kernel: introduce per process FPU struct (PFPU) for more flexible machine specific fpu handling

introducing the PFPU structue which allows the machine specific
code some flexibility on how to handle the FPU process state.

for example, in the pc and pc64 kernel, the FPsave structure is
arround 512 bytes. with avx512, it could grow up to 2K. instead
of embedding that into the Proc strucutre, it is more effective
to allocate it on first use of the fpu, as most processes do not
use simd or floating point in the first place. also, the FPsave
structure has special 16 byte alignment constraint, which further
favours dynamic allocation.

this gets rid of the memmoves in pc/pc64 kernels for the aligment.

there is also devproc, which is now checking if the fpsave area
is actually valid before reading it, avoiding debuggers to see
garbage data.

the Notsave structure is gone now, as it was not used on any
machine.

1 files changed, 16 insertions, 42 deletions

diff --git a/sys/src/9/pc/main.c b/sys/src/9/pc/main.c
index 5408e6982..6dbf76a3e 100644
--- a/sys/src/9/pc/main.c
+++ b/sys/src/9/pc/main.c
@@ -311,12 +311,8 @@ confinit(void)
 }
 
 /*
- * we keep FPsave structure in sse format emulating FXSAVE / FXRSTOR
+ * we keep FPsave structure in SSE format emulating FXSAVE / FXRSTOR
  * instructions for legacy x87 fpu.
- *
- * Note that fpx87restore() and fpxsserestore() do modify the FPsave
- * data structure for conversion / realignment shuffeling. this means
- * that p->fpsave is only valid when p->fpstate == FPinactive.
  */
 void
 fpx87save(FPsave *fps)
@@ -441,32 +437,6 @@ fpx87restore(FPsave *fps)
 	fpx87restore0(fps);
 }
 
-/*
- * sse fp save and restore buffers have to be 16-byte (FPalign) aligned,
- * so we shuffle the data up and down as needed or make copies.
- */
-void
-fpssesave(FPsave *fps)
-{
-	FPsave *afps;
-
-	afps = (FPsave *)ROUND(((uintptr)fps), FPalign);
-	fpssesave0(afps);
-	if(fps != afps)  /* not aligned? shuffle down from aligned buffer */
-		memmove(fps, afps, sizeof(FPssestate) - FPalign);
-}
-
-void
-fpsserestore(FPsave *fps)
-{
-	FPsave *afps;
-
-	afps = (FPsave *)ROUND(((uintptr)fps), FPalign);
-	if(fps != afps)  /* shuffle up to make aligned */
-		memmove(afps, fps, sizeof(FPssestate) - FPalign);
-	fpsserestore0(afps);
-}
-
 static char* mathmsg[] =
 {
 	nil,	/* handled below */
@@ -524,9 +494,9 @@ matherror(Ureg*, void*)
 	/*
 	 *  get floating point state to check out error
 	 */
-	fpsave(&up->fpsave);
+	fpsave(up->fpsave);
 	up->fpstate = FPinactive;
-	mathnote(up->fpsave.fsw, up->fpsave.fpuip);
+	mathnote(up->fpsave->fsw, up->fpsave->fpuip);
 }
 
 /*
@@ -535,9 +505,9 @@ matherror(Ureg*, void*)
 static void
 simderror(Ureg *ureg, void*)
 {
-	fpsave(&up->fpsave);
+	fpsave(up->fpsave);
 	up->fpstate = FPinactive;
-	mathnote(up->fpsave.mxcsr & 0x3f, ureg->pc);
+	mathnote(up->fpsave->mxcsr & 0x3f, ureg->pc);
 }
 
 /*
@@ -558,6 +528,8 @@ mathemu(Ureg *ureg, void*)
 		fpinit();
 		if(fpsave == fpssesave)
 			ldmxcsr(0);	/* no simd exceptions on 386 */
+		while(up->fpsave == nil)
+			up->fpsave = mallocalign(sizeof(FPsave), FPalign, 0, 0);
 		up->fpstate = FPactive;
 		break;
 	case FPinactive:
@@ -568,13 +540,13 @@ mathemu(Ureg *ureg, void*)
 		 * More attention should probably be paid here to the
 		 * exception masks and error summary.
 		 */
-		status = up->fpsave.fsw;
-		control = up->fpsave.fcw;
+		status = up->fpsave->fsw;
+		control = up->fpsave->fcw;
 		if((status & ~control) & 0x07F){
-			mathnote(status, up->fpsave.fpuip);
+			mathnote(status, up->fpsave->fpuip);
 			break;
 		}
-		fprestore(&up->fpsave);
+		fprestore(up->fpsave);
 		up->fpstate = FPactive;
 		break;
 	case FPactive:
@@ -645,10 +617,12 @@ procfork(Proc *p)
 	s = splhi();
 	switch(up->fpstate & ~FPillegal){
 	case FPactive:
-		fpsave(&up->fpsave);
+		fpsave(up->fpsave);
 		up->fpstate = FPinactive;
 	case FPinactive:
-		p->fpsave = up->fpsave;
+		while(p->fpsave == nil)
+			p->fpsave = mallocalign(sizeof(FPsave), FPalign, 0, 0);
+		memmove(p->fpsave, up->fpsave, sizeof(FPsave));
 		p->fpstate = FPinactive;
 	}
 	
@@ -708,7 +682,7 @@ procsave(Proc *p)
 			 * until the process runs again and generates an
 			 * emulation fault to activate the FPU.
 			 */
-			fpsave(&p->fpsave);
+			fpsave(p->fpsave);
 		}
 		p->fpstate = FPinactive;
 	}