To reduce the impact of disabling dirty logging, change the TDP MMU
function which zaps collapsible SPTEs to run under the MMU read lock.
This way, page faults on zapped SPTEs can proceed in parallel with
kvm_mmu_zap_collapsible_sptes.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-11-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

To reduce lock contention and interference with page fault handlers,
allow the TDP MMU function to zap a GFN range to operate under the MMU
read lock.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-10-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

kvm_tdp_mmu_put_root and kvm_tdp_mmu_free_root are always called
together, so merge the functions to simplify TDP MMU root refcounting /
freeing.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-5-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The TDP MMU is almost the only user of kvm_mmu_get_root and
kvm_mmu_put_root. There is only one use of put_root in mmu.c for the
legacy / shadow MMU. Open code that one use and move the get / put
functions to the TDP MMU so they can be extended in future commits.

No functional change intended.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-3-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

kvm_tdp_mmu_zap_collapsible_sptes unnecessarily removes the const
qualifier from its memlsot argument, leading to a compiler warning. Add
the const annotation and pass it to subsequent functions.
Signed-off-by: NBen Gardon <bgardon@google.com>
Message-Id: <20210401233736.638171-2-bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the hva->gfn lookup for MMU notifiers into common code.  Every arch
does a similar lookup, and some arch code is all but identical across
multiple architectures.

In addition to consolidating code, this will allow introducing
optimizations that will benefit all architectures without incurring
multiple walks of the memslots, e.g. by taking mmu_lock if and only if a
relevant range exists in the memslots.

The use of __always_inline to avoid indirect call retpolines, as done by
x86, may also benefit other architectures.

Consolidating the lookups also fixes a wart in x86, where the legacy MMU
and TDP MMU each do their own memslot walks.

Lastly, future enhancements to the memslot implementation, e.g. to add an
interval tree to track host address, will need to touch far less arch
specific code.

MIPS, PPC, and arm64 will be converted one at a time in future patches.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210402005658.3024832-3-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

memslots are stored in RCU and there should be no need to
change them.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

When using manual protection of dirty pages, it is not necessary
to protect nested page tables down to the 4K level; instead KVM
can protect only hugepages in order to split them lazily, and
delay write protection at 4K-granularity until KVM_CLEAR_DIRTY_LOG.
This was overlooked in the TDP MMU, so do it there as well.

Fixes: a6a0b05d ("kvm: x86/mmu: Support dirty logging for the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Reviewed-by: NKeqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Remove x86's trace_kvm_age_page() tracepoint.  It's mostly redundant with
the common trace_kvm_age_hva() tracepoint, and if there is a need for the
extra details, e.g. gfn, referenced, etc... those details should be added
to the common tracepoint so that all architectures and MMUs benefit from
the info.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-19-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Pass the address space ID to TDP MMU's primary "zap gfn range" helper to
allow the MMU notifier paths to iterate over memslots exactly once.
Currently, both the legacy MMU and TDP MMU iterate over memslots when
looking for an overlapping hva range, which can be quite costly if there
are a large number of memslots.

Add a "flush" parameter so that iterating over multiple address spaces
in the caller will continue to do the right thing when yielding while a
flush is pending from a previous address space.

Note, this also has a functional change in the form of coalescing TLB
flushes across multiple address spaces in kvm_zap_gfn_range(), and also
optimizes the TDP MMU to utilize range-based flushing when running as L1
with Hyper-V enlightenments.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-6-seanjc@google.com>
[Keep separate for loops to prepare for other incoming patches. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Gather pending TLB flushes across both address spaces when zapping a
given gfn range.  This requires feeding "flush" back into subsequent
calls, but on the plus side sets the stage for further batching
between the legacy MMU and TDP MMU.  It also allows refactoring the
address space iteration to cover the legacy and TDP MMUs without
introducing truly ugly code.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-5-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Gather pending TLB flushes across both the legacy and TDP MMUs when
zapping collapsible SPTEs to avoid multiple flushes if both the legacy
MMU (for nested guests) and TDP MMU have mappings for the memslot.

