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linux/arch/x86/kernel/paravirt.c
Jeremy Fitzhardinge ecb93d1ccd x86/paravirt: add register-saving thunks to reduce caller register pressure 
Impact: Optimization

One of the problems with inserting a pile of C calls where previously
there were none is that the register pressure is greatly increased.
The C calling convention says that the caller must expect a certain
set of registers may be trashed by the callee, and that the callee can
use those registers without restriction.  This includes the function
argument registers, and several others.

This patch seeks to alleviate this pressure by introducing wrapper
thunks that will do the register saving/restoring, so that the
callsite doesn't need to worry about it, but the callee function can
be conventional compiler-generated code.  In many cases (particularly
performance-sensitive cases) the callee will be in assembler anyway,
and need not use the compiler's calling convention.

Standard calling convention is:
	 arguments	    return	scratch
x86-32	 eax edx ecx	    eax		?
x86-64	 rdi rsi rdx rcx    rax		r8 r9 r10 r11

The thunk preserves all argument and scratch registers.  The return
register is not preserved, and is available as a scratch register for
unwrapped callee code (and of course the return value).

Wrapped function pointers are themselves wrapped in a struct
paravirt_callee_save structure, in order to get some warning from the
compiler when functions with mismatched calling conventions are used.

The most common paravirt ops, both statically and dynamically, are
interrupt enable/disable/save/restore, so handle them first.  This is
particularly easy since their calls are handled specially anyway.

XXX Deal with VMI.  What's their calling convention?

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2009-01-30 14:51:45 -08:00

518 lines
13 KiB
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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/desc.h>
#include <asm/setup.h>
#include <asm/arch_hooks.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>
/* 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;
}
static void __init default_banner(void)
{
printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
pv_info.name);
}
char *memory_setup(void)
{
return pv_init_ops.memory_setup();
}
/* 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,
.pv_lock_ops = pv_lock_ops,
};
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;
}
void init_IRQ(void)
{
pv_irq_ops.init_IRQ();
}
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);
}
/* 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 int __init print_banner(void)
{
pv_init_ops.banner();
return 0;
}
core_initcall(print_banner);
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(__get_cpu_var(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
BUG_ON(preemptible());
__get_cpu_var(paravirt_lazy_mode) = mode;
}
void paravirt_leave_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(__get_cpu_var(paravirt_lazy_mode) != mode);
BUG_ON(preemptible());
__get_cpu_var(paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
}
void paravirt_enter_lazy_mmu(void)
{
enter_lazy(PARAVIRT_LAZY_MMU);
}
void paravirt_leave_lazy_mmu(void)
{
paravirt_leave_lazy(PARAVIRT_LAZY_MMU);
}
void paravirt_enter_lazy_cpu(void)
{
enter_lazy(PARAVIRT_LAZY_CPU);
}
void paravirt_leave_lazy_cpu(void)
{
paravirt_leave_lazy(PARAVIRT_LAZY_CPU);
}
enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
{
return __get_cpu_var(paravirt_lazy_mode);
}
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 */
};
struct pv_init_ops pv_init_ops = {
.patch = native_patch,
.banner = default_banner,
.arch_setup = paravirt_nop,
.memory_setup = machine_specific_memory_setup,
};
struct pv_time_ops pv_time_ops = {
.time_init = hpet_time_init,
.get_wallclock = native_get_wallclock,
.set_wallclock = native_set_wallclock,
.sched_clock = native_sched_clock,
.get_tsc_khz = native_calibrate_tsc,
};
struct pv_irq_ops pv_irq_ops = {
.init_IRQ = native_init_IRQ,
.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,
.read_msr_amd = native_read_msr_amd_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,
.lazy_mode = {
.enter = paravirt_nop,
.leave = paravirt_nop,
},
};
struct pv_apic_ops pv_apic_ops = {
#ifdef CONFIG_X86_LOCAL_APIC
.setup_boot_clock = setup_boot_APIC_clock,
.setup_secondary_clock = setup_secondary_APIC_clock,
.startup_ipi_hook = paravirt_nop,
#endif
};
typedef pte_t make_pte_t(pteval_t);
typedef pmd_t make_pmd_t(pmdval_t);
typedef pud_t make_pud_t(pudval_t);
typedef pgd_t make_pgd_t(pgdval_t);
typedef pteval_t pte_val_t(pte_t);
typedef pmdval_t pmd_val_t(pmd_t);
typedef pudval_t pud_val_t(pud_t);
typedef pgdval_t pgd_val_t(pgd_t);
#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
/* 32-bit pagetable entries */
#define paravirt_native_make_pte (make_pte_t *)_paravirt_ident_32
#define paravirt_native_pte_val (pte_val_t *)_paravirt_ident_32
#define paravirt_native_make_pmd (make_pmd_t *)_paravirt_ident_32
#define paravirt_native_pmd_val (pmd_val_t *)_paravirt_ident_32
#define paravirt_native_make_pud (make_pud_t *)_paravirt_ident_32
#define paravirt_native_pud_val (pud_val_t *)_paravirt_ident_32
#define paravirt_native_make_pgd (make_pgd_t *)_paravirt_ident_32
#define paravirt_native_pgd_val (pgd_val_t *)_paravirt_ident_32
#else
/* 64-bit pagetable entries */
#define paravirt_native_make_pte (make_pte_t *)_paravirt_ident_64
#define paravirt_native_pte_val (pte_val_t *)_paravirt_ident_64
#define paravirt_native_make_pmd (make_pmd_t *)_paravirt_ident_64
#define paravirt_native_pmd_val (pmd_val_t *)_paravirt_ident_64
#define paravirt_native_make_pud (make_pud_t *)_paravirt_ident_64
#define paravirt_native_pud_val (pud_val_t *)_paravirt_ident_64
#define paravirt_native_make_pgd (make_pgd_t *)_paravirt_ident_64
#define paravirt_native_pgd_val (pgd_val_t *)_paravirt_ident_64
#endif
struct pv_mmu_ops pv_mmu_ops = {
#ifndef CONFIG_X86_64
.pagetable_setup_start = native_pagetable_setup_start,
.pagetable_setup_done = native_pagetable_setup_done,
#else
.pagetable_setup_start = paravirt_nop,
.pagetable_setup_done = paravirt_nop,
#endif
.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_pmd_clone = 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,
.pte_update = paravirt_nop,
.pte_update_defer = paravirt_nop,
.ptep_modify_prot_start = __ptep_modify_prot_start,
.ptep_modify_prot_commit = __ptep_modify_prot_commit,
#ifdef CONFIG_HIGHPTE
.kmap_atomic_pte = kmap_atomic,
#endif
#if PAGETABLE_LEVELS >= 3
#ifdef CONFIG_X86_PAE
.set_pte_atomic = native_set_pte_atomic,
.set_pte_present = native_set_pte_present,
.pte_clear = native_pte_clear,
.pmd_clear = native_pmd_clear,
#endif
.set_pud = native_set_pud,
.pmd_val = paravirt_native_pmd_val,
.make_pmd = paravirt_native_make_pmd,
#if PAGETABLE_LEVELS == 4
.pud_val = paravirt_native_pud_val,
.make_pud = paravirt_native_make_pud,
.set_pgd = native_set_pgd,
#endif
#endif /* PAGETABLE_LEVELS >= 3 */
.pte_val = paravirt_native_pte_val,
.pgd_val = paravirt_native_pgd_val,
.make_pte = paravirt_native_make_pte,
.make_pgd = paravirt_native_make_pgd,
.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);
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