paravirt.c

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/*  Paravirtualization interfaces
    Copyright (C) 2006 Rusty Russell IBM Corporation

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    2007 - x86_64 support added by Glauber de Oliveira Costa, Red Hat Inc
*/

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/efi.h>
#include <linux/bcd.h>
#include <linux/highmem.h>

#include <asm/bug.h>
#include <asm/paravirt.h>
#include <asm/debugreg.h>
#include <asm/desc.h>
#include <asm/setup.h>
#include <asm/pgtable.h>
#include <asm/time.h>
#include <asm/pgalloc.h>
#include <asm/irq.h>
#include <asm/delay.h>
#include <asm/fixmap.h>
#include <asm/apic.h>
#include <asm/tlbflush.h>
#include <asm/timer.h>
#include <asm/special_insns.h>

/* nop stub */
void _paravirt_nop(void)
{
}

/* identity function, which can be inlined */
u32 _paravirt_ident_32(u32 x)
{
    return x;
}

u64 _paravirt_ident_64(u64 x)
{
    return x;
}

void __init default_banner(void)
{
    printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
           pv_info.name);
}

/* Simple instruction patching code. */
#define DEF_NATIVE(ops, name, code)                 \
    extern const char start_##ops##_##name[], end_##ops##_##name[]; \
    asm("start_" #ops "_" #name ": " code "; end_" #ops "_" #name ":")

/* Undefined instruction for dealing with missing ops pointers. */
static const unsigned char ud2a[] = { 0x0f, 0x0b };

unsigned paravirt_patch_nop(void)
{
    return 0;
}

unsigned paravirt_patch_ignore(unsigned len)
{
    return len;
}

struct branch {
    unsigned char opcode;
    u32 delta;
} __attribute__((packed));

unsigned paravirt_patch_call(void *insnbuf,
                 const void *target, u16 tgt_clobbers,
                 unsigned long addr, u16 site_clobbers,
                 unsigned len)
{
    struct branch *b = insnbuf;
    unsigned long delta = (unsigned long)target - (addr+5);

    if (tgt_clobbers & ~site_clobbers)
        return len; /* target would clobber too much for this site */
    if (len < 5)
        return len; /* call too long for patch site */

    b->opcode = 0xe8; /* call */
    b->delta = delta;
    BUILD_BUG_ON(sizeof(*b) != 5);

    return 5;
}

unsigned paravirt_patch_jmp(void *insnbuf, const void *target,
                unsigned long addr, unsigned len)
{
    struct branch *b = insnbuf;
    unsigned long delta = (unsigned long)target - (addr+5);

    if (len < 5)
        return len; /* call too long for patch site */

    b->opcode = 0xe9;   /* jmp */
    b->delta = delta;

    return 5;
}

/* Neat trick to map patch type back to the call within the
 * corresponding structure. */
static void *get_call_destination(u8 type)
{
    struct paravirt_patch_template tmpl = {
        .pv_init_ops = pv_init_ops,
        .pv_time_ops = pv_time_ops,
        .pv_cpu_ops = pv_cpu_ops,
        .pv_irq_ops = pv_irq_ops,
        .pv_apic_ops = pv_apic_ops,
        .pv_mmu_ops = pv_mmu_ops,
#ifdef CONFIG_PARAVIRT_SPINLOCKS
        .pv_lock_ops = pv_lock_ops,
#endif
    };
    return *((void **)&tmpl + type);
}

unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
                unsigned long addr, unsigned len)
{
    void *opfunc = get_call_destination(type);
    unsigned ret;

    if (opfunc == NULL)
        /* If there's no function, patch it with a ud2a (BUG) */
        ret = paravirt_patch_insns(insnbuf, len, ud2a, ud2a+sizeof(ud2a));
    else if (opfunc == _paravirt_nop)
        /* If the operation is a nop, then nop the callsite */
        ret = paravirt_patch_nop();

    /* identity functions just return their single argument */
    else if (opfunc == _paravirt_ident_32)
        ret = paravirt_patch_ident_32(insnbuf, len);
    else if (opfunc == _paravirt_ident_64)
        ret = paravirt_patch_ident_64(insnbuf, len);

    else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) ||
         type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) ||
         type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) ||
         type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64))
        /* If operation requires a jmp, then jmp */
        ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len);
    else
        /* Otherwise call the function; assume target could
           clobber any caller-save reg */
        ret = paravirt_patch_call(insnbuf, opfunc, CLBR_ANY,
                      addr, clobbers, len);

    return ret;
}

unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
                  const char *start, const char *end)
{
    unsigned insn_len = end - start;

    if (insn_len > len || start == NULL)
        insn_len = len;
    else
        memcpy(insnbuf, start, insn_len);