Note, this also optimizes the TDP MMU to flush only the relevant range
when running as L1 with Hyper-V enlightenments.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-4-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Place the onus on the caller of slot_handle_*() to flush the TLB, rather
than handling the flush in the helper, and rename parameters accordingly.
This will allow future patches to coalesce flushes between address spaces
and between the legacy and TDP MMUs.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-3-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

On SVM, reading PDPTRs might access guest memory, which might fault
and thus might sleep.  On the other hand, it is not possible to
release the lock after make_mmu_pages_available has been called.

Therefore, push the call to make_mmu_pages_available and the
mmu_lock critical section within mmu_alloc_direct_roots and
mmu_alloc_shadow_roots.
Reported-by: NWanpeng Li <wanpengli@tencent.com>
Co-developed-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Prevent the TDP MMU from yielding when zapping a gfn range during NX
page recovery.  If a flush is pending from a previous invocation of the
zapping helper, either in the TDP MMU or the legacy MMU, but the TDP MMU
has not accumulated a flush for the current invocation, then yielding
will release mmu_lock with stale TLB entries.

That being said, this isn't technically a bug fix in the current code, as
the TDP MMU will never yield in this case.  tdp_mmu_iter_cond_resched()
will yield if and only if it has made forward progress, as defined by the
current gfn vs. the last yielded (or starting) gfn.  Because zapping a
single shadow page is guaranteed to (a) find that page and (b) step
sideways at the level of the shadow page, the TDP iter will break its loop
before getting a chance to yield.

But that is all very, very subtle, and will break at the slightest sneeze,
e.g. zapping while holding mmu_lock for read would break as the TDP MMU
wouldn't be guaranteed to see the present shadow page, and thus could step
sideways at a lower level.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210325200119.1359384-4-seanjc@google.com>
[Add lockdep assertion. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Honor the "flush needed" return from kvm_tdp_mmu_zap_gfn_range(), which
does the flush itself if and only if it yields (which it will never do in
this particular scenario), and otherwise expects the caller to do the
flush.  If pages are zapped from the TDP MMU but not the legacy MMU, then
no flush will occur.

Fixes: 29cf0f50 ("kvm: x86/mmu: NX largepage recovery for TDP MMU")
Cc: stable@vger.kernel.org
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210325200119.1359384-3-seanjc@google.com>
Reviewed-by: NBen Gardon <bgardon@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Set the PAE roots used as decrypted to play nice with SME when KVM is
using shadow paging.  Explicitly skip setting the C-bit when loading
CR3 for PAE shadow paging, even though it's completely ignored by the
CPU.  The extra documentation is nice to have.

Note, there are several subtleties at play with NPT.  In addition to
legacy shadow paging, the PAE roots are used for SVM's NPT when either
KVM is 32-bit (uses PAE paging) or KVM is 64-bit and shadowing 32-bit
NPT.  However, 32-bit Linux, and thus KVM, doesn't support SME.  And
64-bit KVM can happily set the C-bit in CR3.  This also means that
keeping __sme_set(root) for 32-bit KVM when NPT is enabled is
conceptually wrong, but functionally ok since SME is 64-bit only.
Leave it as is to avoid unnecessary pollution.

