[PATCH 0/2] Large page fixes

[PATCH 0/2] Large page fixes

[Avi Kivity]

Couple of random large page fixes for review.

Avi Kivity (2):
  KVM: Disable large pages on misaligned memory slots
  KVM: Prevent overflow in largepages calculation

 virt/kvm/kvm_main.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

[PATCH 1/2] KVM: Disable large pages on misaligned memory slots

[Avi Kivity]

If a slots guest physical address and host virtual address unequal (mod
large page size), then we would erronously try to back guest large pages
with host large pages.  Detect this misalignment and diable large page
support for the trouble slot.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 virt/kvm/kvm_main.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9c99307..b9ca73c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1086,7 +1086,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 {
 	int r;
 	gfn_t base_gfn;
-	unsigned long npages;
+	unsigned long npages, ugfn;
 	int largepages;
 	unsigned long i;
 	struct kvm_memory_slot *memslot;
@@ -1177,6 +1177,14 @@ int __kvm_set_memory_region(struct kvm *kvm,
 			new.lpage_info[0].write_count = 1;
 		if ((base_gfn+npages) % KVM_PAGES_PER_HPAGE)
 			new.lpage_info[largepages-1].write_count = 1;
+		ugfn = new.userspace_addr >> PAGE_SHIFT;
+		/*
+		 * If the gfn and userspace address are not aligned wrt each
+		 * other, disable large page support for this slot
+		 */
+		if ((base_gfn ^ ugfn) & (KVM_PAGES_PER_HPAGE - 1))
+			for (i = 0; i < largepages; ++i)
+				new.lpage_info[i].write_count = 1;
 	}
 
 	/* Allocate page dirty bitmap if needed */
-- 
1.6.0.6

[PATCH 2/2] KVM: Prevent overflow in largepages calculation

[Avi Kivity]

If userspace specifies a memory slot that is larger than 8 petabytes, it
could overflow the largepages variable.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 virt/kvm/kvm_main.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b9ca73c..669eb4a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1087,8 +1087,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	int r;
 	gfn_t base_gfn;
 	unsigned long npages, ugfn;
-	int largepages;
-	unsigned long i;
+	unsigned long largepages, i;
 	struct kvm_memory_slot *memslot;
 	struct kvm_memory_slot old, new;
 
-- 
1.6.0.6

Re: [PATCH 0/2] Large page fixes

[Marcelo Tosatti]

On Mon, Jun 08, 2009 at 04:is_largepage_backed00:08PM +0300, Avi Kivity wrote:
> Couple of random large page fixes for review.
> 
> Avi Kivity (2):
>   KVM: Disable large pages on misaligned memory slots
>   KVM: Prevent overflow in largepages calculation
> 
>  virt/kvm/kvm_main.c |   13 ++++++++++---
>  1 files changed, 10 insertions(+), 3 deletions(-)

Looks good, nice catches.

Re: [PATCH 0/2] Large page fixes

[Avi Kivity]

Marcelo Tosatti wrote:
> On Mon, Jun 08, 2009 at 04:is_largepage_backed00:08PM +0300, Avi Kivity wrote:
>   
>> Couple of random large page fixes for review.
>>
>> Avi Kivity (2):
>>   KVM: Disable large pages on misaligned memory slots
>>   KVM: Prevent overflow in largepages calculation
>>
>>  virt/kvm/kvm_main.c |   13 ++++++++++---
>>  1 files changed, 10 insertions(+), 3 deletions(-)
>>     
>
> Looks good, nice catches.
>   

Thanks for the review, I merged those in.

-- 
error compiling committee.c: too many arguments to function