In some architectures, KVM could be defined as a module. If there is a pending folio_put() while KVM is unloaded, the system could crash. By having a helper check for that and call the function only if it's available, we are able to handle that case more gracefully. Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx> --- This patch could be squashed with the previous one of the maintainers think it would be better. --- include/linux/kvm_host.h | 5 +---- mm/swap.c | 20 +++++++++++++++++++- virt/kvm/guest_memfd.c | 8 ++++++++ 3 files changed, 28 insertions(+), 5 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 7788e3625f6d..3ad0719bfc4f 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2572,10 +2572,7 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, #endif #ifdef CONFIG_KVM_GMEM_SHARED_MEM -static inline void kvm_gmem_handle_folio_put(struct folio *folio) -{ - WARN_ONCE(1, "A placeholder that shouldn't trigger. Work in progress."); -} +void kvm_gmem_handle_folio_put(struct folio *folio); #endif #endif diff --git a/mm/swap.c b/mm/swap.c index 241880a46358..27dfd75536c8 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -98,6 +98,24 @@ static void page_cache_release(struct folio *folio) unlock_page_lruvec_irqrestore(lruvec, flags); } +#ifdef CONFIG_KVM_GMEM_SHARED_MEM +static void gmem_folio_put(struct folio *folio) +{ +#if IS_MODULE(CONFIG_KVM) + void (*fn)(struct folio *folio); + + fn = symbol_get(kvm_gmem_handle_folio_put); + if (WARN_ON_ONCE(!fn)) + return; + + fn(folio); + symbol_put(kvm_gmem_handle_folio_put); +#else + kvm_gmem_handle_folio_put(folio); +#endif +} +#endif + static void free_typed_folio(struct folio *folio) { switch (folio_get_type(folio)) { @@ -108,7 +126,7 @@ static void free_typed_folio(struct folio *folio) #endif #ifdef CONFIG_KVM_GMEM_SHARED_MEM case PGTY_guestmem: - kvm_gmem_handle_folio_put(folio); + gmem_folio_put(folio); return; #endif default: diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index b2aa6bf24d3a..5fc414becae5 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -13,6 +13,14 @@ struct kvm_gmem { struct list_head entry; }; +#ifdef CONFIG_KVM_GMEM_SHARED_MEM +void kvm_gmem_handle_folio_put(struct folio *folio) +{ + WARN_ONCE(1, "A placeholder that shouldn't trigger. Work in progress."); +} +EXPORT_SYMBOL_GPL(kvm_gmem_handle_folio_put); +#endif /* CONFIG_KVM_GMEM_SHARED_MEM */ + /** * folio_file_pfn - like folio_file_page, but return a pfn. * @folio: The folio which contains this index. -- 2.49.0.rc0.332.g42c0ae87b1-goog