    return insn_len;
}

static void native_flush_tlb(void)
{
    __native_flush_tlb();
}

/*
 * Global pages have to be flushed a bit differently. Not a real
 * performance problem because this does not happen often.
 */
static void native_flush_tlb_global(void)
{
    __native_flush_tlb_global();
}

static void native_flush_tlb_single(unsigned long addr)
{
    __native_flush_tlb_single(addr);
}

struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;

static u64 native_steal_clock(int cpu)
{
    return 0;
}

/* These are in entry.S */
extern void native_iret(void);
extern void native_irq_enable_sysexit(void);
extern void native_usergs_sysret32(void);
extern void native_usergs_sysret64(void);

static struct resource reserve_ioports = {
    .start = 0,
    .end = IO_SPACE_LIMIT,
    .name = "paravirt-ioport",
    .flags = IORESOURCE_IO | IORESOURCE_BUSY,
};

/*
 * Reserve the whole legacy IO space to prevent any legacy drivers
 * from wasting time probing for their hardware.  This is a fairly
 * brute-force approach to disabling all non-virtual drivers.
 *
 * Note that this must be called very early to have any effect.
 */
int paravirt_disable_iospace(void)
{
    return request_resource(&ioport_resource, &reserve_ioports);
}

static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;

static inline void enter_lazy(enum paravirt_lazy_mode mode)
{
    BUG_ON(this_cpu_read(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);

    this_cpu_write(paravirt_lazy_mode, mode);
}

static void leave_lazy(enum paravirt_lazy_mode mode)
{
    BUG_ON(this_cpu_read(paravirt_lazy_mode) != mode);

    this_cpu_write(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
}

void paravirt_enter_lazy_mmu(void)
{
    enter_lazy(PARAVIRT_LAZY_MMU);
}

void paravirt_leave_lazy_mmu(void)
{
    leave_lazy(PARAVIRT_LAZY_MMU);
}

void paravirt_start_context_switch(struct task_struct *prev)
{
    BUG_ON(preemptible());

    if (this_cpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
        arch_leave_lazy_mmu_mode();
        set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
    }
    enter_lazy(PARAVIRT_LAZY_CPU);
}

void paravirt_end_context_switch(struct task_struct *next)
{
    BUG_ON(preemptible());

    leave_lazy(PARAVIRT_LAZY_CPU);

    if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
        arch_enter_lazy_mmu_mode();
}

enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
{
    if (in_interrupt())
        return PARAVIRT_LAZY_NONE;

    return this_cpu_read(paravirt_lazy_mode);
}

void arch_flush_lazy_mmu_mode(void)
{
    preempt_disable();

    if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
        arch_leave_lazy_mmu_mode();
        arch_enter_lazy_mmu_mode();
    }

    preempt_enable();
}

struct pv_info pv_info = {
    .name = "bare hardware",
    .paravirt_enabled = 0,
    .kernel_rpl = 0,
    .shared_kernel_pmd = 1, /* Only used when CONFIG_X86_PAE is set */

#ifdef CONFIG_X86_64
    .extra_user_64bit_cs = __USER_CS,
#endif
};

struct pv_init_ops pv_init_ops = {
    .patch = native_patch,
};

struct pv_time_ops pv_time_ops = {
    .sched_clock = native_sched_clock,
    .steal_clock = native_steal_clock,
};

struct pv_irq_ops pv_irq_ops = {
    .save_fl = __PV_IS_CALLEE_SAVE(native_save_fl),
    .restore_fl = __PV_IS_CALLEE_SAVE(native_restore_fl),
    .irq_disable = __PV_IS_CALLEE_SAVE(native_irq_disable),
    .irq_enable = __PV_IS_CALLEE_SAVE(native_irq_enable),
    .safe_halt = native_safe_halt,
    .halt = native_halt,
#ifdef CONFIG_X86_64
    .adjust_exception_frame = paravirt_nop,
#endif
};

struct pv_cpu_ops pv_cpu_ops = {
    .cpuid = native_cpuid,
    .get_debugreg = native_get_debugreg,
    .set_debugreg = native_set_debugreg,
    .clts = native_clts,
    .read_cr0 = native_read_cr0,
    .write_cr0 = native_write_cr0,
    .read_cr4 = native_read_cr4,
    .read_cr4_safe = native_read_cr4_safe,
    .write_cr4 = native_write_cr4,
#ifdef CONFIG_X86_64
    .read_cr8 = native_read_cr8,
    .write_cr8 = native_write_cr8,
#endif
    .wbinvd = native_wbinvd,
    .read_msr = native_read_msr_safe,
    .write_msr = native_write_msr_safe,
    .read_tsc = native_read_tsc,
    .read_pmc = native_read_pmc,
    .read_tscp = native_read_tscp,
    .load_tr_desc = native_load_tr_desc,
    .set_ldt = native_set_ldt,
    .load_gdt = native_load_gdt,
    .load_idt = native_load_idt,
    .store_gdt = native_store_gdt,
    .store_idt = native_store_idt,
    .store_tr = native_store_tr,
    .load_tls = native_load_tls,
#ifdef CONFIG_X86_64
    .load_gs_index = native_load_gs_index,
#endif
    .write_ldt_entry = native_write_ldt_entry,
    .write_gdt_entry = native_write_gdt_entry,
    .write_idt_entry = native_write_idt_entry,

