KVM: MMU: Optimize is_last_gpte()
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>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9c61889..d289fee 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3447,6 +3447,15 @@
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_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 @@
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 @@
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 @@
}
update_permission_bitmask(vcpu, context);
+ update_last_pte_bitmap(vcpu, context);
return 0;
}
@@ -3724,6 +3754,7 @@
}
update_permission_bitmask(vcpu, g_context);
+ update_last_pte_bitmap(vcpu, g_context);
return 0;
}