[kvm-unit-tests,RFC,02/17] x86 TDX: Add #VE handler

Commit Message

Duan, Zhenzhong March 3, 2022, 7:18 a.m. UTC

Some instructions execution trigger #VE and are simulated in #VE
handler.

Add such a handler, currently support simulation of IO and MSR
read/write, cpuid and hlt instructions.

Signed-off-by: Zhenzhong Duan <[e-mail]>
Reviewed-by: Yu Zhang <[e-mail]>
---
 lib/x86/desc.c      |  3 ++
 lib/x86/processor.h |  1 +
 lib/x86/tdx.c       | 87 +++++++++++++++++++++++++++++++++++++++++++++
 lib/x86/tdx.h       | 17 +++++++++
 4 files changed, 108 insertions(+)

Patch

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index c2eb16e91fa1..b35274e44a8d 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -112,6 +112,7 @@  const char* exception_mnemonic(int vector)
 	case 17: return "#AC";
 	case 18: return "#MC";
 	case 19: return "#XM";
+	case 20: return "#VE";
 	default: return "#??";
 	}
 }
@@ -227,6 +228,7 @@  EX(mf, 16);
 EX_E(ac, 17);
 EX(mc, 18);
 EX(xm, 19);
+EX(ve, 20);
 EX_E(cp, 21);
 
 asm (".pushsection .text \n\t"
@@ -273,6 +275,7 @@  static void *idt_handlers[32] = {
 	[17] = &ac_fault,
 	[18] = &mc_fault,
 	[19] = &xm_fault,
+	[20] = &ve_fault,
 	[21] = &cp_fault,
 };
 
diff --git a/lib/x86/processor.h b/lib/x86/processor.h
index 117032a4895c..865269fd3857 100644
--- a/lib/x86/processor.h
+++ b/lib/x86/processor.h
@@ -28,6 +28,7 @@ 
 #define GP_VECTOR 13
 #define PF_VECTOR 14
 #define AC_VECTOR 17
+#define VE_VECTOR 20
 #define CP_VECTOR 21
 
 #define X86_CR0_PE	0x00000001
diff --git a/lib/x86/tdx.c b/lib/x86/tdx.c
index 8308480105d6..42ab25f47e57 100644
--- a/lib/x86/tdx.c
+++ b/lib/x86/tdx.c
@@ -267,10 +267,97 @@  static bool tdx_handle_io(struct ex_regs *regs, u32 exit_qual)
 	return ret ? false : true;
 }
 
+static bool tdx_get_ve_info(struct ve_info *ve)
+{
+	struct tdx_module_output out;
+	u64 ret;
+
+	if (!ve)
+		return false;
+
+	/*
+	 * NMIs and machine checks are suppressed. Before this point any
+	 * #VE is fatal. After this point (TDGETVEINFO call), NMIs and
+	 * additional #VEs are permitted (but it is expected not to
+	 * happen unless kernel panics).
+	 */
+	ret = __tdx_module_call(TDX_GET_VEINFO, 0, 0, 0, 0, &out);
+	if (ret)
+		return false;
+
+	ve->exit_reason = out.rcx;
+	ve->exit_qual	= out.rdx;
+	ve->gla		= out.r8;
+	ve->gpa		= out.r9;
+	ve->instr_len	= out.r10 & UINT_MAX;
+	ve->instr_info	= out.r10 >> 32;
+
+	return true;
+}
+
+static bool tdx_handle_virtualization_exception(struct ex_regs *regs,
+		struct ve_info *ve)
+{
+	bool ret = true;
+	u64 val = ~0ULL;
+	bool do_sti;
+
+	switch (ve->exit_reason) {
+	case EXIT_REASON_HLT:
+		do_sti = !!(regs->rflags & X86_EFLAGS_IF);
+		/* Bypass failed hlt is better than hang */
+		if (!_tdx_halt(!do_sti, do_sti))
+			tdx_printf("HLT instruction emulation failed\n");
+		break;
+	case EXIT_REASON_MSR_READ:
+		ret = tdx_read_msr(regs->rcx, &val);
+		if (ret) {
+			regs->rax = (u32)val;
+			regs->rdx = val >> 32;
+		}
+		break;
+	case EXIT_REASON_MSR_WRITE:
+		ret = tdx_write_msr(regs->rcx, regs->rax, regs->rdx);
+		break;
+	case EXIT_REASON_CPUID:
+		ret = tdx_handle_cpuid(regs);
+		break;
+	case EXIT_REASON_IO_INSTRUCTION:
+		ret = tdx_handle_io(regs, ve->exit_qual);
+		break;
+	default:
+		tdx_printf("Unexpected #VE: %ld\n", ve->exit_reason);
+		return false;
+	}
+
+	/* After successful #VE handling, move the IP */
+	if (ret)
+		regs->rip += ve->instr_len;
+
+	return ret;
+}
+
+/* #VE exception handler. */
+static void tdx_handle_ve(struct ex_regs *regs)
+{
+	struct ve_info ve;
+
+	if (!tdx_get_ve_info(&ve)) {
+		tdx_printf("tdx_get_ve_info failed\n");
+		return;
+	}
+
+	tdx_handle_virtualization_exception(regs, &ve);
+}
+
 efi_status_t setup_tdx(void)
 {
 	if (!is_tdx_guest())
 		return EFI_UNSUPPORTED;
 
+	handle_exception(20, tdx_handle_ve);
+
+	printf("Initialized TDX.\n");
+
 	return EFI_SUCCESS;
 }
diff --git a/lib/x86/tdx.h b/lib/x86/tdx.h
index 92ae5277b04d..68ddc136d1d9 100644
--- a/lib/x86/tdx.h
+++ b/lib/x86/tdx.h
@@ -29,6 +29,9 @@ 
 #define EXIT_REASON_MSR_READ            31
 #define EXIT_REASON_MSR_WRITE           32
 
+/* TDX Module call Leaf IDs */
+#define TDX_GET_VEINFO			3
+
 /*
  * Used in __tdx_module_call() helper function to gather the
  * output registers' values of TDCALL instruction when requesting
@@ -59,6 +62,20 @@  struct tdx_hypercall_output {
 	u64 r15;
 };
 
+/*
+ * Used by #VE exception handler to gather the #VE exception
+ * info from the TDX module. This is software only structure
+ * and not related to TDX module/VMM.
+ */
+struct ve_info {
+	u64 exit_reason;
+	u64 exit_qual;
+	u64 gla;	/* Guest Linear (virtual) Address */
+	u64 gpa;	/* Guest Physical (virtual) Address */
+	u32 instr_len;
+	u32 instr_info;
+};
+
 bool is_tdx_guest(void);
 efi_status_t setup_tdx(void);