    .alloc_ldt = paravirt_nop,
    .free_ldt = paravirt_nop,

    .load_sp0 = native_load_sp0,

#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
    .irq_enable_sysexit = native_irq_enable_sysexit,
#endif
#ifdef CONFIG_X86_64
#ifdef CONFIG_IA32_EMULATION
    .usergs_sysret32 = native_usergs_sysret32,
#endif
    .usergs_sysret64 = native_usergs_sysret64,
#endif
    .iret = native_iret,
    .swapgs = native_swapgs,

    .set_iopl_mask = native_set_iopl_mask,
    .io_delay = native_io_delay,

    .start_context_switch = paravirt_nop,
    .end_context_switch = paravirt_nop,
};

struct pv_apic_ops pv_apic_ops = {
#ifdef CONFIG_X86_LOCAL_APIC
    .startup_ipi_hook = paravirt_nop,
#endif
};

#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
/* 32-bit pagetable entries */
#define PTE_IDENT   __PV_IS_CALLEE_SAVE(_paravirt_ident_32)
#else
/* 64-bit pagetable entries */
#define PTE_IDENT   __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
#endif

struct pv_mmu_ops pv_mmu_ops = {

    .read_cr2 = native_read_cr2,
    .write_cr2 = native_write_cr2,
    .read_cr3 = native_read_cr3,
    .write_cr3 = native_write_cr3,

    .flush_tlb_user = native_flush_tlb,
    .flush_tlb_kernel = native_flush_tlb_global,
    .flush_tlb_single = native_flush_tlb_single,
    .flush_tlb_others = native_flush_tlb_others,

    .pgd_alloc = __paravirt_pgd_alloc,
    .pgd_free = paravirt_nop,

    .alloc_pte = paravirt_nop,
    .alloc_pmd = paravirt_nop,
    .alloc_pud = paravirt_nop,
    .release_pte = paravirt_nop,
    .release_pmd = paravirt_nop,
    .release_pud = paravirt_nop,

    .set_pte = native_set_pte,
    .set_pte_at = native_set_pte_at,
    .set_pmd = native_set_pmd,
    .set_pmd_at = native_set_pmd_at,
    .pte_update = paravirt_nop,
    .pte_update_defer = paravirt_nop,
    .pmd_update = paravirt_nop,
    .pmd_update_defer = paravirt_nop,

    .ptep_modify_prot_start = __ptep_modify_prot_start,
    .ptep_modify_prot_commit = __ptep_modify_prot_commit,

#if PAGETABLE_LEVELS >= 3
#ifdef CONFIG_X86_PAE
    .set_pte_atomic = native_set_pte_atomic,
    .pte_clear = native_pte_clear,
    .pmd_clear = native_pmd_clear,
#endif
    .set_pud = native_set_pud,

    .pmd_val = PTE_IDENT,
    .make_pmd = PTE_IDENT,

#if PAGETABLE_LEVELS == 4
    .pud_val = PTE_IDENT,
    .make_pud = PTE_IDENT,

    .set_pgd = native_set_pgd,
#endif
#endif /* PAGETABLE_LEVELS >= 3 */

    .pte_val = PTE_IDENT,
    .pgd_val = PTE_IDENT,

    .make_pte = PTE_IDENT,
    .make_pgd = PTE_IDENT,

    .dup_mmap = paravirt_nop,
    .exit_mmap = paravirt_nop,
    .activate_mm = paravirt_nop,

    .lazy_mode = {
        .enter = paravirt_nop,
        .leave = paravirt_nop,
    },

    .set_fixmap = native_set_fixmap,
};

EXPORT_SYMBOL_GPL(pv_time_ops);
EXPORT_SYMBOL    (pv_cpu_ops);
EXPORT_SYMBOL    (pv_mmu_ops);
EXPORT_SYMBOL_GPL(pv_apic_ops);
EXPORT_SYMBOL_GPL(pv_info);
EXPORT_SYMBOL    (pv_irq_ops);