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Subject[PATCH 5.0 227/238] KVM: x86/mmu: Detect MMIO generation wrap in any address space
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

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

From: Sean Christopherson <sean.j.christopherson@intel.com>

commit e1359e2beb8b0a1188abc997273acbaedc8ee791 upstream.

The check to detect a wrap of the MMIO generation explicitly looks for a
generation number of zero. Now that unique memslots generation numbers
are assigned to each address space, only address space 0 will get a
generation number of exactly zero when wrapping. E.g. when address
space 1 goes from 0x7fffe to 0x80002, the MMIO generation number will
wrap to 0x2. Adjust the MMIO generation to strip the address space
modifier prior to checking for a wrap.

Fixes: 4bd518f1598d ("KVM: use separate generations for each address space")
Cc: <stable@vger.kernel.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/mmu.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5893,11 +5893,28 @@ static bool kvm_has_zapped_obsolete_page

void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
{
+ gen &= MMIO_GEN_MASK;
+
+ /*
+ * Shift to eliminate the "update in-progress" flag, which isn't
+ * included in the spte's generation number.
+ */
+ gen >>= 1;
+
+ /*
+ * Generation numbers are incremented in multiples of the number of
+ * address spaces in order to provide unique generations across all
+ * address spaces. Strip what is effectively the address space
+ * modifier prior to checking for a wrap of the MMIO generation so
+ * that a wrap in any address space is detected.
+ */
+ gen &= ~((u64)KVM_ADDRESS_SPACE_NUM - 1);
+
/*
- * The very rare case: if the generation-number is round,
+ * The very rare case: if the MMIO generation number has wrapped,
* zap all shadow pages.
*/
- if (unlikely((gen & MMIO_GEN_MASK) == 0)) {
+ if (unlikely(gen == 0)) {
kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
kvm_mmu_invalidate_zap_all_pages(kvm);
}

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