Messages in this thread | | | Date | Tue, 5 Oct 2021 19:27:31 +0200 | Subject | Re: [PATCH][next] KVM: x86: Fix allocation sizeof argument | From | Paolo Bonzini <> |
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On 05/10/21 17:41, Sean Christopherson wrote: >> if (*gfn_track == NULL) { >> mutex_unlock(&kvm->slots_arch_lock); > Hrm, this fails to free the gfn_track allocations for previous memslots. The > on-demand rmaps code has the exact same bug (it frees rmaps for previous lpages > in the_current_ slot, but does not free previous slots).
That's not a huge deal because the syscall is failing. So as long as it's not leaked forever, it's okay. The problem is the WARN_ON(slot->arch.rmap[i]), or the missing check in kvm_page_track_enable_mmu_write_tracking, but that's easily fixed. I'd even remove the call to memslot_rmaps_free.
> And having two separate flows (and flags) for rmaps vs. gfn_track is pointless, > and means we have to maintain two near-identical copies of non-obvious code.
I was thinking the separate flow (not so much the flag) is needed because, if KVMGT is enabled, gfn_track is allocated unconditionally. rmaps are added on top of that if shadow paging is enabled; but kvm_page_track_create_memslot will have already created the counter, including the one for KVM_PAGE_TRACK_WRITE.
But looking at the code again, I guess you could call kvm_page_track_enable_mmu_write_tracking inside alloc_all_memslots_rmaps (with a little bit of renaming), and with that the flag would go away.
I'll take a look tomorrow, but I'd rather avoid reverting the patch.
Thanks,
Paolo
> Paolo, is it too late to just drop the original deae4a10f166 ("KVM: x86: only > allocate gfn_track when necessary")? >
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