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Message-Id: <1198421495-31481-44-git-send-email-avi@qumranet.com>
Date: Sun, 23 Dec 2007 16:51:28 +0200
From: Avi Kivity <avi@...ranet.com>
To: linux-kernel@...r.kernel.org, kvm-devel@...ts.sourceforge.net
Subject: [PATCH 43/50] KVM: MMU: Simplify page table walker
Simplify the walker level loop not to carry so much information from one
loop to the next. In addition to being complex, this made kmap_atomic()
critical sections difficult to manage.
As a result of this change, kmap_atomic() sections are limited to actually
touching the guest pte, which allows the other functions called from the
walker to do sleepy operations. This will happen when we enable swapping.
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
drivers/kvm/paging_tmpl.h | 124 +++++++++++++++++---------------------------
1 files changed, 48 insertions(+), 76 deletions(-)
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index a9e687b..bab1b7f 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -59,32 +59,12 @@
struct guest_walker {
int level;
gfn_t table_gfn[PT_MAX_FULL_LEVELS];
- pt_element_t *table;
pt_element_t pte;
- pt_element_t *ptep;
- struct page *page;
- int index;
pt_element_t inherited_ar;
gfn_t gfn;
u32 error_code;
};
-static void FNAME(update_dirty_bit)(struct kvm_vcpu *vcpu,
- int write_fault,
- pt_element_t *ptep,
- gfn_t table_gfn)
-{
- gpa_t pte_gpa;
-
- if (write_fault && !is_dirty_pte(*ptep)) {
- mark_page_dirty(vcpu->kvm, table_gfn);
- *ptep |= PT_DIRTY_MASK;
- pte_gpa = ((gpa_t)table_gfn << PAGE_SHIFT);
- pte_gpa += offset_in_page(ptep);
- kvm_mmu_pte_write(vcpu, pte_gpa, (u8 *)ptep, sizeof(*ptep));
- }
-}
-
/*
* Fetch a guest pte for a guest virtual address
*/
@@ -94,105 +74,99 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
{
hpa_t hpa;
struct kvm_memory_slot *slot;
- pt_element_t *ptep;
- pt_element_t root;
+ struct page *page;
+ pt_element_t *table;
+ pt_element_t pte;
gfn_t table_gfn;
+ unsigned index;
+ gpa_t pte_gpa;
pgprintk("%s: addr %lx\n", __FUNCTION__, addr);
walker->level = vcpu->mmu.root_level;
- walker->table = NULL;
- walker->page = NULL;
- walker->ptep = NULL;
- root = vcpu->cr3;
+ pte = vcpu->cr3;
#if PTTYPE == 64
if (!is_long_mode(vcpu)) {
- walker->ptep = &vcpu->pdptrs[(addr >> 30) & 3];
- root = *walker->ptep;
- walker->pte = root;
- if (!(root & PT_PRESENT_MASK))
+ pte = vcpu->pdptrs[(addr >> 30) & 3];
+ if (!is_present_pte(pte))
goto not_present;
--walker->level;
}
#endif
- table_gfn = (root & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
- walker->table_gfn[walker->level - 1] = table_gfn;
- pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
- walker->level - 1, table_gfn);
- slot = gfn_to_memslot(vcpu->kvm, table_gfn);
- hpa = safe_gpa_to_hpa(vcpu->kvm, root & PT64_BASE_ADDR_MASK);
- walker->page = pfn_to_page(hpa >> PAGE_SHIFT);
- walker->table = kmap_atomic(walker->page, KM_USER0);
-
ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
(vcpu->cr3 & CR3_NONPAE_RESERVED_BITS) == 0);
walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;
for (;;) {
- int index = PT_INDEX(addr, walker->level);
- hpa_t paddr;
+ index = PT_INDEX(addr, walker->level);
- ptep = &walker->table[index];
- walker->index = index;
- ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
