6.15-stable review patch. If anyone has any objections, please let me know.
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From: Robin Murphy robin.murphy@arm.com
commit 0c8e9c148e29a983e67060fb4944a8ca79d4362a upstream.
Although the lock-juggling is only a temporary workaround, we don't want it to make things avoidably worse. Jason was right to be nervous, since bus_iommu_probe() doesn't care *which* IOMMU instance it's probing for, so it probably is possible for one walk to finish a probe which a different walk started, thus we do want to check for that.
Also there's no need to drop the lock just to have of_iommu_configure() do nothing when a fwspec already exists; check that directly and avoid opening a window at all in that (still somewhat likely) case.
Suggested-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Robin Murphy robin.murphy@arm.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Link: https://lore.kernel.org/r/09d901ad11b3a410fbb6e27f7d04ad4609c3fe4a.174170636... Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/iommu.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -422,13 +422,15 @@ static int iommu_init_device(struct devi * is buried in the bus dma_configure path. Properly unpicking that is * still a big job, so for now just invoke the whole thing. The device * already having a driver bound means dma_configure has already run and - * either found no IOMMU to wait for, or we're in its replay call right - * now, so either way there's no point calling it again. + * found no IOMMU to wait for, so there's no point calling it again. */ - if (!dev->driver && dev->bus->dma_configure) { + if (!dev->iommu->fwspec && !dev->driver && dev->bus->dma_configure) { mutex_unlock(&iommu_probe_device_lock); dev->bus->dma_configure(dev); mutex_lock(&iommu_probe_device_lock); + /* If another instance finished the job for us, skip it */ + if (!dev->iommu || dev->iommu_group) + return -ENODEV; } /* * At this point, relevant devices either now have a fwspec which will