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9830209b4a
guest_memfd only supports PAGE_SIZE pages, and khugepaged or MADV_COLLAPSE collapsing pages may result in private memory regions being mapped into host page tables. Add test to verify that MADV_COLLAPSE fails on guest_memfd folios, and any subsequent usage of guest_memfd memory faults in PAGE_SIZE folios. Running this test should not result in any memory failure logs or kernel WARNings. This selftest was added as a result of a syzbot-reported issue where khugepaged operating on guest_memfd memory with MADV_HUGEPAGE caused the collapse of folios, which then subsequently resulted in a WARNing. Link: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44 Suggested-by: David Hildenbrand <david@kernel.org> Signed-off-by: Ackerley Tng <ackerleytng@google.com> Link: https://patch.msgid.link/8048d04f150326d1e2231318aa9f1b3fce3e2e2c.1771630983.git.ackerleytng@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>