Since gfn_to_page() is a sleeping function, and we want to make the core mmu
spinlocked, we need to pass the page from the walker context (which can sleep)
to the shadow context (which cannot).
Signed-off-by: Avi Kivity <[EMAIL PROTECTED]>
---
arch/x86/kvm/mmu.c | 58 ++++++++++++++++++++++++++++++++++++++++----
arch/x86/kvm/paging_tmpl.h | 25 +++++++++++++++----
include/asm-x86/kvm_host.h | 5 ++++
3 files changed, 78 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3b91227..1b68f07 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -890,11 +890,10 @@ struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva)
static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte,
unsigned pt_access, unsigned pte_access,
int user_fault, int write_fault, int dirty,
- int *ptwrite, gfn_t gfn)
+ int *ptwrite, gfn_t gfn, struct page *page)
{
u64 spte;
int was_rmapped = is_rmap_pte(*shadow_pte);
- struct page *page;
pgprintk("%s: spte %llx access %x write_fault %d"
" user_fault %d gfn %lx\n",
@@ -912,8 +911,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64
*shadow_pte,
if (!(pte_access & ACC_EXEC_MASK))
spte |= PT64_NX_MASK;
- page = gfn_to_page(vcpu->kvm, gfn);
-
spte |= PT_PRESENT_MASK;
if (pte_access & ACC_USER_MASK)
spte |= PT_USER_MASK;
@@ -979,6 +976,11 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t v,
int write, gfn_t gfn)
int level = PT32E_ROOT_LEVEL;
hpa_t table_addr = vcpu->arch.mmu.root_hpa;
int pt_write = 0;
+ struct page *page;
+
+ down_read(¤t->mm->mmap_sem);
+ page = gfn_to_page(vcpu->kvm, gfn);
+ up_read(¤t->mm->mmap_sem);
for (; ; level--) {
u32 index = PT64_INDEX(v, level);
@@ -989,7 +991,7 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t v,
int write, gfn_t gfn)
if (level == 1) {
mmu_set_spte(vcpu, &table[index], ACC_ALL, ACC_ALL,
- 0, write, 1, &pt_write, gfn);
+ 0, write, 1, &pt_write, gfn, page);
return pt_write || is_io_pte(table[index]);
}
@@ -1005,6 +1007,7 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t
v, int write, gfn_t gfn)
NULL);
if (!new_table) {
pgprintk("nonpaging_map: ENOMEM\n");
+ kvm_release_page_clean(page);
return -ENOMEM;
}
@@ -1347,6 +1350,46 @@ static bool last_updated_pte_accessed(struct kvm_vcpu
*vcpu)
return !!(spte && (*spte & PT_ACCESSED_MASK));
}
+static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+ const u8 *new, int bytes)
+{
+ gfn_t gfn;
+ int r;
+ u64 gpte = 0;
+
+ if (bytes != 4 && bytes != 8)
+ return;
+
+ down_read(¤t->mm->mmap_sem);
+ /*
+ * Assume that the pte write on a page table of the same type
+ * as the current vcpu paging mode. This is nearly always true
+ * (might be false while changing modes). Note it is verified later
+ * by update_pte().