- ((unsigned long)ptep & PAGE_MASK));
+ table_gfn = (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
+ walker->table_gfn[walker->level - 1] = table_gfn;
+ pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
+ walker->level - 1, table_gfn);
+
+ slot = gfn_to_memslot(vcpu->kvm, table_gfn);
+ hpa = safe_gpa_to_hpa(vcpu->kvm, pte & PT64_BASE_ADDR_MASK);
+ page = pfn_to_page(hpa >> PAGE_SHIFT);
- if (!is_present_pte(*ptep))
+ table = kmap_atomic(page, KM_USER0);
+ pte = table[index];
+ kunmap_atomic(table, KM_USER0);
+
+ if (!is_present_pte(pte))
goto not_present;
- if (write_fault && !is_writeble_pte(*ptep))
+ if (write_fault && !is_writeble_pte(pte))
if (user_fault || is_write_protection(vcpu))
goto access_error;
- if (user_fault && !(*ptep & PT_USER_MASK))
+ if (user_fault && !(pte & PT_USER_MASK))
goto access_error;
#if PTTYPE == 64
- if (fetch_fault && is_nx(vcpu) && (*ptep & PT64_NX_MASK))
+ if (fetch_fault && is_nx(vcpu) && (pte & PT64_NX_MASK))
goto access_error;
#endif
- if (!(*ptep & PT_ACCESSED_MASK)) {
+ if (!(pte & PT_ACCESSED_MASK)) {
mark_page_dirty(vcpu->kvm, table_gfn);
- *ptep |= PT_ACCESSED_MASK;
+ pte |= PT_ACCESSED_MASK;
+ table = kmap_atomic(page, KM_USER0);
+ table[index] = pte;
+ kunmap_atomic(table, KM_USER0);
}
if (walker->level == PT_PAGE_TABLE_LEVEL) {
- walker->gfn = (*ptep & PT_BASE_ADDR_MASK)
- >> PAGE_SHIFT;
- FNAME(update_dirty_bit)(vcpu, write_fault, ptep,
- table_gfn);
+ walker->gfn = (pte & PT_BASE_ADDR_MASK) >> PAGE_SHIFT;
break;
}
if (walker->level == PT_DIRECTORY_LEVEL
- && (*ptep & PT_PAGE_SIZE_MASK)
+ && (pte & PT_PAGE_SIZE_MASK)
&& (PTTYPE == 64 || is_pse(vcpu))) {
- walker->gfn = (*ptep & PT_DIR_BASE_ADDR_MASK)
+ walker->gfn = (pte & PT_DIR_BASE_ADDR_MASK)
>> PAGE_SHIFT;
walker->gfn += PT_INDEX(addr, PT_PAGE_TABLE_LEVEL);
- FNAME(update_dirty_bit)(vcpu, write_fault, ptep,
- table_gfn);
break;
}
- walker->inherited_ar &= walker->table[index];
- table_gfn = (*ptep & PT_BASE_ADDR_MASK) >> PAGE_SHIFT;
- kunmap_atomic(walker->table, KM_USER0);
- paddr = safe_gpa_to_hpa(vcpu->kvm, table_gfn << PAGE_SHIFT);
- walker->page = pfn_to_page(paddr >> PAGE_SHIFT);
- walker->table = kmap_atomic(walker->page, KM_USER0);
+ walker->inherited_ar &= pte;
--walker->level;
- walker->table_gfn[walker->level - 1] = table_gfn;
- pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
- walker->level - 1, table_gfn);
}
- walker->pte = *ptep;
- if (walker->page)
- walker->ptep = NULL;
- if (walker->table)
- kunmap_atomic(walker->table, KM_USER0);
- pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)*ptep);
+
+ if (write_fault && !is_dirty_pte(pte)) {
+ mark_page_dirty(vcpu->kvm, table_gfn);
+ pte |= PT_DIRTY_MASK;
+ table = kmap_atomic(page, KM_USER0);
+ table[index] = pte;
+ kunmap_atomic(table, KM_USER0);
+ pte_gpa = table_gfn << PAGE_SHIFT;
+ pte_gpa += index * sizeof(pt_element_t);
+ kvm_mmu_pte_write(vcpu, pte_gpa, (u8 *)&pte, sizeof(pte));
+ }
+
+ walker->pte = pte;
+ pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)pte);
return 1;
not_present:
@@ -209,8 +183,6 @@ err:
walker->error_code |= PFERR_USER_MASK;
if (fetch_fault)
walker->error_code |= PFERR_FETCH_MASK;
- if (walker->table)
- kunmap_atomic(walker->table, KM_USER0);
return 0;
}
--
1.5.3.7
--
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