[PATCH 03/10] KVM: emulate: improve formatting of flags table

Paolo Bonzini
2025-11-14T00:36:42Z

Align a little better the comments on the right side and list
explicitly the bits used by multi-bit fields.

No functional change intended.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/emulate.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 57799b5d9da2..28f81346878e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -81,9 +81,8 @@
*/

/* Operand sizes: 8-bit operands or specified/overridden size. */
-#define ByteOp (1<<0) /* 8-bit operands. */
-/* Destination operand type. */
-#define DstShift 1
+#define ByteOp (1<<0) /* 8-bit operands. */
+#define DstShift 1 /* Destination operand type at bits 1-5 */
#define ImplicitOps (OpImplicit << DstShift)
#define DstReg (OpReg << DstShift)
#define DstMem (OpMem << DstShift)
@@ -95,8 +94,7 @@
#define DstDX (OpDX << DstShift)
#define DstAccLo (OpAccLo << DstShift)
#define DstMask (OpMask << DstShift)
-/* Source operand type. */
-#define SrcShift 6
+#define SrcShift 6 /* Source operand type at bits 6-10 */
#define SrcNone (OpNone << SrcShift)
#define SrcReg (OpReg << SrcShift)
#define SrcMem (OpMem << SrcShift)
@@ -119,10 +117,10 @@
#define SrcAccHi (OpAccHi << SrcShift)
#define SrcMask (OpMask << SrcShift)
#define BitOp (1<<11)
-#define MemAbs (1<<12) /* Memory operand is absolute displacement */
+#define MemAbs (1<<12) /* Memory operand is absolute displacement */
#define String (1<<13) /* String instruction (rep capable) */
#define Stack (1<<14) /* Stack instruction (push/pop) */
-#define GroupMask (7<<15) /* Opcode uses one of the group mechanisms */
+#define GroupMask (7<<15) /* Group mechanisms, at bits 15-17 */
#define Group (1<<15) /* Bits 3:5 of modrm byte extend opcode */
#define GroupDual (2<<15) /* Alternate decoding of mod == 3 */
#define Prefix (3<<15) /* Instruction varies with 66/f2/f3 prefix */
@@ -131,11 +129,8 @@
#define InstrDual (6<<15) /* Alternate instruction decoding of mod == 3 */
#define ModeDual (7<<15) /* Different instruction for 32/64 bit */
#define Sse (1<<18) /* SSE Vector instruction */
-/* Generic ModRM decode. */
-#define ModRM (1<<19)
-/* Destination is only written; never read. */
-#define Mov (1<<20)
-/* Misc flags */
+#define ModRM (1<<19) /* Generic ModRM decode. */
+#define Mov (1<<20) /* Destination is only written; never read. */
#define Prot (1<<21) /* instruction generates #UD if not in prot-mode */
#define EmulateOnUD (1<<22) /* Emulate if unsupported by the host */
#define NoAccess (1<<23) /* Don't access memory (lea/invlpg/verr etc) */
@@ -143,11 +138,10 @@
#define Undefined (1<<25) /* No Such Instruction */
#define Lock (1<<26) /* lock prefix is allowed for the instruction */
#define Priv (1<<27) /* instruction generates #GP if current CPL != 0 */
-#define No64 (1<<28)
+#define No64 (1<<28) /* Instruction generates #UD in 64-bit mode */
#define PageTable (1 << 29) /* instruction used to write page table */
#define NotImpl (1 << 30) /* instruction is not implemented */
-/* Source 2 operand type */
-#define Src2Shift (32) /* bits 32-36 */
+#define Src2Shift (32) /* Source 2 operand type at bits 32-36 */
#define Src2None (OpNone << Src2Shift)
#define Src2Mem (OpMem << Src2Shift)
#define Src2CL (OpCL << Src2Shift)
@@ -163,11 +157,12 @@
#define Src2Mask (OpMask << Src2Shift)
/* free: 37-39 */
#define Mmx ((u64)1 << 40) /* MMX Vector instruction */
-#define AlignMask ((u64)7 << 41)
+#define AlignMask ((u64)7 << 41) /* Memory alignment requirement at bits 41-43 */
#define Aligned ((u64)1 << 41) /* Explicitly aligned (e.g. MOVDQA) */
#define Unaligned ((u64)2 << 41) /* Explicitly unaligned (e.g. MOVDQU) */
#define Avx ((u64)3 << 41) /* Advanced Vector Extensions */
#define Aligned16 ((u64)4 << 41) /* Aligned to 16 byte boundary (e.g. FXSAVE) */
+/* free: 44 */
#define NoWrite ((u64)1 << 45) /* No writeback */
#define SrcWrite ((u64)1 << 46) /* Write back src operand */
#define NoMod ((u64)1 << 47) /* Mod field is ignored */
--
2.43.5