Messages in this thread | | | Date | Mon, 28 Nov 2022 21:00:32 +0800 | From | Baolu Lu <> | Subject | Re: [PATCH v2 4/7] iommu: Let iommu.strict override ops->def_domain_type |
| |
On 2022/11/28 19:10, Niklas Schnelle wrote: > On Thu, 2022-11-17 at 09:55 +0800, Baolu Lu wrote: >> On 2022/11/17 1:16, Niklas Schnelle wrote: >>> When iommu.strict=1 is set or iommu_set_dma_strict() was called we >>> should use IOMMU_DOMAIN_DMA irrespective of ops->def_domain_type. >>> >>> Signed-off-by: Niklas Schnelle<schnelle@linux.ibm.com> >>> --- >>> drivers/iommu/iommu.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >>> index 65a3b3d886dc..d9bf94d198df 100644 >>> --- a/drivers/iommu/iommu.c >>> +++ b/drivers/iommu/iommu.c >>> @@ -1562,6 +1562,9 @@ static int iommu_get_def_domain_type(struct device *dev) >>> { >>> const struct iommu_ops *ops = dev_iommu_ops(dev); >>> >>> + if (iommu_dma_strict) >>> + return IOMMU_DOMAIN_DMA; >> If any quirky device must work in IOMMU identity mapping mode, this >> might introduce functional regression. At least for VT-d platforms, some >> devices do require IOMMU identity mapping mode for functionality. > That's a good point. How about instead of unconditionally returning > IOMMU_DOMAIN_DMA we just do so if the domain type returned by ops- >> def_domain_type uses a flush queue (i.e. the __IOMMU_DOMAIN_DMA_FQ bit > is set). That way a device that only supports identity mapping gets to > set that but iommu_dma_strict at least always prevents use of an IOVA > flush queue.
def_domain_type returns IOMMU_DOMAIN_DMA, IOMMU_DOMAIN_IDENTIRY or 0 (don't care). From a code perspective, you can force IOMMU_DOMAIN_DMA if def_domain_type() returns 0.
*But* you need to document the relationship between strict mode and default domain type somewhere and get that agreed with Robin.
Best regards, baolu
| |