[PATCH v2 10/13] x86/kvm/emulate: Remove fastops

Peter Zijlstra
2025-04-30T11:26:46Z

No more FASTOPs, remove the remains.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kvm/emulate.c | 172 -------------------------------------------------
1 file changed, 1 insertion(+), 171 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -167,7 +167,6 @@
#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) */
-#define Fastop ((u64)1 << 44) /* Use opcode::u.fastop */
#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 */
@@ -203,7 +202,6 @@ struct opcode {
const struct escape *esc;
const struct instr_dual *idual;
const struct mode_dual *mdual;
- void (*fastop)(struct fastop *fake);
} u;
int (*check_perm)(struct x86_emulate_ctxt *ctxt);
};
@@ -383,152 +381,6 @@ static int em_##op(struct x86_emulate_ct
ON64(case 8: COP_ASM3(op##q, rax, rdx, cl); break;) \
COP_END

-
-/*
- * fastop functions have a special calling convention:
- *
- * dst: rax (in/out)
- * src: rdx (in/out)
- * src2: rcx (in)
- * flags: rflags (in/out)
- * ex: rsi (in:fastop pointer, out:zero if exception)
- *
- * Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
- * different operand sizes can be reached by calculation, rather than a jump
- * table (which would be bigger than the code).
- *
- * The 16 byte alignment, considering 5 bytes for the RET thunk, 3 for ENDBR
- * and 1 for the straight line speculation INT3, leaves 7 bytes for the
- * body of the function. Currently none is larger than 4.
- */
-static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
-
-#define FASTOP_SIZE 16
-
-#define __FOP_FUNC(name) \
- ".align " __stringify(FASTOP_SIZE) " \n\t" \
- ".type " name ", @function \n\t" \
- name ":\n\t" \
- ASM_ENDBR \
- IBT_NOSEAL(name)
-
-#define FOP_FUNC(name) \
- __FOP_FUNC(#name)
-
-#define __FOP_RET(name) \
- "11: " ASM_RET \
- ".size " name ", .-" name "\n\t"
-
-#define FOP_RET(name) \
- __FOP_RET(#name)
-
-#define __FOP_START(op, align) \
- extern void em_##op(struct fastop *fake); \
- asm(".pushsection .text, \"ax\" \n\t" \
- ".global em_" #op " \n\t" \
- ".align " __stringify(align) " \n\t" \
- "em_" #op ":\n\t"
-
-#define FOP_START(op) __FOP_START(op, FASTOP_SIZE)
-
-#define FOP_END \
- ".popsection")
-
-#define __FOPNOP(name) \
- __FOP_FUNC(name) \
- __FOP_RET(name)
-
-#define FOPNOP() \
- __FOPNOP(__stringify(__UNIQUE_ID(nop)))
-
-#define FOP1E(op, dst) \
- __FOP_FUNC(#op "_" #dst) \
- "10: " #op " %" #dst " \n\t" \
- __FOP_RET(#op "_" #dst)
-
-#define FOP1EEX(op, dst) \
- FOP1E(op, dst) _ASM_EXTABLE_TYPE_REG(10b, 11b, EX_TYPE_ZERO_REG, %%esi)
-
-#define FASTOP1(op) \
- FOP_START(op) \
- FOP1E(op##b, al) \
- FOP1E(op##w, ax) \
- FOP1E(op##l, eax) \
- ON64(FOP1E(op##q, rax)) \
- FOP_END
-
-/* 1-operand, using src2 (for MUL/DIV r/m) */
-#define FASTOP1SRC2(op, name) \
- FOP_START(name) \
- FOP1E(op, cl) \
- FOP1E(op, cx) \
- FOP1E(op, ecx) \
- ON64(FOP1E(op, rcx)) \
- FOP_END
-
-/* 1-operand, using src2 (for MUL/DIV r/m), with exceptions */
-#define FASTOP1SRC2EX(op, name) \
