Re: [PATCH] kvm: Fix memory slot generation updates
On Sun, 2012-12-23 at 10:55 +0200, Gleb Natapov wrote:
> On Fri, Dec 21, 2012 at 08:20:16AM -0700, Alex Williamson wrote:
> > Previous patch "kvm: Minor memory slot optimization" overlooked the
> > generation field of the memory slots. Re-using the original memory
> > slots left us with with two slightly different memory slots with the
> > same generation. To fix this, make update_memslots() take a new
> > parameter to specify the last generation. This also makes generation
> > management more explicit to avoid such problems in the future.
> >
> > Reported-by: Takuya Yoshikawa
> > Signed-off-by: Alex Williamson
> Applied, thanks. What about this small cleanup on to of the patch:
Nice cleanup
Reviewed-by: Alex Williamson
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 14cbae8..e45c20c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -702,6 +702,17 @@ static int check_memory_region_flags(struct
> kvm_userspace_memory_region *mem)
> return 0;
> }
>
> +static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
> + struct kvm_memslots *slots, struct kvm_memory_slot *new)
> +{
> + struct kvm_memslots *old_memslots = kvm->memslots;
> +
> + update_memslots(slots, new, kvm->memslots->generation);
> + rcu_assign_pointer(kvm->memslots, slots);
> + synchronize_srcu_expedited(&kvm->srcu);
> + return old_memslots;
> +}
> +
> /*
> * Allocate some memory and give it an address in the guest physical address
> * space.
> @@ -820,11 +831,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
> slot = id_to_memslot(slots, mem->slot);
> slot->flags |= KVM_MEMSLOT_INVALID;
>
> - update_memslots(slots, NULL, kvm->memslots->generation);
> + old_memslots = install_new_memslots(kvm, slots, NULL);
>
> - old_memslots = kvm->memslots;
> - rcu_assign_pointer(kvm->memslots, slots);
> - synchronize_srcu_expedited(&kvm->srcu);
> /* slot was deleted or moved, clear iommu mapping */
> kvm_iommu_unmap_pages(kvm, &old);
> /* From this point no new shadow pages pointing to a deleted,
> @@ -868,10 +876,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> memset(&new.arch, 0, sizeof(new.arch));
> }
>
> - update_memslots(slots, &new, kvm->memslots->generation);
> - old_memslots = kvm->memslots;
> - rcu_assign_pointer(kvm->memslots, slots);
> - synchronize_srcu_expedited(&kvm->srcu);
> + old_memslots = install_new_memslots(kvm, slots, &new);
>
> kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
>
> --
> Gleb.
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Re: [PATCH] kvm: Fix memory slot generation updates
On Sun, 23 Dec 2012 10:55:06 +0200
Gleb Natapov wrote:
> Applied, thanks. What about this small cleanup on to of the patch:
Looks nice! Hope to see this applied as well.
Thanks,
Takuya
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 14cbae8..e45c20c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -702,6 +702,17 @@ static int check_memory_region_flags(struct
> kvm_userspace_memory_region *mem)
> return 0;
> }
>
> +static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
> + struct kvm_memslots *slots, struct kvm_memory_slot *new)
> +{
> + struct kvm_memslots *old_memslots = kvm->memslots;
> +
> + update_memslots(slots, new, kvm->memslots->generation);
> + rcu_assign_pointer(kvm->memslots, slots);
> + synchronize_srcu_expedited(&kvm->srcu);
> + return old_memslots;
> +}
> +
> /*
> * Allocate some memory and give it an address in the guest physical address
> * space.
> @@ -820,11 +831,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
> slot = id_to_memslot(slots, mem->slot);
> slot->flags |= KVM_MEMSLOT_INVALID;
>
> - update_memslots(slots, NULL, kvm->memslots->generation);
> + old_memslots = install_new_memslots(kvm, slots, NULL);
>
> - old_memslots = kvm->memslots;
> - rcu_assign_pointer(kvm->memslots, slots);
> - synchronize_srcu_expedited(&kvm->srcu);
> /* slot was deleted or moved, clear iommu mapping */
> kvm_iommu_unmap_pages(kvm, &old);
> /* From this point no new shadow pages pointing to a deleted,
> @@ -868,10 +876,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> memset(&new.arch, 0, sizeof(new.arch));
> }
>
> - update_memslots(slots, &new, kvm->memslots->generation);
> - old_memslots = kvm->memslots;
> - rcu_assign_pointer(kvm->memslots, slots);
> - synchronize_srcu_expedited(&kvm->srcu);
> + old_memslots = install_new_memslots(kvm, slots, &new);
>
> kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
>
> --
> Gleb.
