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Shutemov" X-Google-Original-From: "Kirill A. Shutemov" Received: by box.localdomain (Postfix, from userid 1000) id DF87210309C; Mon, 18 Oct 2021 19:56:20 +0300 (+03) To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Tom Lendacky , Joerg Roedel Cc: Kuppuswamy Sathyanarayanan , Andi Kleen , Dave Hansen , Sean Christopherson , Peter Zijlstra , x86@kernel.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Tony Luck Subject: [PATCHv2 2/3] x86/insn-eval: Introduce insn_decode_mmio() Date: Mon, 18 Oct 2021 19:56:13 +0300 Message-Id: <20211018165614.20153-3-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20211018165614.20153-1-kirill.shutemov@linux.intel.com> References: <20211018165614.20153-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In preparation for sharing MMIO instruction decode between SEV-ES and TDX, factor out the common decode into a new insn_decode_mmio() helper. For regular virtual machine, MMIO is handled by the VMM and KVM emulates instructions that caused MMIO. But, this model doesn't work for a secure VMs (like SEV or TDX) as VMM doesn't have access to the guest memory and register state. So, for TDX or SEV VMM needs assistance in handling MMIO. It induces exception in the guest. Guest has to decode the instruction and handle it on its own. The code is based on the current SEV MMIO implementation. Signed-off-by: Kirill A. Shutemov Reviewed-by: Andi Kleen Reviewed-by: Tony Luck --- arch/x86/include/asm/insn-eval.h | 12 +++++ arch/x86/lib/insn-eval.c | 84 ++++++++++++++++++++++++++++++++ 2 files changed, 96 insertions(+) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 5c6869565fb3..010d31726d06 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -29,4 +29,16 @@ int insn_fetch_from_user_inatomic(struct pt_regs *regs, bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE], int buf_size); +enum mmio_type { + MMIO_DECODE_FAILED, + MMIO_WRITE, + MMIO_WRITE_IMM, + MMIO_READ, + MMIO_READ_ZERO_EXTEND, + MMIO_READ_SIGN_EXTEND, + MMIO_MOVS, +}; + +enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes); + #endif /* _ASM_X86_INSN_EVAL_H */ diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 64fbab09b966..1714359f48bd 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -1559,3 +1559,87 @@ bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, return true; } + +/** + * insn_decode_mmio() - Decode a MMIO instruction + * @insn: Structure to store decoded instruction + * @bytes: Returns size of memory operand + * + * Decodes instruction that used for Memory-mapped I/O. + * + * Returns: + * + * Type of the instruction. Size of the memory operand is stored in + * @bytes. If decode failed, MMIO_DECODE_FAILED returned. + */ +enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes) +{ + int type = MMIO_DECODE_FAILED; + + *bytes = 0; + + if (!insn_get_opcode(insn)) + return MMIO_DECODE_FAILED; + + switch (insn->opcode.bytes[0]) { + case 0x88: /* MOV m8,r8 */ + *bytes = 1; + fallthrough; + case 0x89: /* MOV m16/m32/m64, r16/m32/m64 */ + if (!*bytes) + *bytes = insn->opnd_bytes; + type = MMIO_WRITE; + break; + + case 0xc6: /* MOV m8, imm8 */ + *bytes = 1; + fallthrough; + case 0xc7: /* MOV m16/m32/m64, imm16/imm32/imm64 */ + if (!*bytes) + *bytes = insn->opnd_bytes; + type = MMIO_WRITE_IMM; + break; + + case 0x8a: /* MOV r8, m8 */ + *bytes = 1; + fallthrough; + case 0x8b: /* MOV r16/r32/r64, m16/m32/m64 */ + if (!*bytes) + *bytes = insn->opnd_bytes; + type = MMIO_READ; + break; + + case 0xa4: /* MOVS m8, m8 */ + *bytes = 1; + fallthrough; + case 0xa5: /* MOVS m16/m32/m64, m16/m32/m64 */ + if (!*bytes) + *bytes = insn->opnd_bytes; + type = MMIO_MOVS; + break; + + case 0x0f: /* Two-byte instruction */ + switch (insn->opcode.bytes[1]) { + case 0xb6: /* MOVZX r16/r32/r64, m8 */ + *bytes = 1; + fallthrough; + case 0xb7: /* MOVZX r32/r64, m16 */ + if (!*bytes) + *bytes = 2; + type = MMIO_READ_ZERO_EXTEND; + break; + + case 0xbe: /* MOVSX r16/r32/r64, m8 */ + *bytes = 1; + fallthrough; + case 0xbf: /* MOVSX r32/r64, m16 */ + if (!*bytes) + *bytes = 2; + type = MMIO_READ_SIGN_EXTEND; + break; + } + break; + } + + return type; +} -- 2.32.0