Messages in this thread | | | Date | Fri, 5 Mar 2021 10:22:14 -0800 | From | Sean Christopherson <> | Subject | Re: [PATCH v2 09/17] KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE root |
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On Fri, Mar 05, 2021, Paolo Bonzini wrote: > On 05/03/21 02:10, Sean Christopherson wrote: > > 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... > > I don't dispute this is a good idea, but it deserves one or more comments.
Agreed. What about adding macros?
/* Comment goes here. */ #define INVALID_PAE_ROOT 0 #define IS_VALID_PAE_ROOT(x) (!!(x))
Also, I missed this pattern in mmu_audit.c's mmu_spte_walk():
for (i = 0; i < 4; ++i) { hpa_t root = vcpu->arch.mmu->pae_root[i];
if (root && VALID_PAGE(root)) { root &= PT64_BASE_ADDR_MASK; sp = to_shadow_page(root); __mmu_spte_walk(vcpu, sp, fn, 2); } }
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