+ */
+ if (is_pae(vcpu)) {
+ /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
+ if ((bytes == 4) && (gpa % 4 == 0)) {
+ r = kvm_read_guest(vcpu->kvm, gpa & ~(u64)7, &gpte, 8);
+ if (r)
+ goto out;
+ memcpy((void *)&gpte + (gpa % 8), new, 4);
+ } else if ((bytes == 8) && (gpa % 8 == 0)) {
+ memcpy((void *)&gpte, new, 8);
+ }
+ } else {
+ if ((bytes == 4) && (gpa % 4 == 0))
+ memcpy((void *)&gpte, new, 4);
+ }
+ if (!is_present_pte(gpte))
+ goto out;
+ gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
+ vcpu->arch.update_pte.gfn = gfn;
+ vcpu->arch.update_pte.page = gfn_to_page(vcpu->kvm, gfn);
+out:
+ up_read(¤t->mm->mmap_sem);
+}
+
void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
const u8 *new, int bytes)
{
@@ -1367,6 +1410,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
int npte;
pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes);
+ mmu_guess_page_from_pte_write(vcpu, gpa, new, bytes);
mutex_lock(&vcpu->kvm->lock);
++vcpu->kvm->stat.mmu_pte_write;
kvm_mmu_audit(vcpu, "pre pte write");
@@ -1437,6 +1481,10 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
}
kvm_mmu_audit(vcpu, "post pte write");
mutex_unlock(&vcpu->kvm->lock);
+ if (vcpu->arch.update_pte.page) {
+ kvm_release_page_clean(vcpu->arch.update_pte.page);
+ vcpu->arch.update_pte.page = NULL;
+ }
}
int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 136a65d..5b3ee81 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -245,6 +245,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct
kvm_mmu_page *page,
{
pt_element_t gpte;
unsigned pte_access;
+ struct page *npage;
gpte = *(const pt_element_t *)pte;
if (~gpte & (PT_PRESENT_MASK | PT_ACCESSED_MASK)) {
@@ -256,8 +257,14 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *page,
return;
pgprintk("%s: gpte %llx spte %p\n", __FUNCTION__, (u64)gpte, spte);
pte_access = page->role.access & FNAME(gpte_access)(vcpu, gpte);
+ if (gpte_to_gfn(gpte) != vcpu->arch.update_pte.gfn)
+ return;
+ npage = vcpu->arch.update_pte.page;
+ if (!npage)
+ return;
+ get_page(npage);
mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0,
- gpte & PT_DIRTY_MASK, NULL, gpte_to_gfn(gpte));
+ gpte & PT_DIRTY_MASK, NULL, gpte_to_gfn(gpte), npage);
}
/*
@@ -265,7 +272,8 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct
kvm_mmu_page *page,
*/
static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
struct guest_walker *walker,
- int user_fault, int write_fault, int *ptwrite)
+ int user_fault, int write_fault, int *ptwrite,
+ struct page *page)
{
hpa_t shadow_addr;
int level;
@@ -321,8 +329,10 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
r = kvm_read_guest_atomic(vcpu->kvm,
walker->pte_gpa[level - 2],
&curr_pte, sizeof(curr_pte));
- if (r || curr_pte != walker->ptes[level - 2])
+ if (r || curr_pte != walker->ptes[level - 2]) {
+ kvm_release_page_clean(page);
return NULL;
+ }
}
shadow_addr = __pa(shadow_page->spt);
shadow_pte = shadow_addr | PT_PRESENT_MASK | PT_ACCESSED_MASK
@@ -333,7 +343,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
mmu_set_spte(vcpu, shadow_ent, access, walker->pte_access & access,
user_fault, write_fault,
walker->ptes[walker->level-1] & PT_DIRTY_MASK,
- ptwrite, walker->gfn);
+ ptwrite, walker->gfn, page);
return shadow_ent;
}
@@ -362,6 +372,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t
addr,
u64 *shadow_pte;
int write_pt = 0;
int r;
+ struct page *page;
pgprintk("%s: addr %lx err %x\n", __FUNCTION__, addr, error_code);
kvm_mmu_audit(vcpu, "pre page fault");
@@ -388,9 +399,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t
addr,
return 0;
}
+ down_read(¤t->mm->mmap_sem);
+ page = gfn_to_page(vcpu->kvm, walker.gfn);
+ up_read(¤t->mm->mmap_sem);
+
mutex_lock(&vcpu->kvm->lock);
shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
- &write_pt);
+ &write_pt, page);
pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __FUNCTION__,
shadow_pte, *shadow_pte, write_pt);
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 44b8925..20597bc 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -224,6 +224,11 @@ struct kvm_vcpu_arch {
int last_pt_write_count;
u64 *last_pte_updated;
+ struct {
+ gfn_t gfn; /* presumed gfn during guest pte update */
+ struct page *page; /* page corresponding to that gfn */
+ } update_pte;
+
struct i387_fxsave_struct host_fx_image;
struct i387_fxsave_struct guest_fx_image;
--
1.5.3.7
-------------------------------------------------------------------------
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