IFC @r269962

[FreeBSD/FreeBSD.git] / sys / i386 / i386 / vm_machdep.c

/*-
 * Copyright (c) 1982, 1986 The Regents of the University of California.
 * Copyright (c) 1989, 1990 William Jolitz
 * Copyright (c) 1994 John Dyson
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department, and William Jolitz.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
 *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_isa.h"
#include "opt_npx.h"
#include "opt_reset.h"
#include "opt_cpu.h"
#include "opt_xbox.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/pioctl.h>
#include <sys/proc.h>
#include <sys/sysent.h>
#include <sys/sf_buf.h>
#include <sys/smp.h>
#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>

#include <machine/cpu.h>
#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/pcb_ext.h>
#include <machine/smp.h>
#include <machine/vm86.h>

#ifdef CPU_ELAN
#include <machine/elan_mmcr.h>
#endif

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_param.h>

#ifdef XEN
#include <xen/hypervisor.h>
#endif
#ifdef PC98
#include <pc98/cbus/cbus.h>
#else
#include <isa/isareg.h>
#endif

#ifdef XBOX
#include <machine/xbox.h>
#endif

#ifndef NSFBUFS
#define NSFBUFS         (512 + maxusers * 16)
#endif

_Static_assert(OFFSETOF_CURTHREAD == offsetof(struct pcpu, pc_curthread),
    "OFFSETOF_CURTHREAD does not correspond with offset of pc_curthread.");
_Static_assert(OFFSETOF_CURPCB == offsetof(struct pcpu, pc_curpcb),
    "OFFSETOF_CURPCB does not correspond with offset of pc_curpcb.");

static void     cpu_reset_real(void);
#ifdef SMP
static void     cpu_reset_proxy(void);
static u_int    cpu_reset_proxyid;
static volatile u_int   cpu_reset_proxy_active;
#endif

extern int      _ucodesel, _udatasel;

/*
 * Finish a fork operation, with process p2 nearly set up.
 * Copy and update the pcb, set up the stack so that the child
 * ready to run and return to user mode.
 */
void
cpu_fork(td1, p2, td2, flags)
        register struct thread *td1;
        register struct proc *p2;
        struct thread *td2;
        int flags;
{
        register struct proc *p1;
        struct pcb *pcb2;
        struct mdproc *mdp2;

        p1 = td1->td_proc;
        if ((flags & RFPROC) == 0) {
                if ((flags & RFMEM) == 0) {
                        /* unshare user LDT */
                        struct mdproc *mdp1 = &p1->p_md;
                        struct proc_ldt *pldt, *pldt1;

                        mtx_lock_spin(&dt_lock);
                        if ((pldt1 = mdp1->md_ldt) != NULL &&
                            pldt1->ldt_refcnt > 1) {
                                pldt = user_ldt_alloc(mdp1, pldt1->ldt_len);
                                if (pldt == NULL)
                                        panic("could not copy LDT");
                                mdp1->md_ldt = pldt;
                                set_user_ldt(mdp1);
                                user_ldt_deref(pldt1);
                        } else
                                mtx_unlock_spin(&dt_lock);
                }
                return;
        }

        /* Ensure that td1's pcb is up to date. */
        if (td1 == curthread)
                td1->td_pcb->pcb_gs = rgs();
#ifdef DEV_NPX
        critical_enter();
        if (PCPU_GET(fpcurthread) == td1)
                npxsave(td1->td_pcb->pcb_save);
        critical_exit();
#endif

        /* Point the pcb to the top of the stack */
        pcb2 = (struct pcb *)(td2->td_kstack +
            td2->td_kstack_pages * PAGE_SIZE) - 1;
        td2->td_pcb = pcb2;

        /* Copy td1's pcb */
        bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));

        /* Properly initialize pcb_save */
        pcb2->pcb_save = &pcb2->pcb_user_save;

        /* Point mdproc and then copy over td1's contents */
        mdp2 = &p2->p_md;
        bcopy(&p1->p_md, mdp2, sizeof(*mdp2));

        /*
         * Create a new fresh stack for the new process.
         * Copy the trap frame for the return to user mode as if from a
         * syscall.  This copies most of the user mode register values.
         * The -16 is so we can expand the trapframe if we go to vm86.
         */
        td2->td_frame = (struct trapframe *)((caddr_t)td2->td_pcb - 16) - 1;
        bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));

        td2->td_frame->tf_eax = 0;              /* Child returns zero */
        td2->td_frame->tf_eflags &= ~PSL_C;     /* success */
        td2->td_frame->tf_edx = 1;

