Re: [PATCH kernel] powerpc/powernv: Fix iommu table size calculation hook for small tables
From: Alexey Kardashevskiy <hidden>
Date: 2017-04-28 06:20:06
On Thu, 13 Apr 2017 17:05:27 +1000 Alexey Kardashevskiy [off-list ref] wrote:
When the userspace requests a small TCE table (which takes less than the system page size) and more than 1 TCE level, the existing code returns a single page size which is a bug as each additional TCE level requires at least one page and this is what pnv_pci_ioda2_table_alloc_pages() does. And we end up seeing WARN_ON(!ret && ((*ptbl)->it_allocated_size != table_size)) in drivers/vfio/vfio_iommu_spapr_tce.c. This replaces incorrect _ALIGN_UP() (which aligns zero up to zero) with max_t() to fix the bug. Besides removing WARN_ON(), there should be no other changes in behaviour.
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Signed-off-by: Alexey Kardashevskiy <redacted> --- arch/powerpc/platforms/powernv/pci-ioda.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c index 6d0da5dfc955..a0d046adcf45 100644 --- a/arch/powerpc/platforms/powernv/pci-ioda.c +++ b/arch/powerpc/platforms/powernv/pci-ioda.c@@ -2538,7 +2538,8 @@ static unsigned long pnv_pci_ioda2_get_table_size(__u32 page_shift, tce_table_size /= direct_table_size; tce_table_size <<= 3; - tce_table_size = _ALIGN_UP(tce_table_size, direct_table_size); + tce_table_size = max_t(unsigned long, + tce_table_size, direct_table_size); } return bytes;
-- Alexey