Adding Robin, Yu and swiotlb list. Hi Greg, There is an on-going discussion whether to revert this patch, because it breaks a corner case in MIPS when many kernel CONFIGs are not enabled (related to PCI and device). As a result, MIPS pre-allocates only PAGE_SIZE buffer as swiotlb. https://lore.kernel.org/all/20220820012031.1285979-1-yuzhao@xxxxxxxxxx/ However, the core idea of the patch is to panic on purpose if the swiotlb is configured with <1MB memory, in order to sync with the remap failure handler in swiotlb_init_remap(). Therefore, I am waiting for suggestion from Christoph whether (1) to revert this patch, or (2) enforce the restriction to disallow <1MB allocation. Thank you very much! Dongli Zhang On 8/23/22 1:03 AM, Greg Kroah-Hartman wrote: > From: Dongli Zhang <dongli.zhang@xxxxxxxxxx> > > [ Upstream commit 0bf28fc40d89b1a3e00d1b79473bad4e9ca20ad1 ] > > Panic on purpose if nslabs is too small, in order to sync with the remap > retry logic. > > In addition, print the number of bytes for tlb alloc failure. > > Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx> > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > kernel/dma/swiotlb.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 5830dce6081b..f5304e2f6a35 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -242,6 +242,9 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, > if (swiotlb_force_disable) > return; > > + if (nslabs < IO_TLB_MIN_SLABS) > + panic("%s: nslabs = %lu too small\n", __func__, nslabs); > + > /* > * By default allocate the bounce buffer memory from low memory, but > * allow to pick a location everywhere for hypervisors with guest > @@ -254,7 +257,8 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, > else > tlb = memblock_alloc_low(bytes, PAGE_SIZE); > if (!tlb) { > - pr_warn("%s: failed to allocate tlb structure\n", __func__); > + pr_warn("%s: Failed to allocate %zu bytes tlb structure\n", > + __func__, bytes); > return; > } > >
