queue-4.19/kvm-x86-mmu-detect-mmio-generation-wrap-in-any-address-space.patch

   1 From e1359e2beb8b0a1188abc997273acbaedc8ee791 Mon Sep 17 00:00:00 2001
   2 From: Sean Christopherson <sean.j.christopherson@intel.com>
   3 Date: Tue, 5 Feb 2019 13:01:12 -0800
   4 Subject: KVM: x86/mmu: Detect MMIO generation wrap in any address space
   5
   6 From: Sean Christopherson <sean.j.christopherson@intel.com>
   7
   8 commit e1359e2beb8b0a1188abc997273acbaedc8ee791 upstream.
   9
  10 The check to detect a wrap of the MMIO generation explicitly looks for a
  11 generation number of zero.  Now that unique memslots generation numbers
  12 are assigned to each address space, only address space 0 will get a
  13 generation number of exactly zero when wrapping.  E.g. when address
  14 space 1 goes from 0x7fffe to 0x80002, the MMIO generation number will
  15 wrap to 0x2.  Adjust the MMIO generation to strip the address space
  16 modifier prior to checking for a wrap.
  17
  18 Fixes: 4bd518f1598d ("KVM: use separate generations for each address space")
  19 Cc: <stable@vger.kernel.org>
  20 Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
  21 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23
  24 ---
  25  arch/x86/kvm/mmu.c |   21 +++++++++++++++++++--
  26  1 file changed, 19 insertions(+), 2 deletions(-)
  27
  28 --- a/arch/x86/kvm/mmu.c
  29 +++ b/arch/x86/kvm/mmu.c
  30 @@ -5776,11 +5776,28 @@ static bool kvm_has_zapped_obsolete_page
  31
  32  void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
  33  {
  34 +       gen &= MMIO_GEN_MASK;
  35 +
  36 +       /*
  37 +        * Shift to eliminate the "update in-progress" flag, which isn't
  38 +        * included in the spte's generation number.
  39 +        */
  40 +       gen >>= 1;
  41 +
  42 +       /*
  43 +        * Generation numbers are incremented in multiples of the number of
  44 +        * address spaces in order to provide unique generations across all
  45 +        * address spaces.  Strip what is effectively the address space
  46 +        * modifier prior to checking for a wrap of the MMIO generation so
  47 +        * that a wrap in any address space is detected.
  48 +        */
  49 +       gen &= ~((u64)KVM_ADDRESS_SPACE_NUM - 1);
  50 +
  51         /*
  52 -        * The very rare case: if the generation-number is round,
  53 +        * The very rare case: if the MMIO generation number has wrapped,
  54          * zap all shadow pages.
  55          */
  56 -       if (unlikely((gen & MMIO_GEN_MASK) == 0)) {
  57 +       if (unlikely(gen == 0)) {
  58                 kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
  59                 kvm_mmu_invalidate_zap_all_pages(kvm);
  60         }