Re: [PATCH v10 7/9] KVM: Update lpage info when private/shared memory are mixed

Sean Christopherson
2023-01-13T23:16:45Z

On Fri, Dec 02, 2022, Chao Peng wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9a07380f8d3c..5aefcff614d2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12362,6 +12362,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
> if ((slot->base_gfn + npages) & (KVM_PAGES_PER_HPAGE(level) - 1))
> linfo[lpages - 1].disallow_lpage = 1;
> ugfn = slot->userspace_addr >> PAGE_SHIFT;
> + if (kvm_slot_can_be_private(slot))
> + ugfn |= slot->restricted_offset >> PAGE_SHIFT;
> /*
> * If the gfn and userspace address are not aligned wrt each
> * other, disable large page support for this slot.

Forgot to talk about the bug. This code needs to handle the scenario where a
memslot is created with existing, non-uniform attributes. It might be a bit ugly
(I didn't even try to write the code), but it's definitely possible, and since
memslot updates are already slow I think it's best to handle things here.

In the meantime, I added this so we don't forget to fix it before merging.

#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
pr_crit_once("FIXME: Walk the memory attributes of the slot and set the mixed status appropriately");
#endif