From mboxrd@z Thu Jan 1 00:00:00 1970 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 210BAC433F5 for ; Sat, 9 Apr 2022 01:29:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240490AbiDIBb3 (ORCPT ); Fri, 8 Apr 2022 21:31:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240405AbiDIBa0 (ORCPT ); Fri, 8 Apr 2022 21:30:26 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 585F5119253; Fri, 8 Apr 2022 18:27:44 -0700 (PDT) Date: Sat, 09 Apr 2022 01:27:41 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1649467663; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=34MR+1FTRQCYUVSLmQIaHUzNox5VfuiuN6xRhP+kKhA=; b=CzYv3JQyjqK4mFnzPtK1wPZttrNGBLqCN5pa+y/jwDxv3KYRAer9XDTSUZs2cXVSop7EH3 RkdG7QkniRjuZQQwYPRKd9aiv7U++PO8JEXcpheGMQCzTTIPreEjJ53+BUTBzZbXv/1fHp /li4DMXP/W16nVNeHxPQpwm/yo7kht3tdtXxv88NpzpiKaPYOiUr6/6awYW2sFtCtGmJzT rNlF78IIQD8RlBcLBS0VA18PjDidvoc7spWt+4SDba0GgUEV6N3bw3pYmABVSBmeL1jDa9 CqgODGo5YruFxFTHz7v1CtJxdGeQtHS2lBgIlX67IBir5IWTnBuhkXLlxyxwRw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1649467663; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=34MR+1FTRQCYUVSLmQIaHUzNox5VfuiuN6xRhP+kKhA=; b=PTGOyzb9OXGRWgBQaENf+Ey8eA4tiDF6DIjSSZNvgjSf/bZyFtyOndquaRm4GSFwbmPtpn Dv8Zc2EiUA8MMTDg== From: "tip-bot2 for Kuppuswamy Sathyanarayanan" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/tdx] x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Cc: Kuppuswamy Sathyanarayanan , "Kirill A. Shutemov" , Dave Hansen , Tony Luck , Thomas Gleixner , Borislav Petkov , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220405232939.73860-4-kirill.shutemov@linux.intel.com> References: <20220405232939.73860-4-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Message-ID: <164946766187.4207.15170758896351389068.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/tdx branch of tip: Commit-ID: eb94f1b6a70a683040d60d21bbb6ad65f082600a Gitweb: https://git.kernel.org/tip/eb94f1b6a70a683040d60d21bbb6ad65f082600a Author: Kuppuswamy Sathyanarayanan AuthorDate: Wed, 06 Apr 2022 02:29:12 +03:00 Committer: Dave Hansen CommitterDate: Thu, 07 Apr 2022 08:27:50 -07:00 x86/tdx: Add __tdx_module_call() and __tdx_hypercall() helper functions Guests communicate with VMMs with hypercalls. Historically, these are implemented using instructions that are known to cause VMEXITs like VMCALL, VMLAUNCH, etc. However, with TDX, VMEXITs no longer expose the guest state to the host. This prevents the old hypercall mechanisms from working. So, to communicate with VMM, TDX specification defines a new instruction called TDCALL. In a TDX based VM, since the VMM is an untrusted entity, an intermediary layer -- TDX module -- facilitates secure communication between the host and the guest. TDX module is loaded like a firmware into a special CPU mode called SEAM. TDX guests communicate with the TDX module using the TDCALL instruction. A guest uses TDCALL to communicate with both the TDX module and VMM. The value of the RAX register when executing the TDCALL instruction is used to determine the TDCALL type. A leaf of TDCALL used to communicate with the VMM is called TDVMCALL. Add generic interfaces to communicate with the TDX module and VMM (using the TDCALL instruction). __tdx_module_call() - Used to communicate with the TDX module (via TDCALL instruction). __tdx_hypercall() - Used by the guest to request services from the VMM (via TDVMCALL leaf of TDCALL). Also define an additional wrapper _tdx_hypercall(), which adds error handling support for the TDCALL failure. The __tdx_module_call() and __tdx_hypercall() helper functions are implemented in assembly in a .S file. The TDCALL ABI requires shuffling arguments in and out of registers, which proved to be awkward with inline assembly. Just like syscalls, not all TDVMCALL use cases need to use the same number of argument registers. The implementation here picks the current worst-case scenario for TDCALL (4 registers). For TDCALLs with fewer than 4 arguments, there will end up being a few superfluous (cheap) instructions. But, this approach maximizes code reuse. For registers used by the TDCALL instruction, please check TDX GHCI specification, the section titled "TDCALL instruction" and "TDG.VP.VMCALL Interface". Based on previous patch by Sean Christopherson. Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Tony Luck Reviewed-by: Dave Hansen Reviewed-by: Thomas Gleixner Reviewed-by: Borislav Petkov Link: https://lkml.kernel.org/r/20220405232939.73860-4-kirill.shutemov@linux.intel.com --- arch/x86/coco/tdx/Makefile | 2 +- arch/x86/coco/tdx/tdcall.S | 191 +++++++++++++++++++++++++++++++++- arch/x86/coco/tdx/tdx.c | 24 ++++- arch/x86/include/asm/tdx.h | 30 +++++- arch/x86/kernel/asm-offsets.c | 8 +- 5 files changed, 254 insertions(+), 1 deletion(-) create mode 100644 arch/x86/coco/tdx/tdcall.S diff --git a/arch/x86/coco/tdx/Makefile b/arch/x86/coco/tdx/Makefile index c929d53..46c5599 100644 --- a/arch/x86/coco/tdx/Makefile +++ b/arch/x86/coco/tdx/Makefile @@ -1,3 +1,3 @@ # SPDX-License-Identifier: GPL-2.0 -obj-y += tdx.o +obj-y += tdx.o tdcall.o diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S new file mode 100644 index 0000000..662479c --- /dev/null +++ b/arch/x86/coco/tdx/tdcall.S @@ -0,0 +1,191 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include +#include +#include +#include + +#include +#include +#include + +#include "../../virt/vmx/tdx/tdxcall.S" + +/* + * Bitmasks of exposed registers (with VMM). + */ +#define TDX_R10 BIT(10) +#define TDX_R11 BIT(11) +#define TDX_R12 BIT(12) +#define TDX_R13 BIT(13) +#define TDX_R14 BIT(14) +#define TDX_R15 BIT(15) + +/* + * These registers are clobbered to hold arguments for each + * TDVMCALL. They are safe to expose to the VMM. + * Each bit in this mask represents a register ID. Bit field + * details can be found in TDX GHCI specification, section + * titled "TDCALL [TDG.VP.VMCALL] leaf". + */ +#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \ + TDX_R12 | TDX_R13 | \ + TDX_R14 | TDX_R15 ) + +/* + * __tdx_module_call() - Used by TDX guests to request services from + * the TDX module (does not include VMM services) using TDCALL instruction. + * + * Transforms function call register arguments into the TDCALL register ABI. + * After TDCALL operation, TDX module output is saved in @out (if it is + * provided by the user). + * + *------------------------------------------------------------------------- + * TDCALL ABI: + *------------------------------------------------------------------------- + * Input Registers: + * + * RAX - TDCALL Leaf number. + * RCX,RDX,R8-R9 - TDCALL Leaf specific input registers. + * + * Output Registers: + * + * RAX - TDCALL instruction error code. + * RCX,RDX,R8-R11 - TDCALL Leaf specific output registers. + * + *------------------------------------------------------------------------- + * + * __tdx_module_call() function ABI: + * + * @fn (RDI) - TDCALL Leaf ID, moved to RAX + * @rcx (RSI) - Input parameter 1, moved to RCX + * @rdx (RDX) - Input parameter 2, moved to RDX + * @r8 (RCX) - Input parameter 3, moved to R8 + * @r9 (R8) - Input parameter 4, moved to R9 + * + * @out (R9) - struct tdx_module_output pointer + * stored temporarily in R12 (not + * shared with the TDX module). It + * can be NULL. + * + * Return status of TDCALL via RAX. + */ +SYM_FUNC_START(__tdx_module_call) + FRAME_BEGIN + TDX_MODULE_CALL host=0 + FRAME_END + ret +SYM_FUNC_END(__tdx_module_call) + +/* + * __tdx_hypercall() - Make hypercalls to a TDX VMM using TDVMCALL leaf + * of TDCALL instruction + * + * Transforms values in function call argument struct tdx_hypercall_args @args + * into the TDCALL register ABI. After TDCALL operation, VMM output is saved + * back in @args. + * + *------------------------------------------------------------------------- + * TD VMCALL ABI: + *------------------------------------------------------------------------- + * + * Input Registers: + * + * RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL) + * RCX - BITMAP which controls which part of TD Guest GPR + * is passed as-is to the VMM and back. + * R10 - Set 0 to indicate TDCALL follows standard TDX ABI + * specification. Non zero value indicates vendor + * specific ABI. + * R11 - VMCALL sub function number + * RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments. + * R8-R9, R12-R15 - Same as above. + * + * Output Registers: + * + * RAX - TDCALL instruction status (Not related to hypercall + * output). + * R10 - Hypercall output error code. + * R11-R15 - Hypercall sub function specific output values. + * + *------------------------------------------------------------------------- + * + * __tdx_hypercall() function ABI: + * + * @args (RDI) - struct tdx_hypercall_args for input and output + * @flags (RSI) - TDX_HCALL_* flags + * + * On successful completion, return the hypercall error code. + */ +SYM_FUNC_START(__tdx_hypercall) + FRAME_BEGIN + + /* Save callee-saved GPRs as mandated by the x86_64 ABI */ + push %r15 + push %r14 + push %r13 + push %r12 + + /* Mangle function call ABI into TDCALL ABI: */ + /* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */ + xor %eax, %eax + + /* Copy hypercall registers from arg struct: */ + movq TDX_HYPERCALL_r10(%rdi), %r10 + movq TDX_HYPERCALL_r11(%rdi), %r11 + movq TDX_HYPERCALL_r12(%rdi), %r12 + movq TDX_HYPERCALL_r13(%rdi), %r13 + movq TDX_HYPERCALL_r14(%rdi), %r14 + movq TDX_HYPERCALL_r15(%rdi), %r15 + + movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx + + tdcall + + /* + * RAX==0 indicates a failure of the TDVMCALL mechanism itself and that + * something has gone horribly wrong with the TDX module. + * + * The return status of the hypercall operation is in a separate + * register (in R10). Hypercall errors are a part of normal operation + * and are handled by callers. + */ + testq %rax, %rax + jne .Lpanic + + /* TDVMCALL leaf return code is in R10 */ + movq %r10, %rax + + /* Copy hypercall result registers to arg struct if needed */ + testq $TDX_HCALL_HAS_OUTPUT, %rsi + jz .Lout + + movq %r10, TDX_HYPERCALL_r10(%rdi) + movq %r11, TDX_HYPERCALL_r11(%rdi) + movq %r12, TDX_HYPERCALL_r12(%rdi) + movq %r13, TDX_HYPERCALL_r13(%rdi) + movq %r14, TDX_HYPERCALL_r14(%rdi) + movq %r15, TDX_HYPERCALL_r15(%rdi) +.Lout: + /* + * Zero out registers exposed to the VMM to avoid speculative execution + * with VMM-controlled values. This needs to include all registers + * present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15 + * context will be restored. + */ + xor %r10d, %r10d + xor %r11d, %r11d + + /* Restore callee-saved GPRs as mandated by the x86_64 ABI */ + pop %r12 + pop %r13 + pop %r14 + pop %r15 + + FRAME_END + + retq +.Lpanic: + call __tdx_hypercall_failed + /* __tdx_hypercall_failed never returns */ + jmp .Lpanic +SYM_FUNC_END(__tdx_hypercall) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 9767447..4b57880 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -7,6 +7,30 @@ #include #include +/* + * Wrapper for standard use of __tdx_hypercall with no output aside from + * return code. + */ +static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15) +{ + struct tdx_hypercall_args args = { + .r10 = TDX_HYPERCALL_STANDARD, + .r11 = fn, + .r12 = r12, + .r13 = r13, + .r14 = r14, + .r15 = r15, + }; + + return __tdx_hypercall(&args, 0); +} + +/* Called from __tdx_hypercall() for unrecoverable failure */ +void __tdx_hypercall_failed(void) +{ + panic("TDVMCALL failed. TDX module bug?"); +} + void __init tdx_early_init(void) { u32 eax, sig[3]; diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index cb4c4e6..a33d47a 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -3,12 +3,17 @@ #ifndef _ASM_X86_TDX_H #define _ASM_X86_TDX_H +#include #include #include #define TDX_CPUID_LEAF_ID 0x21 #define TDX_IDENT "IntelTDX " +#define TDX_HYPERCALL_STANDARD 0 + +#define TDX_HCALL_HAS_OUTPUT BIT(0) + /* * SW-defined error codes. * @@ -36,10 +41,35 @@ struct tdx_module_output { u64 r11; }; +/* + * Used in __tdx_hypercall() to pass down and get back registers' values of + * the TDCALL instruction when requesting services from the VMM. + * + * This is a software only structure and not part of the TDX module/VMM ABI. + */ +struct tdx_hypercall_args { + u64 r10; + u64 r11; + u64 r12; + u64 r13; + u64 r14; + u64 r15; +}; + #ifdef CONFIG_INTEL_TDX_GUEST void __init tdx_early_init(void); +/* Used to communicate with the TDX module */ +u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, + struct tdx_module_output *out); + +/* Used to request services from the VMM */ +u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags); + +/* Called from __tdx_hypercall() for unrecoverable failure */ +void __tdx_hypercall_failed(void); + #else static inline void tdx_early_init(void) { }; diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c index 7dca52f..4373080 100644 --- a/arch/x86/kernel/asm-offsets.c +++ b/arch/x86/kernel/asm-offsets.c @@ -75,6 +75,14 @@ static void __used common(void) OFFSET(TDX_MODULE_r11, tdx_module_output, r11); BLANK(); + OFFSET(TDX_HYPERCALL_r10, tdx_hypercall_args, r10); + OFFSET(TDX_HYPERCALL_r11, tdx_hypercall_args, r11); + OFFSET(TDX_HYPERCALL_r12, tdx_hypercall_args, r12); + OFFSET(TDX_HYPERCALL_r13, tdx_hypercall_args, r13); + OFFSET(TDX_HYPERCALL_r14, tdx_hypercall_args, r14); + OFFSET(TDX_HYPERCALL_r15, tdx_hypercall_args, r15); + + BLANK(); OFFSET(BP_scratch, boot_params, scratch); OFFSET(BP_secure_boot, boot_params, secure_boot); OFFSET(BP_loadflags, boot_params, hdr.loadflags);