MFamd64: Add support for extended FPU states on i386. This includes

support for AVX on i386.
- Similar to amd64, move the FPU save area out of the PCB and instead
  store saved FPU state in a variable-sized buffer after the PCB on the
  stack.
- To support the variable PCB location, alter the locore code to only use
  the bottom-most page of proc0stack for init386().  init386() returns
  the correct stack pointer to locore which adjusts the stack for thread0
  before calling mi_startup().
- Don't bother setting cr3 in thread0's pcb in locore before calling
  init386().  It wasn't used (init386() overwrote it at the end) and
  it doesn't work with the variable-sized FPU save area.
- Remove the new-bus attachment from npx.  This was only ever useful for
  external co-processors using IRQ13, but those have not been supported
  for several years.  npxinit() is now called much earlier during boot
  (init386()) similar to amd64.
- Implement PT_{GET,SET}XSTATE and I386_GET_XFPUSTATE.
- npxsave() is now only called from context switch contexts so it can
  use XSAVEOPT.

Differential Revision:	https://reviews.freebsd.org/D1058
Reviewed by:	kib
Tested on:	FreeBSD/i386 VM under bhyve on Intel i5-2520

1 files changed, 15 insertions, 0 deletions

diff --git a/sys/i386/i386/sys_machdep.c b/sys/i386/i386/sys_machdep.c
index 4245748efa4b..951886273107 100644
--- a/sys/i386/i386/sys_machdep.c
+++ b/sys/i386/i386/sys_machdep.c
@@ -105,6 +105,7 @@ sysarch(td, uap)
 	union {
 		struct i386_ldt_args largs;
 		struct i386_ioperm_args iargs;
+		struct i386_get_xfpustate xfpu;
 	} kargs;
 	uint32_t base;
 	struct segment_descriptor sd, *sdp;
@@ -126,6 +127,7 @@ sysarch(td, uap)
 		case I386_SET_FSBASE:
 		case I386_GET_GSBASE:
 		case I386_SET_GSBASE:
+		case I386_GET_XFPUSTATE:
 			break;
 
 		case I386_SET_IOPERM:
@@ -154,6 +156,11 @@ sysarch(td, uap)
 		if (kargs.largs.num > MAX_LD || kargs.largs.num <= 0)
 			return (EINVAL);
 		break;
+	case I386_GET_XFPUSTATE:
+		if ((error = copyin(uap->parms, &kargs.xfpu,
+		    sizeof(struct i386_get_xfpustate))) != 0)
+			return (error);
+		break;
 	default:
 		break;
 	}
@@ -270,6 +277,14 @@ sysarch(td, uap)
 			load_gs(GSEL(GUGS_SEL, SEL_UPL));
 		}
 		break;
+	case I386_GET_XFPUSTATE:
+		if (kargs.xfpu.len > cpu_max_ext_state_size -
+		    sizeof(union savefpu))
+			return (EINVAL);
+		npxgetregs(td);
+		error = copyout((char *)(get_pcb_user_save_td(td) + 1),
+		    kargs.xfpu.addr, kargs.xfpu.len);
+		break;
 	default:
 		error = EINVAL;
 		break;