        /*
         * If the parent process has the trap bit set (i.e. a debugger had
         * single stepped the process to the system call), we need to clear
         * the trap flag from the new frame unless the debugger had set PF_FORK
         * on the parent.  Otherwise, the child will receive a (likely
         * unexpected) SIGTRAP when it executes the first instruction after
         * returning  to userland.
         */
        if ((p1->p_pfsflags & PF_FORK) == 0)
                td2->td_frame->tf_eflags &= ~PSL_T;

        /*
         * Set registers for trampoline to user mode.  Leave space for the
         * return address on stack.  These are the kernel mode register values.
         */
#ifdef PAE
        pcb2->pcb_cr3 = vtophys(vmspace_pmap(p2->p_vmspace)->pm_pdpt);
#else
        pcb2->pcb_cr3 = vtophys(vmspace_pmap(p2->p_vmspace)->pm_pdir);
#endif
        pcb2->pcb_edi = 0;
        pcb2->pcb_esi = (int)fork_return;       /* fork_trampoline argument */
        pcb2->pcb_ebp = 0;
        pcb2->pcb_esp = (int)td2->td_frame - sizeof(void *);
        pcb2->pcb_ebx = (int)td2;               /* fork_trampoline argument */
        pcb2->pcb_eip = (int)fork_trampoline;
        pcb2->pcb_psl = PSL_KERNEL;             /* ints disabled */
        /*-
         * pcb2->pcb_dr*:       cloned above.
         * pcb2->pcb_savefpu:   cloned above.
         * pcb2->pcb_flags:     cloned above.
         * pcb2->pcb_onfault:   cloned above (always NULL here?).
         * pcb2->pcb_gs:        cloned above.
         * pcb2->pcb_ext:       cleared below.
         */

        /*
         * XXX don't copy the i/o pages.  this should probably be fixed.
         */
        pcb2->pcb_ext = 0;

        /* Copy the LDT, if necessary. */
        mtx_lock_spin(&dt_lock);
        if (mdp2->md_ldt != NULL) {
                if (flags & RFMEM) {
                        mdp2->md_ldt->ldt_refcnt++;
                } else {
                        mdp2->md_ldt = user_ldt_alloc(mdp2,
                            mdp2->md_ldt->ldt_len);
                        if (mdp2->md_ldt == NULL)
                                panic("could not copy LDT");
                }
        }
        mtx_unlock_spin(&dt_lock);

        /* Setup to release spin count in fork_exit(). */
        td2->td_md.md_spinlock_count = 1;
        /*
         * XXX XEN need to check on PSL_USER is handled
         */
        td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
        /*
         * Now, cpu_switch() can schedule the new process.
         * pcb_esp is loaded pointing to the cpu_switch() stack frame
         * containing the return address when exiting cpu_switch.
         * This will normally be to fork_trampoline(), which will have
         * %ebx loaded with the new proc's pointer.  fork_trampoline()
         * will set up a stack to call fork_return(p, frame); to complete
         * the return to user-mode.
         */
}

/*
 * Intercept the return address from a freshly forked process that has NOT
 * been scheduled yet.
 *
 * This is needed to make kernel threads stay in kernel mode.
 */
void
cpu_set_fork_handler(td, func, arg)
        struct thread *td;
        void (*func)(void *);
        void *arg;
{
        /*
         * Note that the trap frame follows the args, so the function
         * is really called like this:  func(arg, frame);
         */
        td->td_pcb->pcb_esi = (int) func;       /* function */
        td->td_pcb->pcb_ebx = (int) arg;        /* first arg */
}

void
cpu_exit(struct thread *td)
{

        /*
         * If this process has a custom LDT, release it.  Reset pc->pcb_gs
         * and %gs before we free it in case they refer to an LDT entry.
         */
        mtx_lock_spin(&dt_lock);
        if (td->td_proc->p_md.md_ldt) {
                td->td_pcb->pcb_gs = _udatasel;
                load_gs(_udatasel);
                user_ldt_free(td);
        } else
                mtx_unlock_spin(&dt_lock);
}

void
cpu_thread_exit(struct thread *td)
{

#ifdef DEV_NPX
        critical_enter();
        if (td == PCPU_GET(fpcurthread))
                npxdrop();
        critical_exit();
#endif

