Bump the size of the sptes array by one and use the raw level of the
SPTE to index into the sptes array. Using the SPTE level directly
improves readability by eliminating the need to reason out why the level
is being adjusted when indexing the array. The array is on the stack
and is not explicitly initialized; bumping its size is nothing more than
a superficial adjustment to the stack frame.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-4-seanjc@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Get the so called "root" level from the low level shadow page table
walkers instead of manually attempting to calculate it higher up the
stack, e.g. in get_mmio_spte(). When KVM is using PAE shadow paging,
the starting level of the walk, from the callers perspective, is not
the CR3 root but rather the PDPTR "root". Checking for reserved bits
from the CR3 root causes get_mmio_spte() to consume uninitialized stack
data due to indexing into sptes[] for a level that was not filled by
get_walk(). This can result in false positives and/or negatives
depending on what garbage happens to be on the stack.
Opportunistically nuke a few extra newlines.
Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Reported-by: Richard Herbert <rherbert@sympatico.ca>
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Return -1 from the get_walk() helpers if the shadow walk doesn't fill at
least one spte, which can theoretically happen if the walk hits a
not-present PDPTR. Returning the root level in such a case will cause
get_mmio_spte() to return garbage (uninitialized stack data). In
practice, such a scenario should be impossible as KVM shouldn't get a
reserved-bit page fault with a not-present PDPTR.
Note, using mmu->root_level in get_walk() is wrong for other reasons,
too, but that's now a moot point.
Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In the TDP MMU, use shadow_phys_bits to dermine the maximum possible GFN
mapped in the guest for zapping operations. boot_cpu_data.x86_phys_bits
may be reduced in the case of HW features that steal HPA bits for other
purposes. However, this doesn't necessarily reduce GPA space that can be
accessed via TDP. So zap based on a maximum gfn calculated with MAXPHYADDR
retrieved from CPUID. This is already stored in shadow_phys_bits, so use
it instead of x86_phys_bits.
Fixes: faaf05b00a ("kvm: x86/mmu: Support zapping SPTEs in the TDP MMU")
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-Id: <20201203231120.27307-1-rick.p.edgecombe@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add an extremely verbose trace point to the TDP MMU to log all SPTE
changes, regardless of callstack / motivation. This is useful when a
complete picture of the paging structure is needed or a change cannot be
explained with the other, existing trace points.
Tested: ran the demand paging selftest on an Intel Skylake machine with
all the trace points used by the TDP MMU enabled and observed
them firing with expected values.
This patch can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/3813
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201027175944.1183301-2-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU was initially implemented without some of the usual
tracepoints found in mmu.c. Correct this discrepancy by adding the
missing trace points to the TDP MMU.
Tested: ran the demand paging selftest on an Intel Skylake machine with
all the trace points used by the TDP MMU enabled and observed
them firing with expected values.
This patch can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/3812
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201027175944.1183301-1-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch is heavily based on previous work from Lei Cao
<lei.cao@stratus.com> and Paolo Bonzini <pbonzini@redhat.com>. [1]
KVM currently uses large bitmaps to track dirty memory. These bitmaps
are copied to userspace when userspace queries KVM for its dirty page
information. The use of bitmaps is mostly sufficient for live
migration, as large parts of memory are be dirtied from one log-dirty
pass to another. However, in a checkpointing system, the number of
dirty pages is small and in fact it is often bounded---the VM is
paused when it has dirtied a pre-defined number of pages. Traversing a
large, sparsely populated bitmap to find set bits is time-consuming,
as is copying the bitmap to user-space.
A similar issue will be there for live migration when the guest memory
is huge while the page dirty procedure is trivial. In that case for
each dirty sync we need to pull the whole dirty bitmap to userspace
and analyse every bit even if it's mostly zeros.
The preferred data structure for above scenarios is a dense list of
guest frame numbers (GFN). This patch series stores the dirty list in
kernel memory that can be memory mapped into userspace to allow speedy
harvesting.
This patch enables dirty ring for X86 only. However it should be
easily extended to other archs as well.
[1] https://patchwork.kernel.org/patch/10471409/
Signed-off-by: Lei Cao <lei.cao@stratus.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20201001012222.5767-1-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In some cases where shadow paging is in use, the root page will
be either mmu->pae_root or vcpu->arch.mmu->lm_root. Then it will
not have an associated struct kvm_mmu_page, because it is allocated
with alloc_page instead of kvm_mmu_alloc_page.
