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Subject[PATCH 08/12] KVM: MMU: introduce nulls desc
Date
It likes nulls list and we use the pte-list as the nulls which can help us to
detect whether the "desc" is moved to anther rmap then we can re-walk the rmap
if that happened

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
arch/x86/kvm/mmu.c | 35 ++++++++++++++++++++++++++++-------
1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3013bb1..36caf6a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -918,6 +918,24 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
return level - 1;
}

+static void desc_mark_nulls(unsigned long *pte_list, struct pte_list_desc *desc)
+{
+ unsigned long marker;
+
+ marker = (unsigned long)pte_list | 1UL;
+ desc->more = (struct pte_list_desc *)marker;
+}
+
+static bool desc_is_a_nulls(struct pte_list_desc *desc)
+{
+ return (unsigned long)desc & 1;
+}
+
+static unsigned long *desc_get_nulls_value(struct pte_list_desc *desc)
+{
+ return (unsigned long *)((unsigned long)desc & ~1);
+}
+
static int __find_first_free(struct pte_list_desc *desc)
{
int i;
@@ -956,7 +974,7 @@ static int count_spte_number(struct pte_list_desc *desc)

first_free = __find_first_free(desc);

- for (desc_num = 0; desc->more; desc = desc->more)
+ for (desc_num = 0; !desc_is_a_nulls(desc->more); desc = desc->more)
desc_num++;

return first_free + desc_num * PTE_LIST_EXT;
@@ -991,6 +1009,7 @@ static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
desc = mmu_alloc_pte_list_desc(vcpu);
desc->sptes[0] = (u64 *)*pte_list;
desc->sptes[1] = spte;
+ desc_mark_nulls(pte_list, desc);
*pte_list = (unsigned long)desc | 1;
return 1;
}
@@ -1036,7 +1055,7 @@ pte_list_desc_remove_entry(unsigned long *pte_list,
/*
* Only one entry existing but still use a desc to store it?
*/
- WARN_ON(!next_desc);
+ WARN_ON(desc_is_a_nulls(next_desc));

mmu_free_pte_list_desc(first_desc);
first_desc = next_desc;
@@ -1050,7 +1069,7 @@ pte_list_desc_remove_entry(unsigned long *pte_list,
* Only one entry in this desc, move the entry to the head
* then the desc can be freed.
*/
- if (!first_desc->sptes[1] && !first_desc->more) {
+ if (!first_desc->sptes[1] && desc_is_a_nulls(first_desc->more)) {
*pte_list = (unsigned long)first_desc->sptes[0];
mmu_free_pte_list_desc(first_desc);
}
@@ -1077,7 +1096,7 @@ static void pte_list_remove(u64 *spte, unsigned long *pte_list)

rmap_printk("pte_list_remove: %p many->many\n", spte);
desc = (struct pte_list_desc *)(*pte_list & ~1ul);
- while (desc) {
+ while (!desc_is_a_nulls(desc)) {
for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i)
if (desc->sptes[i] == spte) {
pte_list_desc_remove_entry(pte_list,
@@ -1103,11 +1122,13 @@ static void pte_list_walk(unsigned long *pte_list, pte_list_walk_fn fn)
return fn((u64 *)*pte_list);

desc = (struct pte_list_desc *)(*pte_list & ~1ul);
- while (desc) {
+ while (!desc_is_a_nulls(desc)) {
for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i)
fn(desc->sptes[i]);
desc = desc->more;
}
+
+ WARN_ON(desc_get_nulls_value(desc) != pte_list);
}

static unsigned long *__gfn_to_rmap(gfn_t gfn, int level,
@@ -1200,7 +1221,7 @@ static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter)
*/
static u64 *rmap_get_next(struct rmap_iterator *iter)
{
- if (iter->desc) {
+ if (iter->desc && !desc_is_a_nulls(iter->desc)) {
if (iter->pos < PTE_LIST_EXT - 1) {
u64 *sptep;

@@ -1212,7 +1233,7 @@ static u64 *rmap_get_next(struct rmap_iterator *iter)

iter->desc = iter->desc->more;

- if (iter->desc) {
+ if (!desc_is_a_nulls(iter->desc)) {
iter->pos = 0;
/* desc->sptes[0] cannot be NULL */
return iter->desc->sptes[iter->pos];
--
1.8.1.4


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