        /* Disable any hardware breakpoints. */
        if (td->td_pcb->pcb_flags & PCB_DBREGS) {
                reset_dbregs();
                td->td_pcb->pcb_flags &= ~PCB_DBREGS;
        }
}

void
cpu_thread_clean(struct thread *td)
{
        struct pcb *pcb;

        pcb = td->td_pcb; 
        if (pcb->pcb_ext != NULL) {
                /* if (pcb->pcb_ext->ext_refcount-- == 1) ?? */
                /*
                 * XXX do we need to move the TSS off the allocated pages
                 * before freeing them?  (not done here)
                 */
                kmem_free(kernel_arena, (vm_offset_t)pcb->pcb_ext,
                    ctob(IOPAGES + 1));
                pcb->pcb_ext = NULL;
        }
}

void
cpu_thread_swapin(struct thread *td)
{
}

void
cpu_thread_swapout(struct thread *td)
{
}

void
cpu_thread_alloc(struct thread *td)
{

        td->td_pcb = (struct pcb *)(td->td_kstack +
            td->td_kstack_pages * PAGE_SIZE) - 1;
        td->td_frame = (struct trapframe *)((caddr_t)td->td_pcb - 16) - 1;
        td->td_pcb->pcb_ext = NULL; 
        td->td_pcb->pcb_save = &td->td_pcb->pcb_user_save;
}

void
cpu_thread_free(struct thread *td)
{

        cpu_thread_clean(td);
}

void
cpu_set_syscall_retval(struct thread *td, int error)
{

        switch (error) {
        case 0:
                td->td_frame->tf_eax = td->td_retval[0];
                td->td_frame->tf_edx = td->td_retval[1];
                td->td_frame->tf_eflags &= ~PSL_C;
                break;

        case ERESTART:
                /*
                 * Reconstruct pc, assuming lcall $X,y is 7 bytes, int
                 * 0x80 is 2 bytes. We saved this in tf_err.
                 */
                td->td_frame->tf_eip -= td->td_frame->tf_err;
                break;

        case EJUSTRETURN:
                break;

        default:
                if (td->td_proc->p_sysent->sv_errsize) {
                        if (error >= td->td_proc->p_sysent->sv_errsize)
                                error = -1;     /* XXX */
                        else
                                error = td->td_proc->p_sysent->sv_errtbl[error];
                }
                td->td_frame->tf_eax = error;
                td->td_frame->tf_eflags |= PSL_C;
                break;
        }
}

/*
 * Initialize machine state (pcb and trap frame) for a new thread about to
 * upcall. Put enough state in the new thread's PCB to get it to go back 
 * userret(), where we can intercept it again to set the return (upcall)
 * Address and stack, along with those from upcals that are from other sources
 * such as those generated in thread_userret() itself.
 */
void
cpu_set_upcall(struct thread *td, struct thread *td0)
{
        struct pcb *pcb2;

        /* Point the pcb to the top of the stack. */
        pcb2 = td->td_pcb;

        /*
         * Copy the upcall pcb.  This loads kernel regs.
         * Those not loaded individually below get their default
         * values here.
         */
        bcopy(td0->td_pcb, pcb2, sizeof(*pcb2));
        pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE |
            PCB_KERNNPX);
        pcb2->pcb_save = &pcb2->pcb_user_save;

        /*
         * Create a new fresh stack for the new thread.
         */
        bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe));

        /* If the current thread has the trap bit set (i.e. a debugger had
         * single stepped the process to the system call), we need to clear
         * the trap flag from the new frame. Otherwise, the new thread will
         * receive a (likely unexpected) SIGTRAP when it executes the first
         * instruction after returning to userland.
         */
        td->td_frame->tf_eflags &= ~PSL_T;