Fixes: d0ec49d4 ("kvm/x86/svm: Support Secure Memory Encryption within KVM")
Cc: stable@vger.kernel.org
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210309224207.1218275-5-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Use '0' to denote an invalid pae_root instead of '0' or INVALID_PAGE.
Unlike root_hpa, the pae_roots hold permission bits and thus are
guaranteed to be non-zero.  Having to deal with both values leads to
bugs, e.g. failing to set back to INVALID_PAGE, warning on the wrong
value, etc...
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210309224207.1218275-4-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Debugging unexpected reserved bit page faults sucks.  Dump the reserved
bits that (likely) caused the page fault to make debugging suck a little
less.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-25-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Make the location of the HOST_WRITABLE and MMU_WRITABLE configurable for
a given KVM instance.  This will allow EPT to use high available bits,
which in turn will free up bit 11 for a constant MMU_PRESENT bit.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-19-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Squish all the code for (re)setting the various SPTE masks into one
location.  With the split code, it's not at all clear that the masks are
set once during module initialization.  This will allow a future patch to
clean up initialization of the masks without shuffling code all over
tarnation.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-17-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move kvm_mmu_set_mask_ptes() into mmu.c as prep for future cleanup of the
mask initialization code.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-16-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Stop tagging MMIO SPTEs with specific available bits and instead detect
MMIO SPTEs by checking for their unique SPTE value.  The value is
guaranteed to be unique on shadow paging and NPT as setting reserved
physical address bits on any other type of SPTE would consistute a KVM
bug.  Ditto for EPT, as creating a WX non-MMIO would also be a bug.

Note, this approach is also future-compatibile with TDX, which will need
to reflect MMIO EPT violations as #VEs into the guest.  To create an EPT
violation instead of a misconfig, TDX EPTs will need to have RWX=0,  But,
MMIO SPTEs will also be the only case where KVM clears SUPPRESS_VE, so
MMIO SPTEs will still be guaranteed to have a unique value within a given
MMU context.

The main motivation is to make it easier to reason about which types of
SPTEs use which available bits.  As a happy side effect, this frees up
two more bits for storing the MMIO generation.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-11-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The value returned by make_mmio_spte() is a SPTE, it is not a mask.
Name it accordingly.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-10-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Now that it should be impossible to convert a valid SPTE to an MMIO SPTE,
handle MMIO SPTEs early in mmu_set_spte() without going through
set_spte() and all the logic for removing an existing, valid SPTE.
The other caller of set_spte(), FNAME(sync_page)(), explicitly handles
MMIO SPTEs prior to calling set_spte().

This simplifies mmu_set_spte() and set_spte(), and also "fixes" an oddity
where MMIO SPTEs are traced by both trace_kvm_mmu_set_spte() and
trace_mark_mmio_spte().

Note, mmu_spte_set() will WARN if this new approach causes KVM to create
an MMIO SPTE overtop a valid SPTE.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-8-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

If MMIO caching is disabled, e.g. when using shadow paging on CPUs with
52 bits of PA space, go straight to MMIO emulation and don't install an
MMIO SPTE.  The SPTE will just generate a !PRESENT #PF, i.e. can't
actually accelerate future MMIO.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-7-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Retry page faults (re-enter the guest) that hit an invalid memslot
instead of treating the memslot as not existing, i.e. handling the
page fault as an MMIO access.  When deleting a memslot, SPTEs aren't
zapped and the TLBs aren't flushed until after the memslot has been
marked invalid.

Handling the invalid slot as MMIO means there's a small window where a
page fault could replace a valid SPTE with an MMIO SPTE.  The legacy
MMU handles such a scenario cleanly, but the TDP MMU assumes such
behavior is impossible (see the BUG() in __handle_changed_spte()).
There's really no good reason why the legacy MMU should allow such a
scenario, and closing this hole allows for additional cleanups.

Fixes: 2f2fad08 ("kvm: x86/mmu: Add functions to handle changed TDP SPTEs")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-6-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Bail from fast_page_fault() if the SPTE is not a shadow-present SPTE.
Functionally, this is not strictly necessary as the !is_access_allowed()
check will eventually reject the fast path, but an early check on
shadow-present skips unnecessary checks and will allow a future patch to
tweak the A/D status auditing to warn if KVM attempts to query A/D bits
without first ensuring the SPTE is a shadow-present SPTE.

Note, is_shadow_present_pte() is quite expensive at this time, i.e. this
might be a net negative in the short term.  A future patch will optimize
is_shadow_present_pte() to a single AND operation and remedy the issue.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-4-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add typedefs for the MMU handlers that are invoked when walking the MMU
SPTEs (rmaps in legacy MMU) to act on a host virtual address range.

