Date: Sun, 25 Sep 2016 17:24:10 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r306314 - in stable/11: share/man/man9 sys/amd64/amd64 sys/amd64/include Message-ID: <201609251724.u8PHOA1e023990@repo.freebsd.org>
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Author: kib Date: Sun Sep 25 17:24:10 2016 New Revision: 306314 URL: https://svnweb.freebsd.org/changeset/base/306314 Log: MFC r305692: Add FPU_KERN_NOCTX flag to the fpu_kern_enter() function on amd64. Modified: stable/11/share/man/man9/fpu_kern.9 stable/11/sys/amd64/amd64/fpu.c stable/11/sys/amd64/include/fpu.h stable/11/sys/amd64/include/pcb.h Directory Properties: stable/11/ (props changed) Modified: stable/11/share/man/man9/fpu_kern.9 ============================================================================== --- stable/11/share/man/man9/fpu_kern.9 Sun Sep 25 16:50:31 2016 (r306313) +++ stable/11/share/man/man9/fpu_kern.9 Sun Sep 25 17:24:10 2016 (r306314) @@ -120,6 +120,16 @@ could be used from both kernel thread an The .Fn fpu_kern_leave function correctly handles such contexts. +.It Dv FPU_KERN_NOCTX +Avoid nesting save area. +If the flag is specified, the +.Fa ctx +must be passed as +.Va NULL . +The flag should only be used for really short code blocks +which can be executed in a critical section. +It avoids the need to allocate the FPU context by the cost +of increased system latency. .El .El .Pp Modified: stable/11/sys/amd64/amd64/fpu.c ============================================================================== --- stable/11/sys/amd64/amd64/fpu.c Sun Sep 25 16:50:31 2016 (r306313) +++ stable/11/sys/amd64/amd64/fpu.c Sun Sep 25 17:24:10 2016 (r306314) @@ -633,6 +633,8 @@ fpudna(void) */ critical_enter(); + KASSERT((curpcb->pcb_flags & PCB_FPUNOSAVE) == 0, + ("fpudna while in fpu_kern_enter(FPU_KERN_NOCTX)")); if (PCPU_GET(fpcurthread) == curthread) { printf("fpudna: fpcurthread == curthread\n"); stop_emulating(); @@ -964,13 +966,39 @@ fpu_kern_enter(struct thread *td, struct { 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_FPUNOSAVE) == 0, + ("recursive fpu_kern_enter while in PCB_FPUNOSAVE 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_FPUNOSAVE state is supposed to never need to + * save FPU context at all. + */ + fpurestore(fpu_initialstate); + set_pcb_flags(pcb, PCB_KERNFPU | PCB_FPUNOSAVE | + PCB_FPUINITDONE); + return (0); + } if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) { ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE; return (0); } - pcb = td->td_pcb; KASSERT(!PCB_USER_FPU(pcb) || pcb->pcb_save == get_pcb_user_save_pcb(pcb), ("mangled pcb_save")); ctx->flags = FPU_KERN_CTX_INUSE; @@ -989,19 +1017,34 @@ fpu_kern_leave(struct thread *td, struct { 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); - KASSERT((ctx->flags & FPU_KERN_CTX_DUMMY) == 0, ("dummy ctx")); pcb = td->td_pcb; - critical_enter(); - if (curthread == PCPU_GET(fpcurthread)) - fpudrop(); - critical_exit(); - pcb->pcb_save = ctx->prev; + + if ((pcb->pcb_flags & PCB_FPUNOSAVE) != 0) { + KASSERT(ctx == NULL, ("non-null ctx after FPU_KERN_NOCTX")); + KASSERT(PCPU_GET(fpcurthread) == NULL, + ("non-NULL fpcurthread for PCB_FPUNOSAVE")); + CRITICAL_ASSERT(td); + + clear_pcb_flags(pcb, PCB_FPUNOSAVE | PCB_FPUINITDONE); + start_emulating(); + critical_exit(); + } 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)) + fpudrop(); + critical_exit(); + pcb->pcb_save = ctx->prev; + } + if (pcb->pcb_save == get_pcb_user_save_pcb(pcb)) { if ((pcb->pcb_flags & PCB_USERFPUINITDONE) != 0) { set_pcb_flags(pcb, PCB_FPUINITDONE); Modified: stable/11/sys/amd64/include/fpu.h ============================================================================== --- stable/11/sys/amd64/include/fpu.h Sun Sep 25 16:50:31 2016 (r306313) +++ stable/11/sys/amd64/include/fpu.h Sun Sep 25 17:24:10 2016 (r306314) @@ -86,6 +86,7 @@ void fpu_save_area_reset(struct savefpu #define FPU_KERN_NORMAL 0x0000 #define FPU_KERN_NOWAIT 0x0001 #define FPU_KERN_KTHR 0x0002 +#define FPU_KERN_NOCTX 0x0004 #endif Modified: stable/11/sys/amd64/include/pcb.h ============================================================================== --- stable/11/sys/amd64/include/pcb.h Sun Sep 25 16:50:31 2016 (r306313) +++ stable/11/sys/amd64/include/pcb.h Sun Sep 25 17:24:10 2016 (r306314) @@ -83,6 +83,7 @@ struct pcb { #define PCB_FPUINITDONE 0x08 /* fpu state is initialized */ #define PCB_USERFPUINITDONE 0x10 /* fpu user state is initialized */ #define PCB_32BIT 0x40 /* process has 32 bit context (segs etc) */ +#define PCB_FPUNOSAVE 0x80 /* no save area for current FPU ctx */ uint16_t pcb_initial_fpucw;
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