[PATCH v2 02/14] powerpc/pseries/iommu: Makes sure IOMMU_PAGE_SIZE <= PAGE_SIZE
From: Leonardo Bras <hidden>
Date: 2020-09-11 17:19:02
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Having System pagesize < IOMMU pagesize may cause a page owned by another process/VM to be written by a buggy driver / device. As it's intended to use DDW for indirect mapping, it's possible to get a configuration where (PAGE_SIZE = 4k) < (IOMMU_PAGE_SIZE() = 64k). To avoid this, make sure create_ddw() can only use pagesize <= PAGE_SIZE. Signed-off-by: Leonardo Bras <redacted> --- arch/powerpc/platforms/pseries/iommu.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 9db3927607a4..4eff3a6a441e 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c@@ -1206,17 +1206,20 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) goto out_failed; } } - if (query.page_size & 4) { - page_shift = 24; /* 16MB */ - } else if (query.page_size & 2) { + + /* Choose the biggest pagesize available <= PAGE_SHIFT */ + if ((query.page_size & 4)) { + page_shift = 24; /* 16MB - Hugepages */ + } else if ((query.page_size & 2) && PAGE_SHIFT >= 16) { page_shift = 16; /* 64kB */ - } else if (query.page_size & 1) { + } else if ((query.page_size & 1) && PAGE_SHIFT >= 12) { page_shift = 12; /* 4kB */ } else { dev_dbg(&dev->dev, "no supported direct page size in mask %x", query.page_size); goto out_failed; } + /* verify the window * number of ptes will map the partition */ /* check largest block * page size > max memory hotplug addr */ max_addr = ddw_memory_hotplug_max();
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2.25.4