Re: [PATCH v2] KVM: x86: Check for rmaps allocation

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On 1/7/22 18:01, Sean Christopherson wrote:
On Wed, Jan 05, 2022, Peter Xu wrote:
On Wed, Jan 05, 2022 at 09:33:37AM +0530, Nikunj A Dadhania wrote:
With TDP MMU being the default now, access to mmu_rmaps_stat debugfs
file causes following oops:

BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 7 PID: 3185 Comm: cat Not tainted 5.16.0-rc4+ #204
RIP: 0010:pte_list_count+0x6/0x40
  Call Trace:
   <TASK>
   ? kvm_mmu_rmaps_stat_show+0x15e/0x320
   seq_read_iter+0x126/0x4b0
   ? aa_file_perm+0x124/0x490
   seq_read+0xf5/0x140
   full_proxy_read+0x5c/0x80
   vfs_read+0x9f/0x1a0
   ksys_read+0x67/0xe0
   __x64_sys_read+0x19/0x20
   do_syscall_64+0x3b/0xc0
   entry_SYSCALL_64_after_hwframe+0x44/0xae
  RIP: 0033:0x7fca6fc13912

Return early when rmaps are not present.

Reported-by: Vasant Hegde <vasant.hegde@xxxxxxx>
Tested-by: Vasant Hegde <vasant.hegde@xxxxxxx>
Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---

Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>


Queued, thanks.

Paolo




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