KVM: Don't WARN if kvm_pfn_to_page() encounters a "reserved" pfn

Drop a WARN_ON() if kvm_pfn_to_page() encounters a "reserved" pfn, which
in this context means a struct page that has PG_reserved but is not a/the
ZERO_PAGE and is not a ZONE_DEVICE page.  The usage, via gfn_to_page(),
in x86 is safe as gfn_to_page() is used only to retrieve a page from
KVM-controlled memslot, but the usage in PPC and s390 operates on
arbitrary gfns and thus memslots that can be backed by incompatible
memory.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220429010416.2788472-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4732a99..78d280e 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2725,10 +2725,8 @@ static struct page *kvm_pfn_to_page(kvm_pfn_t pfn)
        if (is_error_noslot_pfn(pfn))
                return KVM_ERR_PTR_BAD_PAGE;
 
-       if (kvm_is_reserved_pfn(pfn)) {
-               WARN_ON(1);
+       if (kvm_is_reserved_pfn(pfn))
                return KVM_ERR_PTR_BAD_PAGE;
-       }
 
        return pfn_to_page(pfn);
 }