When we call rmap_remove(), we (almost) always immediately follow it by
an __set_spte() to a nonpresent pte.  Since we need to perform the two
operations atomically, to avoid losing the dirty and accessed bits, introduce
a helper drop_spte() and convert all call sites.

The operation is still nonatomic at this point.
Signed-off-by: NAvi Kivity <avi@redhat.com>

Commit 341d9b535b6c simplify reload logic while entry guest mode, it
can avoid unnecessary sync-root if KVM_REQ_MMU_RELOAD and
KVM_REQ_MMU_SYNC both set.

But, it cause a issue that when we handle 'KVM_REQ_TLB_FLUSH', the
root is invalid, it is triggered during my test:

Kernel BUG at ffffffffa00212b8 [verbose debug info unavailable]
......

Fixed by directly return if the root is not ready.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This patch converts unnecessary divide and modulo operations
in the KVM large page related code into logical operations.
This allows to convert gfn_t to u64 while not breaking 32
bit builds.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

While we sync many unsync sp at one time(in mmu_sync_children()),
we may mapping the spte writable, it's dangerous, if one unsync
sp's mapping gfn is another unsync page's gfn.

For example:

SP1.pte[0] = P
SP2.gfn's pfn = P
[SP1.pte[0] = SP2.gfn's pfn]

First, we write protected SP1 and SP2, but SP1 and SP2 are still the
unsync sp.

Then, sync SP1 first, it will detect SP1.pte[0].gfn only has one unsync-sp,
that is SP2, so it will mapping it writable, but we plan to sync SP2 soon,
at this point, the SP2->unsync is not reliable since later we sync SP2 but
SP2->gfn is already writable.

So the final result is: SP2 is the sync page but SP2.gfn is writable.

This bug will corrupt guest's page table, fixed by mark read-only mapping
if the mapped gfn has shadow pages.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Makes it a little more readable and hackable.
Signed-off-by: NAvi Kivity <avi@redhat.com>

As advertised in feature-removal-schedule.txt.  Equivalent support is provided
by overlapping memory regions.
Signed-off-by: NAvi Kivity <avi@redhat.com>

While we mark the parent's unsync_child_bitmap, if the parent is already
unsynced, it no need walk it's parent, it can reduce some unnecessary
workload
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

In current code, some page's unsync_child_bitmap is not cleared completely
in mmu_sync_children(), for example, if two PDPEs shard one PDT, one of
PDPE's unsync_child_bitmap is not cleared.

Currently, it not harm anything just little overload, but it's the prepare
work for the later patch
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Decrease sp->unsync_children after clear unsync_child_bitmap bit
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

If the sync-sp just sync transient, don't mark its pte notrap
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

The sync page is already write protected in mmu_sync_children(), don't
write protected it again
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

On Intel, we call skip_emulated_instruction() even if we injected a #GP,
resulting in the #GP pointing at the wrong address.

Fix by injecting the exception and skipping the instruction at the same place,
so we can do just one or the other.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

delay local tlb flush until enter guest moden, it can reduce vpid flush
frequency and reduce remote tlb flush IPI(if KVM_REQ_TLB_FLUSH bit is
already set, IPI is not sent)
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Use kvm_mmu_flush_tlb() function instead of calling
kvm_x86_ops->tlb_flush(vcpu) directly.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

This remote tlb flush is no necessary since we have synced while
sp is zapped
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

collect remote tlb flush in kvm_mmu_pte_write() path
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Now, we can safely to traverse sp hlish
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Using kvm_mmu_prepare_zap_page() and kvm_mmu_zap_page() instead of
kvm_mmu_zap_page() that can reduce remote tlb flush IPI
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In the later patch, we will modify sp's zapping way like below:

	kvm_mmu_prepare_zap_page A
	kvm_mmu_prepare_zap_page B
	kvm_mmu_prepare_zap_page C
	....
	kvm_mmu_commit_zap_page

[ zaped multiple sps only need to call kvm_mmu_commit_zap_page once ]

In __kvm_mmu_free_some_pages() function, the free page number is
getted form 'vcpu->kvm->arch.n_free_mmu_pages' in loop, it will
hinders us to apply kvm_mmu_prepare_zap_page() and kvm_mmu_commit_zap_page()
since kvm_mmu_prepare_zap_page() not free sp.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Using kvm_mmu_prepare_zap_page() and kvm_mmu_commit_zap_page() to
split kvm_mmu_zap_page() function, then we can:

- traverse hlist safely
- easily to gather remote tlb flush which occurs during page zapped

Those feature can be used in the later patches
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Introduce for_each_gfn_sp() and for_each_gfn_indirect_valid_sp() to
cleanup hlist traverseing
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In kvm_mmu_unprotect_page(), the invalid sp can be skipped
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

There's no need to calculate quadrant if tdp is enabled.
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

When tdp is enabled, the guest's cr0.wp shouldn't have any effect on spte
permissions.
Signed-off-by: NAvi Kivity <avi@redhat.com>

Since we have is_writable_pte(), make use of it.
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In Document/kvm/mmu.txt:
  gfn:
    Either the guest page table containing the translations shadowed by this
    page, or the base page frame for linear translations. See role.direct.

