From: Sean Christopherson seanjc@google.com
stable inclusion from stable-v6.6.5 commit fcda4d22f5df70fac308d7654bcbeb6fea2d2a47 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 4ea95c04fa6b9043a1a301240996aeebe3cb28ec ]
Drop the vfio_file_iommu_group() stub and instead unconditionally declare the function to fudge around a KVM wart where KVM tries to do symbol_get() on vfio_file_iommu_group() (and other VFIO symbols) even if CONFIG_VFIO=n.
Ensuring the symbol is always declared fixes a PPC build error when modules are also disabled, in which case symbol_get() simply points at the address of the symbol (with some attributes shenanigans). Because KVM does symbol_get() instead of directly depending on VFIO, the lack of a fully defined symbol is not problematic (ugly, but "fine").
arch/powerpc/kvm/../../../virt/kvm/vfio.c:89:7: error: attribute declaration must precede definition [-Werror,-Wignored-attributes] fn = symbol_get(vfio_file_iommu_group); ^ include/linux/module.h:805:60: note: expanded from macro 'symbol_get' #define symbol_get(x) ({ extern typeof(x) x __attribute__((weak,visibility("hidden"))); &(x); }) ^ include/linux/vfio.h:294:35: note: previous definition is here static inline struct iommu_group *vfio_file_iommu_group(struct file *file) ^ arch/powerpc/kvm/../../../virt/kvm/vfio.c:89:7: error: attribute declaration must precede definition [-Werror,-Wignored-attributes] fn = symbol_get(vfio_file_iommu_group); ^ include/linux/module.h:805:65: note: expanded from macro 'symbol_get' #define symbol_get(x) ({ extern typeof(x) x __attribute__((weak,visibility("hidden"))); &(x); }) ^ include/linux/vfio.h:294:35: note: previous definition is here static inline struct iommu_group *vfio_file_iommu_group(struct file *file) ^ 2 errors generated.
Although KVM is firmly in the wrong (there is zero reason for KVM to build virt/kvm/vfio.c when VFIO is disabled), fudge around the error in VFIO as the stub is unnecessary and doesn't serve its intended purpose (KVM is the only external user of vfio_file_iommu_group()), and there is an in-flight series to clean up the entire KVM<->VFIO interaction, i.e. fixing this in KVM would result in more churn in the long run, and the stub needs to go away regardless.
Reported-by: kernel test robot lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202308251949.5IiaV0sz-lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202309030741.82aLACDG-lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202309110914.QLH0LU6L-lkp@intel.com Link: https://lore.kernel.org/all/0-v1-08396538817d+13c5-vfio_kvm_kconfig_jgg@nvid... Link: https://lore.kernel.org/all/20230916003118.2540661-1-seanjc@google.com Cc: Nick Desaulniers ndesaulniers@google.com Cc: Jason Gunthorpe jgg@nvidia.com Tested-by: Michael Ellerman mpe@ellerman.id.au Fixes: c1cce6d079b8 ("vfio: Compile vfio_group infrastructure optionally") Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Link: https://lore.kernel.org/r/20231130001000.543240-1-seanjc@google.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- include/linux/vfio.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/include/linux/vfio.h b/include/linux/vfio.h index 454e9295970c..a65b2513f8cd 100644 --- a/include/linux/vfio.h +++ b/include/linux/vfio.h @@ -289,16 +289,12 @@ void vfio_combine_iova_ranges(struct rb_root_cached *root, u32 cur_nodes, /* * External user API */ -#if IS_ENABLED(CONFIG_VFIO_GROUP) struct iommu_group *vfio_file_iommu_group(struct file *file); + +#if IS_ENABLED(CONFIG_VFIO_GROUP) bool vfio_file_is_group(struct file *file); bool vfio_file_has_dev(struct file *file, struct vfio_device *device); #else -static inline struct iommu_group *vfio_file_iommu_group(struct file *file) -{ - return NULL; -} - static inline bool vfio_file_is_group(struct file *file) { return false;