- FOP_START(name) \
- FOP1EEX(op, cl) \
- FOP1EEX(op, cx) \
- FOP1EEX(op, ecx) \
- ON64(FOP1EEX(op, rcx)) \
- FOP_END
-
-#define FOP2E(op, dst, src) \
- __FOP_FUNC(#op "_" #dst "_" #src) \
- #op " %" #src ", %" #dst " \n\t" \
- __FOP_RET(#op "_" #dst "_" #src)
-
-#define FASTOP2(op) \
- FOP_START(op) \
- FOP2E(op##b, al, dl) \
- FOP2E(op##w, ax, dx) \
- FOP2E(op##l, eax, edx) \
- ON64(FOP2E(op##q, rax, rdx)) \
- FOP_END
-
-/* 2 operand, word only */
-#define FASTOP2W(op) \
- FOP_START(op) \
- FOPNOP() \
- FOP2E(op##w, ax, dx) \
- FOP2E(op##l, eax, edx) \
- ON64(FOP2E(op##q, rax, rdx)) \
- FOP_END
-
-/* 2 operand, src is CL */
-#define FASTOP2CL(op) \
- FOP_START(op) \
- FOP2E(op##b, al, cl) \
- FOP2E(op##w, ax, cl) \
- FOP2E(op##l, eax, cl) \
- ON64(FOP2E(op##q, rax, cl)) \
- FOP_END
-
-/* 2 operand, src and dest are reversed */
-#define FASTOP2R(op, name) \
- FOP_START(name) \
- FOP2E(op##b, dl, al) \
- FOP2E(op##w, dx, ax) \
- FOP2E(op##l, edx, eax) \
- ON64(FOP2E(op##q, rdx, rax)) \
- FOP_END
-
-#define FOP3E(op, dst, src, src2) \
- __FOP_FUNC(#op "_" #dst "_" #src "_" #src2) \
- #op " %" #src2 ", %" #src ", %" #dst " \n\t"\
- __FOP_RET(#op "_" #dst "_" #src "_" #src2)
-
-/* 3-operand, word-only, src2=cl */
-#define FASTOP3WCL(op) \
- FOP_START(op) \
- FOPNOP() \
- FOP3E(op##w, ax, dx, cl) \
- FOP3E(op##l, eax, edx, cl) \
- ON64(FOP3E(op##q, rax, rdx, cl)) \
- FOP_END
-
static int em_salc(struct x86_emulate_ctxt *ctxt)
{
/*
@@ -4052,7 +3904,6 @@ static int check_perm_out(struct x86_emu
#define MD(_f, _m) { .flags = ((_f) | ModeDual), .u.mdual = (_m) }
#define E(_f, _e) { .flags = ((_f) | Escape | ModRM), .u.esc = (_e) }
#define I(_f, _e) { .flags = (_f), .u.execute = (_e) }
-#define F(_f, _e) { .flags = (_f) | Fastop, .u.fastop = (_e) }
#define II(_f, _e, _i) \
{ .flags = (_f)|Intercept, .u.execute = (_e), .intercept = x86_intercept_##_i }
#define IIP(_f, _e, _i, _p) \
@@ -5158,24 +5009,6 @@ static void fetch_possible_mmx_operand(s
kvm_read_mmx_reg(op->addr.mm, &op->mm_val);
}

-static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop)
-{
- ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;
-
- if (!(ctxt->d & ByteOp))
- fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
-
- asm("push %[flags]; popf; " CALL_NOSPEC " ; pushf; pop %[flags]\n"
- : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
- [thunk_target]"+S"(fop), ASM_CALL_CONSTRAINT
- : "c"(ctxt->src2.val));
-
- ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);
- if (!fop) /* exception is returned in fop variable */
- return emulate_de(ctxt);
- return X86EMUL_CONTINUE;
-}
-
void init_decode_cache(struct x86_emulate_ctxt *ctxt)
{
/* Clear fields that are set conditionally but read without a guard. */
@@ -5340,10 +5173,7 @@ int x86_emulate_insn(struct x86_emulate_
ctxt->eflags &= ~X86_EFLAGS_RF;

if (ctxt->execute) {
- if (ctxt->d & Fastop)
- rc = fastop(ctxt, ctxt->fop);
- else
- rc = ctxt->execute(ctxt);
+ rc = ctxt->execute(ctxt);
if (rc != X86EMUL_CONTINUE)
goto done;
goto writeback;