV is supported */ + if (!(eax & BIT(1))) + return -ENODEV; + + return ebx & 0x3f; +} + +void sev_enable(struct boot_params *bp) +{ struct msr m; + int bitpos; bool snp; /* @@ -413,26 +453,7 @@ void sev_enable(struct boot_params *bp) * which is good enough. */ - /* Check for the SME/SEV support leaf */ - eax = 0x80000000; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - if (eax < 0x8000001f) - return; - - /* - * Check for the SME/SEV feature: - * CPUID Fn8000_001F[EAX] - * - Bit 0 - Secure Memory Encryption support - * - Bit 1 - Secure Encrypted Virtualization support - * CPUID Fn8000_001F[EBX] - * - Bits 5:0 - Pagetable bit position used to indicate encryption - */ - eax = 0x8000001f; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - /* Check whether SEV is supported */ - if (!(eax & BIT(1))) + if (sev_check_cpu_support() < 0) return; /* @@ -443,26 +464,8 @@ void sev_enable(struct boot_params *bp) /* Now repeat the checks with the SNP CPUID table. */ - /* Recheck the SME/SEV support leaf */ - eax = 0x80000000; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - if (eax < 0x8000001f) - return; - - /* - * Recheck for the SME/SEV feature: - * CPUID Fn8000_001F[EAX] - * - Bit 0 - Secure Memory Encryption support - * - Bit 1 - Secure Encrypted Virtualization support - * CPUID Fn8000_001F[EBX] - * - Bits 5:0 - Pagetable bit position used to indicate encryption - */ - eax = 0x8000001f; - ecx = 0; - native_cpuid(&eax, &ebx, &ecx, &edx); - /* Check whether SEV is supported */ - if (!(eax & BIT(1))) { + bitpos = sev_check_cpu_support(); + if (bitpos < 0) { if (snp) error("SEV-SNP support indicated by CC blob, but not CPUID."); return; @@ -494,7 +497,24 @@ void sev_enable(struct boot_params *bp) if (snp && !(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) error("SEV-SNP supported indicated by CC blob, but not SEV status MSR."); - sme_me_mask = BIT_ULL(ebx & 0x3f); + sme_me_mask = BIT_ULL(bitpos); +} + +/* + * sev_get_status - Retrieve the SEV status mask + * + * Returns 0 if the CPU is not SEV capable, otherwise the value of the + * AMD64_SEV MSR. + */ +u64 sev_get_status(void) +{ + struct msr m; + + if (sev_check_cpu_support() < 0) + return 0; + + boot_rdmsr(MSR_AMD64_SEV, &m); + return m.q; } /* Search for Confidential Computing blob in the EFI config table. */ diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 66c806784c5256bd..b97d239e18ea25fc 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -210,6 +210,8 @@ bool snp_init(struct boot_params *bp); void __init __noreturn snp_abort(void); int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio); void snp_accept_memory(phys_addr_t start, phys_addr_t end); +u64 snp_get_unsupported_features(u64 status); +u64 sev_get_status(void); #else static inline void sev_es_ist_enter(struct pt_regs *regs) { } static inline void sev_es_ist_exit(void) { } @@ -235,6 +237,8 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in } static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { } +static inline u64 snp_get_unsupported_features(u64 status) { return 0; } +static inline u64 sev_get_status(void) { return 0; } #endif #endif diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index acb1c65bf8ac6fb3..b4685da2b8d5c243 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -15,6 +15,7 @@ #include #include #include +#include #include "efistub.h" #include "x86-stub.h" @@ -790,6 +791,19 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle) return EFI_SUCCESS; } +static bool have_unsupported_snp_features(void) +{ + u64 unsupported; + + unsupported = snp_get_unsupported_features(sev_get_status()); + if (unsupported) { + efi_err("Unsupported SEV-SNP features detected: 0x%llx\n", + unsupported); + return true; + } + return false; +} + static void __noreturn enter_kernel(unsigned long kernel_addr, struct boot_params *boot_params) { @@ -820,6 +834,9 @@ void __noreturn efi_stub_entry(efi_handle_t handle, if (efi_system_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE) efi_exit(handle, EFI_INVALID_PARAMETER); + if (have_unsupported_snp_features()) + efi_exit(handle, EFI_UNSUPPORTED); + if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) { efi_dxe_table = get_efi_config_table(EFI_DXE_SERVICES_TABLE_GUID); if (efi_dxe_table &&