Messages in this thread | | | Date | Tue, 26 Apr 2022 19:49:20 +0200 | Subject | Re: [PATCH] KVM: x86/mmu: add lockdep check before lookup_address_in_mm() | From | Paolo Bonzini <> |
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On 3/28/22 20:15, Sean Christopherson wrote: >> lookup_address_in_mm() walks the host page table as if it is a >> sequence of_static_ memory chunks. This is clearly dangerous. > Yeah, it's broken. The proper fix is do something like what perf uses, or maybe > just genericize and reuse the code from commit 8af26be06272 > ("perf/core: Fix arch_perf_get_page_size()). >
Indeed, KVM could use perf_get_pgtable_size(). The conversion from the result of *_leaf_size() to level is basically (ctz(size) - 12) / 9.
Alternatively, there are the three difference between perf_get_page_size() and lookup_address_in_pgd():
* the *_offset_lockless() macros, which are unnecessary on x86
* READ_ONCE, which is important but in practice unlikely to make a difference
* local_irq_{save,restore} around the walk
The last is the important one and it should be added to lookup_address_in_pgd().
Paolo
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