But in __direct_map(), the base gfn calculation is incorrect,
it does not calculate correctly when level=3 or 4.

Fix by using PT64_LVL_ADDR_MASK() which accounts for all levels correctly.
Reported-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

When sp->role.direct is set, sp->gfns does not contain any essential
information, leaf sptes reachable from this sp are for a continuous
guest physical memory range (a linear range).
So sp->gfns[i] (if it was set) equals to sp->gfn + i. (PT_PAGE_TABLE_LEVEL)
Obviously, it is not essential information, we can calculate it when need.

It means we don't need sp->gfns when sp->role.direct=1,
Thus we can save one page usage for every kvm_mmu_page.

Note:
  Access to sp->gfns must be wrapped by kvm_mmu_page_get_gfn()
  or kvm_mmu_page_set_gfn().
  It is only exposed in FNAME(sync_page).
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Allow more page become asynchronous at getting sp time, if need create new
shadow page for gfn but it not allow unsync(level > 1), we should unsync all
gfn's unsync page
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In current code, shadow page can become asynchronous only if one
shadow page for a gfn, this rule is too strict, in fact, we can
let all last mapping page(i.e, it's the pte page) become unsync,
and sync them at invlpg or flush tlb time.

This patch allow more page become asynchronous at gfn mapping time
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Signed-off-by: NAvi Kivity <avi@redhat.com>

Two cases maybe happen in kvm_mmu_get_page() function:

- one case is, the goal sp is already in cache, if the sp is unsync,
  we only need update it to assure this mapping is valid, but not
  mark it sync and not write-protect sp->gfn since it not broke unsync
  rule(one shadow page for a gfn)

- another case is, the goal sp not existed, we need create a new sp
  for gfn, i.e, gfn (may)has another shadow page, to keep unsync rule,
  we should sync(mark sync and write-protect) gfn's unsync shadow page.
  After enabling multiple unsync shadows, we sync those shadow pages
  only when the new sp not allow to become unsync(also for the unsyc
  rule, the new rule is: allow all pte page become unsync)
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Split kvm_sync_page() into kvm_sync_page() and kvm_sync_page_transient()
to clarify the code address Avi's suggestion

kvm_sync_page_transient() function only update shadow page but not mark
it sync and not write protect sp->gfn. it will be used by later patch
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

Remove rmap before clear spte otherwise it will trigger BUG_ON() in
some functions such as rmap_write_protect().
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Use kmem_cache_free to free objects allocated by kmem_cache_alloc.
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

mmu.free() already set root_hpa to INVALID_PAGE, no need to do it again in the
destory_kvm_mmu().

kvm_x86_ops->set_cr4() and set_efer() already assign cr4/efer to
vcpu->arch.cr4/efer, no need to do it again later.
Signed-off-by: NSheng Yang <sheng@linux.intel.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

We drop the mmu lock between freeing memory and allocating the roots; this
allows some other vcpu to sneak in and allocate memory.

While the race is benign (resulting only in temporary overallocation, not oom)
it is simple and easy to fix by moving the freeing close to the allocation.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Do not kill VM when instruction emulation fails. Inject #UD and report
failure to userspace instead. Userspace may choose to reenter guest if
vcpu is in userspace (cpl == 3) in which case guest OS will kill
offending process and continue running.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Currently, kvm_mmu_zap_page() returning the number of freed children sp.
This might confuse the caller, because caller don't know the actual freed
number. Let's make kvm_mmu_zap_page() return the number of pages it actually
freed.
Signed-off-by: NGui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

In common cases, guest SRAO MCE will cause corresponding poisoned page
be un-mapped and SIGBUS be sent to QEMU-KVM, then QEMU-KVM will relay
the MCE to guest OS.

But it is reported that if the poisoned page is accessed in guest
after unmapping and before MCE is relayed to guest OS, userspace will
be killed.

The reason is as follows. Because poisoned page has been un-mapped,
guest access will cause guest exit and kvm_mmu_page_fault will be
called. kvm_mmu_page_fault can not get the poisoned page for fault
address, so kernel and user space MMIO processing is tried in turn. In
user MMIO processing, poisoned page is accessed again, then userspace
is killed by force_sig_info.

To fix the bug, kvm_mmu_page_fault send HWPOISON signal to QEMU-KVM
and do not try kernel and user space MMIO processing for poisoned
page.

[xiao: fix warning introduced by avi]
Reported-by: NMax Asbock <masbock@linux.vnet.ibm.com>
Signed-off-by: NHuang Ying <ying.huang@intel.com>
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>