x86/pvops: add a paravirt_ident functions to allow special patching

Impact: Optimization

Several paravirt ops implementations simply return their arguments,
the most obvious being the make_pte/pte_val class of operations on
native.

On 32-bit, the identity function is literally a no-op, as the calling
convention uses the same registers for the first argument and return.
On 64-bit, it can be implemented with a single "mov".

This patch adds special identity functions for 32 and 64 bit argument,
and machinery to recognize them and replace them with either nops or a
mov as appropriate.

At the moment, the only users for the identity functions are the
pagetable entry conversion functions.

The result is a measureable improvement on pagetable-heavy benchmarks
(2-3%, reducing the pvops overhead from 5 to 2%).

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Jeremy Fitzhardinge 2009-01-28 14:35:02 -08:00 committed by H. Peter Anvin
parent 319f3ba52c
commit 41edafdb78
4 changed files with 98 additions and 9 deletions

View File

@ -388,6 +388,8 @@ extern struct pv_lock_ops pv_lock_ops;
asm("start_" #ops "_" #name ": " code "; end_" #ops "_" #name ":")
unsigned paravirt_patch_nop(void);
unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len);
unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len);
unsigned paravirt_patch_ignore(unsigned len);
unsigned paravirt_patch_call(void *insnbuf,
const void *target, u16 tgt_clobbers,
@ -1371,6 +1373,9 @@ static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
}
void _paravirt_nop(void);
u32 _paravirt_ident_32(u32);
u64 _paravirt_ident_64(u64);
#define paravirt_nop ((void *)_paravirt_nop)
void paravirt_use_bytelocks(void);

View File

@ -44,6 +44,17 @@ 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",
@ -138,9 +149,16 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
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)
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) ||
@ -373,6 +391,45 @@ struct pv_apic_ops pv_apic_ops = {
#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,
@ -424,21 +481,21 @@ struct pv_mmu_ops pv_mmu_ops = {
.pmd_clear = native_pmd_clear,
#endif
.set_pud = native_set_pud,
.pmd_val = native_pmd_val,
.make_pmd = native_make_pmd,
.pmd_val = paravirt_native_pmd_val,
.make_pmd = paravirt_native_make_pmd,
#if PAGETABLE_LEVELS == 4
.pud_val = native_pud_val,
.make_pud = native_make_pud,
.pud_val = paravirt_native_pud_val,
.make_pud = paravirt_native_make_pud,
.set_pgd = native_set_pgd,
#endif
#endif /* PAGETABLE_LEVELS >= 3 */
.pte_val = native_pte_val,
.pgd_val = native_pgd_val,
.pte_val = paravirt_native_pte_val,
.pgd_val = paravirt_native_pgd_val,
.make_pte = native_make_pte,
.make_pgd = native_make_pgd,
.make_pte = paravirt_native_make_pte,
.make_pgd = paravirt_native_make_pgd,
.dup_mmap = paravirt_nop,
.exit_mmap = paravirt_nop,

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@ -12,6 +12,18 @@ DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
DEF_NATIVE(pv_cpu_ops, clts, "clts");
DEF_NATIVE(pv_cpu_ops, read_tsc, "rdtsc");
unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len)
{
/* arg in %eax, return in %eax */
return 0;
}
unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len)
{
/* arg in %edx:%eax, return in %edx:%eax */
return 0;
}
unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
unsigned long addr, unsigned len)
{

View File

@ -19,6 +19,21 @@ DEF_NATIVE(pv_cpu_ops, usergs_sysret64, "swapgs; sysretq");
DEF_NATIVE(pv_cpu_ops, usergs_sysret32, "swapgs; sysretl");
DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs");
DEF_NATIVE(, mov32, "mov %edi, %eax");
DEF_NATIVE(, mov64, "mov %rdi, %rax");
unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len)
{
return paravirt_patch_insns(insnbuf, len,
start__mov32, end__mov32);
}
unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len)
{
return paravirt_patch_insns(insnbuf, len,
start__mov64, end__mov64);
}
unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
unsigned long addr, unsigned len)
{