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KVM: MMU: Optimize is_last_gpte()

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Instead of branchy code depending on level, gpte.ps, and mmu configuration,
prepare everything in a bitmap during mode changes and look it up during
runtime.

Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity 2012-09-12 20:46:56 +03:00
parent 13d22b6aeb
commit 6fd01b711b
4 changed files with 41 additions and 20 deletions
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7
arch/x86/include/asm/kvm_host.h
View File

@ -298,6 +298,13 @@ struct kvm_mmu {
u64 *lm_root;
u64 rsvd_bits_mask[2][4];
/*
* Bitmap: bit set = last pte in walk
* index[0:1]: level (zero-based)
* index[2]: pte.ps
*/
u8 last_pte_bitmap;
bool nx;
u64 pdptrs[4]; /* pae */

31
arch/x86/kvm/mmu.c
View File

@ -3447,6 +3447,15 @@ static inline unsigned gpte_access(struct kvm_vcpu *vcpu, u64 gpte)
return access;
}
static inline bool is_last_gpte(struct kvm_mmu *mmu, unsigned level, unsigned gpte)
{
unsigned index;
index = level - 1;
index |= (gpte & PT_PAGE_SIZE_MASK) >> (PT_PAGE_SIZE_SHIFT - 2);
return mmu->last_pte_bitmap & (1 << index);
}
#define PTTYPE 64
#include "paging_tmpl.h"
#undef PTTYPE
@ -3548,6 +3557,24 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu
}
}
static void update_last_pte_bitmap(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
u8 map;
unsigned level, root_level = mmu->root_level;
const unsigned ps_set_index = 1 << 2; /* bit 2 of index: ps */
if (root_level == PT32E_ROOT_LEVEL)
--root_level;
/* PT_PAGE_TABLE_LEVEL always terminates */
map = 1 | (1 << ps_set_index);
for (level = PT_DIRECTORY_LEVEL; level <= root_level; ++level) {
if (level <= PT_PDPE_LEVEL
&& (mmu->root_level >= PT32E_ROOT_LEVEL || is_pse(vcpu)))
map |= 1 << (ps_set_index | (level - 1));
}
mmu->last_pte_bitmap = map;
}
static int paging64_init_context_common(struct kvm_vcpu *vcpu,
struct kvm_mmu *context,
int level)
@ -3557,6 +3584,7 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu,
reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context);
update_last_pte_bitmap(vcpu, context);
ASSERT(is_pae(vcpu));
context->new_cr3 = paging_new_cr3;
@ -3586,6 +3614,7 @@ static int paging32_init_context(struct kvm_vcpu *vcpu,
reset_rsvds_bits_mask(vcpu, context);
update_permission_bitmask(vcpu, context);
update_last_pte_bitmap(vcpu, context);
context->new_cr3 = paging_new_cr3;
context->page_fault = paging32_page_fault;
@ -3647,6 +3676,7 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
}
update_permission_bitmask(vcpu, context);
update_last_pte_bitmap(vcpu, context);
return 0;
}
@ -3724,6 +3754,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
}
update_permission_bitmask(vcpu, g_context);
update_last_pte_bitmap(vcpu, g_context);
return 0;
}

3
arch/x86/kvm/mmu.h
View File

@ -20,7 +20,8 @@
#define PT_ACCESSED_MASK (1ULL << PT_ACCESSED_SHIFT)
#define PT_DIRTY_SHIFT 6
#define PT_DIRTY_MASK (1ULL << PT_DIRTY_SHIFT)
#define PT_PAGE_SIZE_MASK (1ULL << 7)
#define PT_PAGE_SIZE_SHIFT 7
#define PT_PAGE_SIZE_MASK (1ULL << PT_PAGE_SIZE_SHIFT)
#define PT_PAT_MASK (1ULL << 7)
#define PT_GLOBAL_MASK (1ULL << 8)
#define PT64_NX_SHIFT 63

20
arch/x86/kvm/paging_tmpl.h
View File

@ -103,24 +103,6 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
return (ret != orig_pte);
}
static bool FNAME(is_last_gpte)(struct guest_walker *walker,
struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
pt_element_t gpte)
{
if (walker->level == PT_PAGE_TABLE_LEVEL)
return true;
if ((walker->level == PT_DIRECTORY_LEVEL) && is_large_pte(gpte) &&
(PTTYPE == 64 || is_pse(vcpu)))
return true;
if ((walker->level == PT_PDPE_LEVEL) && is_large_pte(gpte) &&
(mmu->root_level == PT64_ROOT_LEVEL))
return true;
return false;
}
static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
struct kvm_mmu *mmu,
struct guest_walker *walker,
@ -247,7 +229,7 @@ retry_walk:
pte_access = pt_access & gpte_access(vcpu, pte);
walker->ptes[walker->level - 1] = pte;
} while (!FNAME(is_last_gpte)(walker, vcpu, mmu, pte));
} while (!is_last_gpte(mmu, walker->level, pte));
eperm |= permission_fault(mmu, pte_access, access);
if (unlikely(eperm)) {