Just return false quickly from is_tdp_mmu_root if the TDP MMU is
not in use, which also includes the case where shadow paging is
enabled.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Replace a modulo operator with the more common pattern for computing the
gfn "offset" of a huge page to fix an i386 build error.
arch/x86/kvm/mmu/tdp_mmu.c:212: undefined reference to `__umoddi3'
In fact, almost all of tdp_mmu.c can be elided on 32-bit builds, but
that is a much larger patch.
Fixes: 2f2fad0897 ("kvm: x86/mmu: Add functions to handle changed TDP SPTEs")
Reported-by: Daniel Díaz <daniel.diaz@linaro.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201024031150.9318-1-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When KVM maps a largepage backed region at a lower level in order to
make it executable (i.e. NX large page shattering), it reduces the TLB
performance of that region. In order to avoid making this degradation
permanent, KVM must periodically reclaim shattered NX largepages by
zapping them and allowing them to be rebuilt in the page fault handler.
With this patch, the TDP MMU does not respect KVM's rate limiting on
reclaim. It traverses the entire TDP structure every time. This will be
addressed in a future patch.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-21-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to support MMIO, KVM must be able to walk the TDP paging
structures to find mappings for a given GFN. Support this walk for
the TDP MMU.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
v2: Thanks to Dan Carpenter and kernel test robot for finding that root
was used uninitialized in get_mmio_spte.
Signed-off-by: Ben Gardon <bgardon@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <20201014182700.2888246-19-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
To support nested virtualization, KVM will sometimes need to write
protect pages which are part of a shadowed paging structure or are not
writable in the shadowed paging structure. Add a function to write
protect GFN mappings for this purpose.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-18-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Dirty logging ultimately breaks down MMU mappings to 4k granularity.
When dirty logging is no longer needed, these granaular mappings
represent a useless performance penalty. When dirty logging is disabled,
search the paging structure for mappings that could be re-constituted
into a large page mapping. Zap those mappings so that they can be
faulted in again at a higher mapping level.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-17-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Dirty logging is a key feature of the KVM MMU and must be supported by
the TDP MMU. Add support for both the write protection and PML dirty
logging modes.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-16-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
a hook and handle the change_pte MMU notifier.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-15-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. The
main Linux MM uses the access tracking MMU notifiers for swap and other
features. Add hooks to handle the test/flush HVA (range) family of
MMU notifiers.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-14-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In order to interoperate correctly with the rest of KVM and other Linux
subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
hooks to handle the invalidate range family of MMU notifiers.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-13-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Attach struct kvm_mmu_pages to every page in the TDP MMU to track
metadata, facilitate NX reclaim, and enable inproved parallelism of MMU
operations in future patches.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-12-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add functions to handle page faults in the TDP MMU. These page faults
are currently handled in much the same way as the x86 shadow paging
based MMU, however the ordering of some operations is slightly
different. Future patches will add eager NX splitting, a fast page fault
handler, and parallel page faults.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add functions to zap SPTEs to the TDP MMU. These are needed to tear down
TDP MMU roots properly and implement other MMU functions which require
tearing down mappings. Future patches will add functions to populate the
page tables, but as for this patch there will not be any work for these
functions to do.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The existing bookkeeping done by KVM when a PTE is changed is spread
around several functions. This makes it difficult to remember all the
stats, bitmaps, and other subsystems that need to be updated whenever a
PTE is modified. When a non-leaf PTE is marked non-present or becomes a
leaf PTE, page table memory must also be freed. To simplify the MMU and
facilitate the use of atomic operations on SPTEs in future patches, create
functions to handle some of the bookkeeping required as a result of
a change.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU must be able to allocate paging structure root pages and track
the usage of those pages. Implement a similar, but separate system for root
page allocation to that of the x86 shadow paging implementation. When
future patches add synchronization model changes to allow for parallel
page faults, these pages will need to be handled differently from the
x86 shadow paging based MMU's root pages.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TDP MMU offers an alternative mode of operation to the x86 shadow
paging based MMU, optimized for running an L1 guest with TDP. The TDP MMU
will require new fields that need to be initialized and torn down. Add
hooks into the existing KVM MMU initialization process to do that
initialization / cleanup. Currently the initialization and cleanup
fucntions do not do very much, however more operations will be added in
future patches.
Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.
This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201014182700.2888246-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
