[PATCH 08/11] KVM: MMU: split kvm_mmu_pte_write function

Xiao Guangrong
2011-07-26T11:28:47Z

kvm_mmu_pte_write is too long, we split it for better readable

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/mmu.c | 180 ++++++++++++++++++++++++++++++++--------------------
1 files changed, 111 insertions(+), 69 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 7629802..931c23a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3524,48 +3524,29 @@ static int get_free_pte_list_desc_nr(struct kvm_vcpu *vcpu)
return mmu_memory_cache_free_object(cache);
}

-void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
- const u8 *new, int bytes, bool repeat_write)
+static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa,
+ const u8 *new, int *bytes)
{
- gfn_t gfn = gpa >> PAGE_SHIFT;
- union kvm_mmu_page_role mask = { .word = 0 };
- struct kvm_mmu_page *sp;
- struct hlist_node *node;
- LIST_HEAD(invalid_list);
- u64 entry, gentry, *spte;
- unsigned pte_size, page_offset, misaligned, quadrant, offset;
- int level, npte, r, flooded = 0;
- bool remote_flush, local_flush, zap_page;
-
- /*
- * If we don't have indirect shadow pages, it means no page is
- * write-protected, so we can exit simply.
- */
- if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
- return;
-
- zap_page = remote_flush = local_flush = false;
- offset = offset_in_page(gpa);
-
- pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
+ u64 gentry;
+ int r;

/*
* Assume that the pte write on a page table of the same type
* as the current vcpu paging mode since we update the sptes only
* when they have the same mode.
*/
- if (is_pae(vcpu) && bytes == 4) {
+ if (is_pae(vcpu) && *bytes == 4) {
/* Handle a 32-bit guest writing two halves of a 64-bit gpte */
- gpa &= ~(gpa_t)7;
- bytes = 8;
+ *gpa &= ~(gpa_t)7;
+ *bytes = 8;

- r = kvm_read_guest(vcpu->kvm, gpa, &gentry, min(bytes, 8));
+ r = kvm_read_guest(vcpu->kvm, *gpa, &gentry, min(*bytes, 8));
if (r)
gentry = 0;
new = (const u8 *)&gentry;
}

- switch (bytes) {
+ switch (*bytes) {
case 4:
gentry = *(const u32 *)new;
break;
@@ -3577,66 +3558,127 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
break;
}

- mmu_topup_memory_caches(vcpu);
- spin_lock(&vcpu->kvm->mmu_lock);
- ++vcpu->kvm->stat.mmu_pte_write;
- trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
+ return gentry;
+}
+
+/*
+ * If we're seeing too many writes to a page, it may no longer be a page table,
+ * or we may be forking, in which case it is better to unmap the page.
+ */
+static bool detect_write_flooding(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+ bool flooded = false;
+
if (gfn == vcpu->arch.last_pt_write_gfn
&& !last_updated_pte_accessed(vcpu)) {
++vcpu->arch.last_pt_write_count;
if (vcpu->arch.last_pt_write_count >= 3)
- flooded = 1;
+ flooded = true;
} else {
vcpu->arch.last_pt_write_gfn = gfn;
vcpu->arch.last_pt_write_count = 1;
vcpu->arch.last_pte_updated = NULL;
}

+ return flooded;
+}
+
+/*
+ * Misaligned accesses are too much trouble to fix up; also, they usually
+ * indicate a page is not used as a page table.
+ */
+static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa,
+ int bytes)
+{
+ unsigned offset, pte_size, misaligned;
+
+ pgprintk("misaligned: gpa %llx bytes %d role %x\n",
+ gpa, bytes, sp->role.word);
+
+ offset = offset_in_page(gpa);
+ pte_size = sp->role.cr4_pae ? 8 : 4;
+ misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
+ misaligned |= bytes < 4;
+
+ return misaligned;
+}
+
+static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
+{
+ unsigned page_offset, quadrant;
+ u64 *spte;
+ int level;
+
+ page_offset = offset_in_page(gpa);
+ level = sp->role.level;
+ *nspte = 1;
+ if (!sp->role.cr4_pae) {
+ page_offset <<= 1; /* 32->64 */
+ /*
+ * A 32-bit pde maps 4MB while the shadow pdes map
+ * only 2MB. So we need to double the offset again
+ * and zap two pdes instead of one.
+ */
+ if (level == PT32_ROOT_LEVEL) {
+ page_offset &= ~7; /* kill rounding error */
+ page_offset <<= 1;
+ *nspte = 2;
+ }
+ quadrant = page_offset >> PAGE_SHIFT;
+ page_offset &= ~PAGE_MASK;
+ if (quadrant != sp->role.quadrant)
+ return NULL;
+ }
+
+ spte = &sp->spt[page_offset / sizeof(*spte)];
+ return spte;
+}
+
+void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+ const u8 *new, int bytes, bool repeat_write)
+{
+ gfn_t gfn = gpa >> PAGE_SHIFT;
+ union kvm_mmu_page_role mask = { .word = 0 };
+ struct kvm_mmu_page *sp;
+ struct hlist_node *node;
+ LIST_HEAD(invalid_list);
+ u64 entry, gentry, *spte;
+ int npte;
+ bool remote_flush, local_flush, zap_page, flooded, misaligned;
+
+ /*
+ * If we don't have indirect shadow pages, it means no page is
+ * write-protected, so we can exit simply.
+ */
+ if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
+ return;
+
+ zap_page = remote_flush = local_flush = false;
+
+ pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
+
+ gentry = mmu_pte_write_fetch_gpte(vcpu, &gpa, new, &bytes);
+ mmu_topup_memory_caches(vcpu);
+ spin_lock(&vcpu->kvm->mmu_lock);
+ ++vcpu->kvm->stat.mmu_pte_write;
+ trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
+
+ flooded = detect_write_flooding(vcpu, gfn);
mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn, node) {
- pte_size = sp->role.cr4_pae ? 8 : 4;
- misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
- misaligned |= bytes < 4;
+ misaligned = detect_write_misaligned(sp, gpa, bytes);
if (misaligned || flooded || repeat_write) {
- /*
- * Misaligned accesses are too much trouble to fix
- * up; also, they usually indicate a page is not used
- * as a page table.
- *
- * If we're seeing too many writes to a page,
- * it may no longer be a page table, or we may be
- * forking, in which case it is better to unmap the
- * page.
- */
- pgprintk("misaligned: gpa %llx bytes %d role %x\n",
- gpa, bytes, sp->role.word);
zap_page |= !!kvm_mmu_prepare_zap_page(vcpu->kvm, sp,
&invalid_list);
++vcpu->kvm->stat.mmu_flooded;
continue;
}
- page_offset = offset;
- level = sp->role.level;
- npte = 1;
- if (!sp->role.cr4_pae) {
- page_offset <<= 1; /* 32->64 */
- /*
- * A 32-bit pde maps 4MB while the shadow pdes map
- * only 2MB. So we need to double the offset again
- * and zap two pdes instead of one.
- */
- if (level == PT32_ROOT_LEVEL) {
- page_offset &= ~7; /* kill rounding error */
- page_offset <<= 1;
- npte = 2;
- }
- quadrant = page_offset >> PAGE_SHIFT;
- page_offset &= ~PAGE_MASK;
- if (quadrant != sp->role.quadrant)
- continue;
- }
+
+ spte = get_written_sptes(sp, gpa, &npte);
+ if (!spte)
+ continue;
+
local_flush = true;
- spte = &sp->spt[page_offset / sizeof(*spte)];
while (npte--) {
entry = *spte;
mmu_page_zap_pte(vcpu->kvm, sp, spte);
--
1.7.5.4