Messages in this thread | | | From | Kai-Heng Feng <> | Subject | [Regression] "iommu/amd: Relax locking in dma_ops path" makes tg3 ethernet transmit queue timeout | Date | Mon, 18 May 2020 17:06:45 +0800 |
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Hi,
Broadcom ethernet tg3 unusable after commit 92d420ec028d ("iommu/amd: Relax locking in dma_ops path"). After a short period it stops: [ 122.717144] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:303 dev_watchdog+0x237/0x240() [ 122.717152] NETDEV WATCHDOG: enp3s0 (tg3): transmit queue 0 timed out
After testing the patch section by section, this is the part that caused the regression:
@@ -2578,19 +2580,8 @@ static dma_addr_t map_page(struct device *dev, struct page *page,
dma_mask = *dev->dma_mask;
- spin_lock_irqsave(&domain->lock, flags); - - addr = __map_single(dev, domain->priv, paddr, size, dir, false, + return __map_single(dev, domain->priv, paddr, size, dir, false, dma_mask); - if (addr == DMA_ERROR_CODE) - goto out; - - domain_flush_complete(domain); - -out: - spin_unlock_irqrestore(&domain->lock, flags); - - return addr; }
Particularly, as soon as the spinlock is removed, the issue can be reproduced. Function domain_flush_complete() doesn't seem to affect the status.
However, the .map_page callback was removed by be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api"), so there's no easy revert for this issue.
This is still reproducible as of today's mainline kernel, v5.7-rc6.
Kai-Heng
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