        /*
         * Set registers for trampoline to user mode.  Leave space for the
         * return address on stack.  These are the kernel mode register values.
         */
        pcb2->pcb_edi = 0;
        pcb2->pcb_esi = (int)fork_return;                   /* trampoline arg */
        pcb2->pcb_ebp = 0;
        pcb2->pcb_esp = (int)td->td_frame - sizeof(void *); /* trampoline arg */
        pcb2->pcb_ebx = (int)td;                            /* trampoline arg */
        pcb2->pcb_eip = (int)fork_trampoline;
        pcb2->pcb_psl &= ~(PSL_I);      /* interrupts must be disabled */
        pcb2->pcb_gs = rgs();
        /*
         * If we didn't copy the pcb, we'd need to do the following registers:
         * pcb2->pcb_cr3:       cloned above.
         * pcb2->pcb_dr*:       cloned above.
         * pcb2->pcb_savefpu:   cloned above.
         * pcb2->pcb_flags:     cloned above.
         * pcb2->pcb_onfault:   cloned above (always NULL here?).
         * pcb2->pcb_gs:        cloned above.
         * pcb2->pcb_ext:       cleared below.
         */
        pcb2->pcb_ext = NULL;

        /* Setup to release spin count in fork_exit(). */
        td->td_md.md_spinlock_count = 1;
        td->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
}

/*
 * Set that machine state for performing an upcall that has to
 * be done in thread_userret() so that those upcalls generated
 * in thread_userret() itself can be done as well.
 */
void
cpu_set_upcall_kse(struct thread *td, void (*entry)(void *), void *arg,
        stack_t *stack)
{

        /* 
         * Do any extra cleaning that needs to be done.
         * The thread may have optional components
         * that are not present in a fresh thread.
         * This may be a recycled thread so make it look
         * as though it's newly allocated.
         */
        cpu_thread_clean(td);

        /*
         * Set the trap frame to point at the beginning of the uts
         * function.
         */
        td->td_frame->tf_ebp = 0; 
        td->td_frame->tf_esp =
            (((int)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4;
        td->td_frame->tf_eip = (int)entry;

        /*
         * Pass the address of the mailbox for this kse to the uts
         * function as a parameter on the stack.
         */
        suword((void *)(td->td_frame->tf_esp + sizeof(void *)),
            (int)arg);
}

int
cpu_set_user_tls(struct thread *td, void *tls_base)
{
        struct segment_descriptor sd;
        uint32_t base;

        /*
         * Construct a descriptor and store it in the pcb for
         * the next context switch.  Also store it in the gdt
         * so that the load of tf_fs into %fs will activate it
         * at return to userland.
         */
        base = (uint32_t)tls_base;
        sd.sd_lobase = base & 0xffffff;
        sd.sd_hibase = (base >> 24) & 0xff;
        sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */
        sd.sd_hilimit = 0xf;
        sd.sd_type  = SDT_MEMRWA;
        sd.sd_dpl   = SEL_UPL;
        sd.sd_p     = 1;
        sd.sd_xx    = 0;
        sd.sd_def32 = 1;
        sd.sd_gran  = 1;
        critical_enter();
        /* set %gs */
        td->td_pcb->pcb_gsd = sd;
        if (td == curthread) {
                PCPU_GET(fsgs_gdt)[1] = sd;
                load_gs(GSEL(GUGS_SEL, SEL_UPL));
        }
        critical_exit();
        return (0);
}

/*
 * Convert kernel VA to physical address
 */
vm_paddr_t
kvtop(void *addr)
{
        vm_paddr_t pa;

        pa = pmap_kextract((vm_offset_t)addr);
        if (pa == 0)
                panic("kvtop: zero page frame");
        return (pa);
}

#ifdef SMP
static void
cpu_reset_proxy()
{
        cpuset_t tcrp;

        cpu_reset_proxy_active = 1;
        while (cpu_reset_proxy_active == 1)
                ;       /* Wait for other cpu to see that we've started */
        CPU_SETOF(cpu_reset_proxyid, &tcrp);
        stop_cpus(tcrp);
        printf("cpu_reset_proxy: Stopped CPU %d\n", cpu_reset_proxyid);
        DELAY(1000000);
        cpu_reset_real();
}
#endif

void
cpu_reset()
{
#ifdef XBOX
        if (arch_i386_is_xbox) {
                /* Kick the PIC16L, it can reboot the box */
                pic16l_reboot();
                for (;;);
        }
#endif

