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Add support for FPU_KERN_NOCTX.

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This mirrors the implementation on amd64.

Reviewed by:	kib
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D26754
This commit is contained in:
John Baldwin 2020-10-13 17:27:37 +00:00
parent 4ef6ea38fc
commit 1775215f88
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=366673
3 changed files with 57 additions and 11 deletions
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66
sys/i386/i386/npx.c
View File

@ -886,6 +886,9 @@ npxdna(void)
return (0);
td = curthread;
critical_enter();
KASSERT((curpcb->pcb_flags & PCB_NPXNOSAVE) == 0,
("npxdna while in fpu_kern_enter(FPU_KERN_NOCTX)"));
if (__predict_false(PCPU_GET(fpcurthread) == td)) {
/*
* Some virtual machines seems to set %cr0.TS at
@ -1390,8 +1393,34 @@ fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
struct pcb *pcb;
KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) == 0, ("using inuse ctx"));
pcb = td->td_pcb;
KASSERT((flags & FPU_KERN_NOCTX) != 0 || ctx != NULL,
("ctx is required when !FPU_KERN_NOCTX"));
KASSERT(ctx == NULL || (ctx->flags & FPU_KERN_CTX_INUSE) == 0,
("using inuse ctx"));
KASSERT((pcb->pcb_flags & PCB_NPXNOSAVE) == 0,
("recursive fpu_kern_enter while in PCB_NPXNOSAVE state"));
if ((flags & FPU_KERN_NOCTX) != 0) {
critical_enter();
stop_emulating();
if (curthread == PCPU_GET(fpcurthread)) {
fpusave(curpcb->pcb_save);
PCPU_SET(fpcurthread, NULL);
} else {
KASSERT(PCPU_GET(fpcurthread) == NULL,
("invalid fpcurthread"));
}
/*
* This breaks XSAVEOPT tracker, but
* PCB_NPXNOSAVE state is supposed to never need to
* save FPU context at all.
*/
fpurstor(npx_initialstate);
pcb->pcb_flags |= PCB_KERNNPX | PCB_NPXNOSAVE | PCB_NPXINITDONE;
return;
}
if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) {
ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE;
return;
@ -1416,17 +1445,32 @@ fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
{
struct pcb *pcb;
KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) != 0,
("leaving not inuse ctx"));
ctx->flags &= ~FPU_KERN_CTX_INUSE;
if (is_fpu_kern_thread(0) && (ctx->flags & FPU_KERN_CTX_DUMMY) != 0)
return (0);
pcb = td->td_pcb;
critical_enter();
if (curthread == PCPU_GET(fpcurthread))
npxdrop();
pcb->pcb_save = ctx->prev;
if ((pcb->pcb_flags & PCB_NPXNOSAVE) != 0) {
KASSERT(ctx == NULL, ("non-null ctx after FPU_KERN_NOCTX"));
KASSERT(PCPU_GET(fpcurthread) == NULL,
("non-NULL fpcurthread for PCB_NPXNOSAVE"));
CRITICAL_ASSERT(td);
pcb->pcb_flags &= ~(PCB_NPXNOSAVE | PCB_NPXINITDONE);
start_emulating();
} else {
KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) != 0,
("leaving not inuse ctx"));
ctx->flags &= ~FPU_KERN_CTX_INUSE;
if (is_fpu_kern_thread(0) &&
(ctx->flags & FPU_KERN_CTX_DUMMY) != 0)
return (0);
KASSERT((ctx->flags & FPU_KERN_CTX_DUMMY) == 0,
("dummy ctx"));
critical_enter();
if (curthread == PCPU_GET(fpcurthread))
npxdrop();
pcb->pcb_save = ctx->prev;
}
if (pcb->pcb_save == get_pcb_user_save_pcb(pcb)) {
if ((pcb->pcb_flags & PCB_NPXUSERINITDONE) != 0)
pcb->pcb_flags |= PCB_NPXINITDONE;

1
sys/i386/include/npx.h
View File

@ -92,6 +92,7 @@ void fpu_save_area_reset(union savefpu *fsa);
#define FPU_KERN_NORMAL 0x0000
#define FPU_KERN_NOWAIT 0x0001
#define FPU_KERN_KTHR 0x0002
#define FPU_KERN_NOCTX 0x0004
#endif

1
sys/i386/include/pcb.h
View File

@ -86,6 +86,7 @@ struct pcb {
#define PCB_VM86CALL 0x10 /* in vm86 call */
#define PCB_NPXUSERINITDONE 0x20 /* user fpu state is initialized */
#define PCB_KERNNPX 0x40 /* kernel uses npx */
#define PCB_NPXNOSAVE 0x80 /* no save area for current FPU ctx */
uint16_t pcb_initial_npxcw;