This patch cleanups rmap_write_protect() as follows:
1.
The BUG_ON(!spte)'s right after while(spte) have been there unchanged for
a long time. Since we don't see any special reason why we do this double
check, we remove these BUG_ON's.
2.
In the case of Y and Z are single-bit-set masks,
Y: PT_PAGE_SIZE_MASK (1ULL << 7)
Z: PT_PRESENT_MASK (1ULL << 0)
checking the following two conditions
(X & Z)
(X & (Y|Z)) == (Y|Z)
is logically equivalent to checking
(X & Z)
(X & Y)
meaning that X has the both bits represented by Y and Z set.
Considering the nature of these bit masks, the condition that these masks
are single-bit-set will not change. So this patch replaces the second
check to simpler one to make what we are checking clearer.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
---
arch/x86/kvm/mmu.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 56da796..df8c09d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -740,7 +740,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
spte = rmap_next(kvm, rmapp, NULL);
while (spte) {
- BUG_ON(!spte);
BUG_ON(!(*spte & PT_PRESENT_MASK));
rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
if (is_writable_pte(*spte)) {
@@ -763,9 +762,8 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
rmapp = gfn_to_rmap(kvm, gfn, i);
spte = rmap_next(kvm, rmapp, NULL);
while (spte) {
- BUG_ON(!spte);
BUG_ON(!(*spte & PT_PRESENT_MASK));
- BUG_ON((*spte & (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK)) != (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK));
+ BUG_ON(!(*spte & PT_PAGE_SIZE_MASK));
pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);
if (is_writable_pte(*spte)) {
drop_spte(kvm, spte,
--
1.7.0.4
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