#ifdef SMP
        cpuset_t map;
        u_int cnt;

        if (smp_started) {
                map = all_cpus;
                CPU_CLR(PCPU_GET(cpuid), &map);
                CPU_NAND(&map, &stopped_cpus);
                if (!CPU_EMPTY(&map)) {
                        printf("cpu_reset: Stopping other CPUs\n");
                        stop_cpus(map);
                }

                if (PCPU_GET(cpuid) != 0) {
                        cpu_reset_proxyid = PCPU_GET(cpuid);
                        cpustop_restartfunc = cpu_reset_proxy;
                        cpu_reset_proxy_active = 0;
                        printf("cpu_reset: Restarting BSP\n");

                        /* Restart CPU #0. */
                        /* XXX: restart_cpus(1 << 0); */
                        CPU_SETOF(0, &started_cpus);
                        wmb();

                        cnt = 0;
                        while (cpu_reset_proxy_active == 0 && cnt < 10000000)
                                cnt++;  /* Wait for BSP to announce restart */
                        if (cpu_reset_proxy_active == 0)
                                printf("cpu_reset: Failed to restart BSP\n");
                        enable_intr();
                        cpu_reset_proxy_active = 2;

                        while (1);
                        /* NOTREACHED */
                }

                DELAY(1000000);
        }
#endif
        cpu_reset_real();
        /* NOTREACHED */
}

static void
cpu_reset_real()
{
        struct region_descriptor null_idt;
#ifndef PC98
        int b;
#endif

        disable_intr();
#ifdef XEN
        if (smp_processor_id() == 0)
                HYPERVISOR_shutdown(SHUTDOWN_reboot);
        else
                HYPERVISOR_shutdown(SHUTDOWN_poweroff);
#endif 
#ifdef CPU_ELAN
        if (elan_mmcr != NULL)
                elan_mmcr->RESCFG = 1;
#endif

        if (cpu == CPU_GEODE1100) {
                /* Attempt Geode's own reset */
                outl(0xcf8, 0x80009044ul);
                outl(0xcfc, 0xf);
        }

#ifdef PC98
        /*
         * Attempt to do a CPU reset via CPU reset port.
         */
        if ((inb(0x35) & 0xa0) != 0xa0) {
                outb(0x37, 0x0f);               /* SHUT0 = 0. */
                outb(0x37, 0x0b);               /* SHUT1 = 0. */
        }
        outb(0xf0, 0x00);               /* Reset. */
#else
#if !defined(BROKEN_KEYBOARD_RESET)
        /*
         * Attempt to do a CPU reset via the keyboard controller,
         * do not turn off GateA20, as any machine that fails
         * to do the reset here would then end up in no man's land.
         */
        outb(IO_KBD + 4, 0xFE);
        DELAY(500000);  /* wait 0.5 sec to see if that did it */
#endif

        /*
         * Attempt to force a reset via the Reset Control register at
         * I/O port 0xcf9.  Bit 2 forces a system reset when it
         * transitions from 0 to 1.  Bit 1 selects the type of reset
         * to attempt: 0 selects a "soft" reset, and 1 selects a
         * "hard" reset.  We try a "hard" reset.  The first write sets
         * bit 1 to select a "hard" reset and clears bit 2.  The
         * second write forces a 0 -> 1 transition in bit 2 to trigger
         * a reset.
         */
        outb(0xcf9, 0x2);
        outb(0xcf9, 0x6);
        DELAY(500000);  /* wait 0.5 sec to see if that did it */

        /*
         * Attempt to force a reset via the Fast A20 and Init register
         * at I/O port 0x92.  Bit 1 serves as an alternate A20 gate.
         * Bit 0 asserts INIT# when set to 1.  We are careful to only
         * preserve bit 1 while setting bit 0.  We also must clear bit
         * 0 before setting it if it isn't already clear.
         */
        b = inb(0x92);
        if (b != 0xff) {
                if ((b & 0x1) != 0)
                        outb(0x92, b & 0xfe);
                outb(0x92, b | 0x1);
                DELAY(500000);  /* wait 0.5 sec to see if that did it */
        }
#endif /* PC98 */

        printf("No known reset method worked, attempting CPU shutdown\n");
        DELAY(1000000); /* wait 1 sec for printf to complete */

        /* Wipe the IDT. */
        null_idt.rd_limit = 0;
        null_idt.rd_base = 0;
        lidt(&null_idt);

        /* "good night, sweet prince .... <THUNK!>" */
        breakpoint();