No functional change intended.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210226010329.1766033-5-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Override the shadow root level in the MMU context when configuring
NPT for shadowing nested NPT.  The level is always tied to the TDP level
of the host, not whatever level the guest happens to be using.

Fixes: 096586fd ("KVM: nSVM: Correctly set the shadow NPT root level in its MMU role")
Cc: stable@vger.kernel.org
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-2-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

WARN if KVM is about to dereference a NULL pae_root or lm_root when
loading an MMU, and convert the BUG() on a bad shadow_root_level into a
WARN (now that errors are handled cleanly).  With nested NPT, botching
the level and sending KVM down the wrong path is all too easy, and the
on-demand allocation of pae_root and lm_root means bugs crash the host.
Obviously, KVM could unconditionally allocate the roots, but that's
arguably a worse failure mode as it would potentially corrupt the guest
instead of crashing it.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-18-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For clarity, explicitly skip syncing roots if the MMU load failed
instead of relying on the !VALID_PAGE check in kvm_mmu_sync_roots().
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-17-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Unexport the MMU load and unload helpers now that they are no longer
used (incorrectly) in vendor code.

Opportunistically move the kvm_mmu_sync_roots() declaration into mmu.h,
it should not be exposed to vendor code.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-16-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Set the C-bit in SPTEs that are set outside of the normal MMU flows,
specifically the PDPDTRs and the handful of special cased "LM root"
entries, all of which are shadow paging only.

Note, the direct-mapped-root PDPTR handling is needed for the scenario
where paging is disabled in the guest, in which case KVM uses a direct
mapped MMU even though TDP is disabled.

Fixes: d0ec49d4 ("kvm/x86/svm: Support Secure Memory Encryption within KVM")
Cc: stable@vger.kernel.org
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-11-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Exempt NULL PAE roots from the check to detect leaks, since
kvm_mmu_free_roots() doesn't set them back to INVALID_PAGE.  Stop hiding
the WARNs to detect PAE root leaks behind MMU_WARN_ON, the hidden WARNs
obviously didn't do their job given the hilarious number of bugs that
could lead to PAE roots being leaked, not to mention the above false
positive.

Opportunistically delete a warning on root_hpa being valid, there's
nothing special about 4/5-level shadow pages that warrants a WARN.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-9-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Check the validity of the PDPTRs before allocating any of the PAE roots,
otherwise a bad PDPTR will cause KVM to leak any previously allocated
roots.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-8-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Hold the mmu_lock for write for the entire duration of allocating and
initializing an MMU's roots.  This ensures there are MMU pages available
and thus prevents root allocations from failing.  That in turn fixes a
bug where KVM would fail to free valid PAE roots if a one of the later
roots failed to allocate.

Add a comment to make_mmu_pages_available() to call out that the limit
is a soft limit, e.g. KVM will temporarily exceed the threshold if a
page fault allocates multiple shadow pages and there was only one page
"available".

Note, KVM _still_ leaks the PAE roots if the guest PDPTR checks fail.
This will be addressed in a future commit.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-7-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the on-demand allocation of the pae_root and lm_root pages, used by
nested NPT for 32-bit L1s, into a separate helper.  This will allow a
future patch to hold mmu_lock while allocating the non-special roots so
that make_mmu_pages_available() can be checked once at the start of root
allocation, and thus avoid having to deal with failure in the middle of
root allocation.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-6-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Allocate lm_root before the PAE roots so that the PAE roots aren't
leaked if the memory allocation for the lm_root happens to fail.

Note, KVM can still leak PAE roots if mmu_check_root() fails on a guest's
PDPTR, or if mmu_alloc_root() fails due to MMU pages not being available.
Those issues will be fixed in future commits.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-5-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Grab 'mmu' and do s/vcpu->arch.mmu/mmu to shorten line lengths and yield
smaller diffs when moving code around in future cleanup without forcing
the new code to use the same ugly pattern.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-4-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>