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  1. 03 9月, 2014 4 次提交
    • T
      KVM: mmio: cleanup kvm_set_mmio_spte_mask · d1431483
      由 Tiejun Chen 提交于 
      Just reuse rsvd_bits() inside kvm_set_mmio_spte_mask()
for slightly better code.
Signed-off-by: NTiejun Chen <tiejun.chen@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      d1431483
    • D
      kvm: x86: fix stale mmio cache bug · 56f17dd3
      由 David Matlack 提交于 
      The following events can lead to an incorrect KVM_EXIT_MMIO bubbling
up to userspace:

(1) Guest accesses gpa X without a memory slot. The gfn is cached in
struct kvm_vcpu_arch (mmio_gfn). On Intel EPT-enabled hosts, KVM sets
the SPTE write-execute-noread so that future accesses cause
EPT_MISCONFIGs.

(2) Host userspace creates a memory slot via KVM_SET_USER_MEMORY_REGION
covering the page just accessed.

(3) Guest attempts to read or write to gpa X again. On Intel, this
generates an EPT_MISCONFIG. The memory slot generation number that
was incremented in (2) would normally take care of this but we fast
path mmio faults through quickly_check_mmio_pf(), which only checks
the per-vcpu mmio cache. Since we hit the cache, KVM passes a
KVM_EXIT_MMIO up to userspace.

This patch fixes the issue by using the memslot generation number
to validate the mmio cache.

Cc: stable@vger.kernel.org
Signed-off-by: NDavid Matlack <dmatlack@google.com>
[xiaoguangrong: adjust the code to make it simpler for stable-tree fix.]
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: NDavid Matlack <dmatlack@google.com>
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Tested-by: NDavid Matlack <dmatlack@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      56f17dd3
    • D
      kvm: fix potentially corrupt mmio cache · ee3d1570
      由 David Matlack 提交于 
      vcpu exits and memslot mutations can run concurrently as long as the
vcpu does not aquire the slots mutex. Thus it is theoretically possible
for memslots to change underneath a vcpu that is handling an exit.

If we increment the memslot generation number again after
synchronize_srcu_expedited(), vcpus can safely cache memslot generation
without maintaining a single rcu_dereference through an entire vm exit.
And much of the x86/kvm code does not maintain a single rcu_dereference
of the current memslots during each exit.

We can prevent the following case:

   vcpu (CPU 0)                             | thread (CPU 1)
--------------------------------------------+--------------------------
1  vm exit                                  |
2  srcu_read_unlock(&kvm->srcu)             |
3  decide to cache something based on       |
     old memslots                           |
4                                           | change memslots
                                            | (increments generation)
5                                           | synchronize_srcu(&kvm->srcu);
6  retrieve generation # from new memslots  |
7  tag cache with new memslot generation    |
8  srcu_read_unlock(&kvm->srcu)             |
...                                         |
   <action based on cache occurs even       |
    though the caching decision was based   |
    on the old memslots>                    |
...                                         |
   <action *continues* to occur until next  |
    memslot generation change, which may    |
    be never>                               |
                                            |

By incrementing the generation after synchronizing with kvm->srcu readers,
we ensure that the generation retrieved in (6) will become invalid soon
after (8).

Keeping the existing increment is not strictly necessary, but we
do keep it and just move it for consistency from update_memslots to
install_new_memslots.  It invalidates old cached MMIOs immediately,
instead of having to wait for the end of synchronize_srcu_expedited,
which makes the code more clearly correct in case CPU 1 is preempted
right after synchronize_srcu() returns.

To avoid halving the generation space in SPTEs, always presume that the
low bit of the generation is zero when reconstructing a generation number
out of an SPTE.  This effectively disables MMIO caching in SPTEs during
the call to synchronize_srcu_expedited.  Using the low bit this way is
somewhat like a seqcount---where the protected thing is a cache, and
instead of retrying we can simply punt if we observe the low bit to be 1.

Cc: stable@vger.kernel.org
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: NDavid Matlack <dmatlack@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      ee3d1570
    • P
      KVM: do not bias the generation number in kvm_current_mmio_generation · 00f034a1
      由 Paolo Bonzini 提交于 
      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().

Cc: stable@vger.kernel.org
Reviewed-by: NDavid Matlack <dmatlack@google.com>
Reviewed-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      00f034a1
  3. 30 8月, 2014 1 次提交
  5. 29 8月, 2014 7 次提交
  7. 25 8月, 2014 1 次提交
  9. 22 8月, 2014 5 次提交
  11. 21 8月, 2014 1 次提交
  13. 20 8月, 2014 4 次提交
  15. 19 8月, 2014 10 次提交
  17. 09 8月, 2014 1 次提交
  19. 05 8月, 2014 3 次提交
  21. 31 7月, 2014 1 次提交
  23. 30 7月, 2014 1 次提交
  25. 28 7月, 2014 1 次提交