        /* NOTREACHED */
        while(1);
}

/*
 * Get an sf_buf from the freelist.  May block if none are available.
 */
void
sf_buf_map(struct sf_buf *sf, int flags)
{
        pt_entry_t opte, *ptep;

        /*
         * Update the sf_buf's virtual-to-physical mapping, flushing the
         * virtual address from the TLB.  Since the reference count for 
         * the sf_buf's old mapping was zero, that mapping is not 
         * currently in use.  Consequently, there is no need to exchange 
         * the old and new PTEs atomically, even under PAE.
         */
        ptep = vtopte(sf->kva);
        opte = *ptep;
#ifdef XEN
       PT_SET_MA(sf->kva, xpmap_ptom(VM_PAGE_TO_PHYS(sf->m)) | pgeflag
           | PG_RW | PG_V | pmap_cache_bits(sf->m->md.pat_mode, 0));
#else
        *ptep = VM_PAGE_TO_PHYS(sf->m) | pgeflag | PG_RW | PG_V |
            pmap_cache_bits(sf->m->md.pat_mode, 0);
#endif

        /*
         * Avoid unnecessary TLB invalidations: If the sf_buf's old
         * virtual-to-physical mapping was not used, then any processor
         * that has invalidated the sf_buf's virtual address from its TLB
         * since the last used mapping need not invalidate again.
         */
#ifdef SMP
        if ((opte & (PG_V | PG_A)) ==  (PG_V | PG_A))
                CPU_ZERO(&sf->cpumask);

        sf_buf_shootdown(sf, flags);
#else
        if ((opte & (PG_V | PG_A)) ==  (PG_V | PG_A))
                pmap_invalidate_page(kernel_pmap, sf->kva);
#endif
}

#ifdef SMP
void
sf_buf_shootdown(struct sf_buf *sf, int flags)
{
        cpuset_t other_cpus;
        u_int cpuid;

        sched_pin();
        cpuid = PCPU_GET(cpuid);
        if (!CPU_ISSET(cpuid, &sf->cpumask)) {
                CPU_SET(cpuid, &sf->cpumask);
                invlpg(sf->kva);
        }
        if ((flags & SFB_CPUPRIVATE) == 0) {
                other_cpus = all_cpus;
                CPU_CLR(cpuid, &other_cpus);
                CPU_NAND(&other_cpus, &sf->cpumask);
                if (!CPU_EMPTY(&other_cpus)) {
                        CPU_OR(&sf->cpumask, &other_cpus);
                        smp_masked_invlpg(other_cpus, sf->kva);
                }
        }
        sched_unpin();
}
#endif

/*
 * MD part of sf_buf_free().
 */
int
sf_buf_unmap(struct sf_buf *sf)
{
#ifdef XEN
        /*
         * Xen doesn't like having dangling R/W mappings
         */
        pmap_qremove(sf->kva, 1);
        return (1);
#else
        return (0);
#endif
}

static void
sf_buf_invalidate(struct sf_buf *sf)
{
        vm_page_t m = sf->m;

        /*
         * Use pmap_qenter to update the pte for
         * existing mapping, in particular, the PAT
         * settings are recalculated.
         */
        pmap_qenter(sf->kva, &m, 1);
        pmap_invalidate_cache_range(sf->kva, sf->kva + PAGE_SIZE);
}

/*
 * Invalidate the cache lines that may belong to the page, if
 * (possibly old) mapping of the page by sf buffer exists.  Returns
 * TRUE when mapping was found and cache invalidated.
 */
boolean_t
sf_buf_invalidate_cache(vm_page_t m)
{

        return (sf_buf_process_page(m, sf_buf_invalidate));
}

/*
 * Software interrupt handler for queued VM system processing.
 */   
void  
swi_vm(void *dummy) 
{     
        if (busdma_swi_pending != 0)
                busdma_swi();
}

/*
 * Tell whether this address is in some physical memory region.
 * Currently used by the kernel coredump code in order to avoid
 * dumping the ``ISA memory hole'' which could cause indefinite hangs,
 * or other unpredictable behaviour.
 */

int
is_physical_memory(vm_paddr_t addr)
{

#ifdef DEV_ISA
        /* The ISA ``memory hole''. */
        if (addr >= 0xa0000 && addr < 0x100000)
                return 0;
#endif

        /*
         * stuff other tests for known memory-mapped devices (PCI?)
         * here
         */

        return 1;
}