This is a note to let you know that I've just added the patch titled
vfio: Drop vfio_file_iommu_group() stub to fudge around a KVM wart
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vfio-drop-vfio_file_iommu_group-stub-to-fudge-around.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 527552028ebca1cba0848b40b71ff6c9346ff6a8
Author: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Wed Nov 29 16:10:00 2023 -0800
vfio: Drop vfio_file_iommu_group() stub to fudge around a KVM wart
[ 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@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202308251949.5IiaV0sz-lkp@xxxxxxxxx
Closes: https://lore.kernel.org/oe-kbuild-all/202309030741.82aLACDG-lkp@xxxxxxxxx
Closes: https://lore.kernel.org/oe-kbuild-all/202309110914.QLH0LU6L-lkp@xxxxxxxxx
Link: https://lore.kernel.org/all/0-v1-08396538817d+13c5-vfio_kvm_kconfig_jgg@xxxxxxxxxx
Link: https://lore.kernel.org/all/20230916003118.2540661-1-seanjc@xxxxxxxxxx
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Fixes: c1cce6d079b8 ("vfio: Compile vfio_group infrastructure optionally")
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231130001000.543240-1-seanjc@xxxxxxxxxx
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 454e9295970c4..a65b2513f8cdc 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;
