Right now, ZONE_DEVICE memory is always set PG_reserved. We want to
change that.
KVM has this weird use case that you can map anything from /dev/mem
into the guest. pfn_valid() is not a reliable check whether the memmap
was initialized and can be touched. pfn_to_online_page() makes sure
that we have an initialized memmap. Note that ZONE_DEVICE memory is
never online (IOW, managed by the buddy).
Switching to pfn_to_online_page() keeps the existing behavior for
PFNs without a memmap and for ZONE_DEVICE memory.
Cc: Paul Mackerras <paulus@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_mmu_radix.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 2d415c36a61d..05397c0561fc 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -801,12 +801,14 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
writing, upgrade_p);
if (is_error_noslot_pfn(pfn))
return -EFAULT;
- page = NULL;
- if (pfn_valid(pfn)) {
- page = pfn_to_page(pfn);
- if (PageReserved(page))
- page = NULL;
- }
+ /*
+ * We treat any pages that are not online (not managed by the
+ * buddy) as reserved - this includes ZONE_DEVICE pages and
+ * pages without a memmap (e.g., mapped via /dev/mem).
+ */
+ page = pfn_to_online_page(pfn);
+ if (page && PageReserved(page))
+ page = NULL;
}
/*
--
2.21.0
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