Re: [PATCH 3/9] x86emul: drop regs field from emulator state structure

[Andrew Cooper]

On 04/04/2023 3:51 pm, Jan Beulich wrote:
> For an unclear reason 0552a8cfda43 ("x86emul: track only rIP in emulator
> state") converted the original struct cpu_user_regs instance to a
> pointer, rather than dropping the field altogether: The pointer merely
> aliases the one in the context structure.
>
> Signed-off-by: Jan Beulich 

Acked-by: Andrew Cooper 

[PATCH 3/9] x86emul: drop regs field from emulator state structure

[Jan Beulich]

For an unclear reason 0552a8cfda43 ("x86emul: track only rIP in emulator
state") converted the original struct cpu_user_regs instance to a
pointer, rather than dropping the field altogether: The pointer merely
aliases the one in the context structure.

Signed-off-by: Jan Beulich 

--- a/xen/arch/x86/x86_emulate/decode.c
+++ b/xen/arch/x86/x86_emulate/decode.c
@@ -1013,7 +1013,6 @@ int x86emul_decode(struct x86_emulate_st
 s->ea.type = OP_NONE;
 s->ea.mem.seg = x86_seg_ds;
 s->ea.reg = PTR_POISON;
-s->regs = ctxt->regs;
 s->ip = ctxt->regs->r(ip);
 
 s->op_bytes = def_op_bytes = ad_bytes = def_ad_bytes =
@@ -1129,7 +1128,7 @@ int x86emul_decode(struct x86_emulate_st
 default:
 BUG(); /* Shouldn't be possible. */
 case 2:
-if ( s->regs->eflags & X86_EFLAGS_VM )
+if ( ctxt->regs->eflags & X86_EFLAGS_VM )
 break;
 /* fall through */
 case 4:
@@ -1458,33 +1457,33 @@ int x86emul_decode(struct x86_emulate_st
 switch ( s->modrm_rm )
 {
 case 0:
-s->ea.mem.off = s->regs->bx + s->regs->si;
+s->ea.mem.off = ctxt->regs->bx + ctxt->regs->si;
 break;
 case 1:
-s->ea.mem.off = s->regs->bx + s->regs->di;
+s->ea.mem.off = ctxt->regs->bx + ctxt->regs->di;
 break;
 case 2:
 s->ea.mem.seg = x86_seg_ss;
-s->ea.mem.off = s->regs->bp + s->regs->si;
+s->ea.mem.off = ctxt->regs->bp + ctxt->regs->si;
 break;
 case 3:
 s->ea.mem.seg = x86_seg_ss;
-s->ea.mem.off = s->regs->bp + s->regs->di;
+s->ea.mem.off = ctxt->regs->bp + ctxt->regs->di;
 break;
 case 4:
-s->ea.mem.off = s->regs->si;
+s->ea.mem.off = ctxt->regs->si;
 break;
 case 5:
-s->ea.mem.off = s->regs->di;
+s->ea.mem.off = ctxt->regs->di;
 break;
 case 6:
 if ( s->modrm_mod == 0 )
 break;
 s->ea.mem.seg = x86_seg_ss;
-s->ea.mem.off = s->regs->bp;
+s->ea.mem.off = ctxt->regs->bp;
 break;
 case 7:
-s->ea.mem.off = s->regs->bx;
+s->ea.mem.off = ctxt->regs->bx;
 break;
 }
 switch ( s->modrm_mod )
@@ -1517,7 +1516,7 @@ int x86emul_decode(struct x86_emulate_st
  !s->evex.RX) << 4;
 else if ( s->sib_index != 4 )
 {
-s->ea.mem.off = *decode_gpr(s->regs, s->sib_index);
+s->ea.mem.off = *decode_gpr(ctxt->regs, s->sib_index);
 s->ea.mem.off <<= s->sib_scale;
 }
 if ( (s->modrm_mod == 0) && ((sib_base & 7) == 5) )
@@ -1525,7 +1524,7 @@ int x86emul_decode(struct x86_emulate_st
 else if ( sib_base == 4 )
 {
 s->ea.mem.seg  = x86_seg_ss;
-s->ea.mem.off += s->regs->r(sp);
+s->ea.mem.off += ctxt->regs->r(sp);
 if ( !s->ext && (b == 0x8f) )
 /* POP  computes its EA post increment. */
 s->ea.mem.off += ((mode_64bit() && (s->op_bytes == 4))
@@ -1534,16 +1533,16 @@ int x86emul_decode(struct x86_emulate_st
 else if ( sib_base == 5 )
 {
 s->ea.mem.seg  = x86_seg_ss;
-s->ea.mem.off += s->regs->r(bp);
+s->ea.mem.off += ctxt->regs->r(bp);
 }
 else
-s->ea.mem.off += *decode_gpr(s->regs, sib_base);
+s->ea.mem.off += *decode_gpr(ctxt->regs, sib_base);
 }
 else
 {
 generate_exception_if(d & vSIB, X86_EXC_UD);
 s->modrm_rm |= (s->rex_prefix & 1) << 3;
-s->ea.mem.off = *decode_gpr(s->regs, s->modrm_rm);
+s->ea.mem.off = *decode_gpr(ctxt->regs, s->modrm_rm);
 if ( (s->modrm_rm == 5) && (s->modrm_mod != 0) )
 s->ea.mem.seg = x86_seg_ss;
 }
--- a/xen/arch/x86/x86_emulate/private.h
+++ b/xen/arch/x86/x86_emulate/private.h
@@ -321,7 +321,6 @@ struct x86_emulate_state {
 #define imm2 ea.orig_val
 
 unsigned long ip;
-struct cpu_user_regs *regs;
 
 #ifndef NDEBUG
 /*