Sorry, the title is not clear enough.
This is the v2 which fixes the issue pointed out by David:
" the generation number actually decreases."
Please review.
On 08/14/2014 03:01 PM, Xiao Guangrong wrote:
> We may cache the current mmio generation number and stale memslot info
> into spte, like this scenarioļ¼
>
> CPU 0 CPU 1
> page fault: add a new memslot
> read memslot and detecting its a mmio access
> update memslots
> update generation number
> read generation number
> cache the gpa and current gen number into spte
>
> So, if guest accesses the gpa later, it will generate a incorrect
> mmio exit
>
> This patch fixes it by updating the generation number after
> synchronize_srcu_expedited() that makes sure the generation
> number updated only if memslots update is finished
>
> Cc: sta...@vger.kernel.org
> Cc: David Matlack <dmatl...@google.com>
> Signed-off-by: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com>
> ---
> virt/kvm/kvm_main.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 33712fb..bb40df3 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -96,7 +96,7 @@ static void hardware_disable_all(void);
>
> static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
> static void update_memslots(struct kvm_memslots *slots,
> - struct kvm_memory_slot *new, u64 last_generation);
> + struct kvm_memory_slot *new);
>
> static void kvm_release_pfn_dirty(pfn_t pfn);
> static void mark_page_dirty_in_slot(struct kvm *kvm,
> @@ -687,8 +687,7 @@ static void sort_memslots(struct kvm_memslots *slots)
> }
>
> static void update_memslots(struct kvm_memslots *slots,
> - struct kvm_memory_slot *new,
> - u64 last_generation)
> + struct kvm_memory_slot *new)
> {
> if (new) {
> int id = new->id;
> @@ -699,8 +698,6 @@ static void update_memslots(struct kvm_memslots *slots,
> if (new->npages != npages)
> sort_memslots(slots);
> }
> -
> - slots->generation = last_generation + 1;
> }
>
> static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
> @@ -722,9 +719,12 @@ static struct kvm_memslots *install_new_memslots(struct
> kvm *kvm,
> {
> struct kvm_memslots *old_memslots = kvm->memslots;
>
> - update_memslots(slots, new, kvm->memslots->generation);
> + /* ensure generation number is always increased. */
> + slots->generation = old_memslots->generation;
> + update_memslots(slots, new);
> rcu_assign_pointer(kvm->memslots, slots);
> synchronize_srcu_expedited(&kvm->srcu);
> + slots->generation++;
>
> kvm_arch_memslots_updated(kvm);
>
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