--
Takuya Yoshikawa
--
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Re: [PATCH] kvm: Fix memory slot generation updates
On Fri, Dec 21, 2012 at 08:20:16AM -0700, Alex Williamson wrote:
> Previous patch "kvm: Minor memory slot optimization" overlooked the
> generation field of the memory slots. Re-using the original memory
> slots left us with with two slightly different memory slots with the
> same generation. To fix this, make update_memslots() take a new
> parameter to specify the last generation. This also makes generation
> management more explicit to avoid such problems in the future.
>
> Reported-by: Takuya Yoshikawa
> Signed-off-by: Alex Williamson
Applied, thanks. What about this small cleanup on to of the patch:
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 14cbae8..e45c20c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -702,6 +702,17 @@ static int check_memory_region_flags(struct
kvm_userspace_memory_region *mem)
return 0;
}
+static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
+ struct kvm_memslots *slots, struct kvm_memory_slot *new)
+{
+ struct kvm_memslots *old_memslots = kvm->memslots;
+
+ update_memslots(slots, new, kvm->memslots->generation);
+ rcu_assign_pointer(kvm->memslots, slots);
+ synchronize_srcu_expedited(&kvm->srcu);
+ return old_memslots;
+}
+
/*
* Allocate some memory and give it an address in the guest physical address
* space.
@@ -820,11 +831,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
slot = id_to_memslot(slots, mem->slot);
slot->flags |= KVM_MEMSLOT_INVALID;
- update_memslots(slots, NULL, kvm->memslots->generation);
+ old_memslots = install_new_memslots(kvm, slots, NULL);
- old_memslots = kvm->memslots;
- rcu_assign_pointer(kvm->memslots, slots);
- synchronize_srcu_expedited(&kvm->srcu);
/* slot was deleted or moved, clear iommu mapping */
kvm_iommu_unmap_pages(kvm, &old);
/* From this point no new shadow pages pointing to a deleted,
@@ -868,10 +876,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
memset(&new.arch, 0, sizeof(new.arch));
}
- update_memslots(slots, &new, kvm->memslots->generation);
- old_memslots = kvm->memslots;
- rcu_assign_pointer(kvm->memslots, slots);
- synchronize_srcu_expedited(&kvm->srcu);
+ old_memslots = install_new_memslots(kvm, slots, &new);
kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
--
Gleb.
--
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[PATCH] kvm: Fix memory slot generation updates
Previous patch "kvm: Minor memory slot optimization" overlooked the
generation field of the memory slots. Re-using the original memory
slots left us with with two slightly different memory slots with the
same generation. To fix this, make update_memslots() take a new
parameter to specify the last generation. This also makes generation
management more explicit to avoid such problems in the future.
Reported-by: Takuya Yoshikawa
Signed-off-by: Alex Williamson
---
include/linux/kvm_host.h |3 ++-
virt/kvm/kvm_main.c |9 +
2 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 32fdc45..cbe0d68 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -428,7 +428,8 @@ void kvm_exit(void);
void kvm_get_kvm(struct kvm *kvm);
void kvm_put_kvm(struct kvm *kvm);
-void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new);
+void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,
+u64 last_generation);
static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
{
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bd31096..14cbae8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -672,7 +672,8 @@ static void sort_memslots(struct kvm_memslots *slots)
slots->id_to_index[slots->memslots[i].id] = i;
}
-void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new)
+void update_memslots(struct kvm_memslots *slots, struct kvm_memory_slot *new,
+u64 last_generation)
{
if (new) {
int id = new->id;
@@ -684,7 +685,7 @@ void update_memslots(struct kvm_memslots *slots, struct
kvm_memory_slot *new)
sort_memslots(slots);
}
- slots->generation++;
+ slots->generation = last_generation + 1;
}
static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
@@ -819,7 +820,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
slot = id_to_memslot(slots, mem->slot);
slot->flags |= KVM_MEMSLOT_INVALID;
- update_memslots(slots, NULL);
+ update_memslots(slots, NULL, kvm->memslots->generation);
old_memslots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
@@ -867,7 +868,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
memset(&new.arch, 0, sizeof(new.arch));
}
- update_memslots(slots, &new);
+ update_memslots(slots, &new, kvm->memslots->generation);
old_memslots = kvm->memslots;
rcu_assign_pointer(kvm->memslots, slots);
synchronize_srcu_expedited(&kvm->srcu);
--
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