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Subject[PATCH 3.17 018/146] KVM: do not bias the generation number in kvm_current_mmio_generation
Date
3.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@redhat.com>

commit 00f034a12fdd81210d58116326d92780aac5c238 upstream.

The next patch will give a meaning (a la seqcount) to the low bit of the
generation number. Ensure that it matches between kvm->memslots->generation
and kvm_current_mmio_generation().

Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/mmu.c | 7 +------
virt/kvm/kvm_main.c | 7 +++++++
2 files changed, 8 insertions(+), 6 deletions(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -240,12 +240,7 @@ static unsigned int get_mmio_spte_genera

static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
{
- /*
- * Init kvm generation close to MMIO_MAX_GEN to easily test the
- * code of handling generation number wrap-around.
- */
- return (kvm_memslots(kvm)->generation +
- MMIO_MAX_GEN - 150) & MMIO_GEN_MASK;
+ return kvm_memslots(kvm)->generation & MMIO_GEN_MASK;
}

static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn,
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -474,6 +474,13 @@ static struct kvm *kvm_create_vm(unsigne
kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
if (!kvm->memslots)
goto out_err_no_srcu;
+
+ /*
+ * Init kvm generation close to the maximum to easily test the
+ * code of handling generation number wrap-around.
+ */
+ kvm->memslots->generation = -150;
+
kvm_init_memslots_id(kvm);
if (init_srcu_struct(&kvm->srcu))
goto out_err_no_srcu;



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