From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Fri, 28 Sep 2018 13:51:31 +0100 Subject: [PATCH v8 3/7] iommu: Add "iommu.strict" command line option In-Reply-To: <799fad801970298385af3abc8ca82620ad62c000.1537458163.git.robin.murphy@arm.com> References: <799fad801970298385af3abc8ca82620ad62c000.1537458163.git.robin.murphy@arm.com> Message-ID: <20180928125130.GD1577@brain-police> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Sep 20, 2018 at 05:10:23PM +0100, Robin Murphy wrote: > From: Zhen Lei > > Add a generic command line option to enable lazy unmapping via IOVA > flush queues, which will initally be suuported by iommu-dma. This echoes > the semantics of "intel_iommu=strict" (albeit with the opposite default > value), but in the driver-agnostic fashion of "iommu.passthrough". > > Signed-off-by: Zhen Lei > [rm: move handling out of SMMUv3 driver, clean up documentation] > Signed-off-by: Robin Murphy > --- > > v8: > - Rename "non-strict" to "strict" to better match existing options > - Rewrite doc text/commit message > - Downgrade boot-time message from warn/taint to info > > .../admin-guide/kernel-parameters.txt | 12 ++++++++++ > drivers/iommu/iommu.c | 23 +++++++++++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 9871e649ffef..92ae12aeabf4 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1749,6 +1749,18 @@ > nobypass [PPC/POWERNV] > Disable IOMMU bypass, using IOMMU for PCI devices. > > + iommu.strict= [ARM64] Configure TLB invalidation behaviour > + Format: { "0" | "1" } > + 0 - Lazy mode. > + Request that DMA unmap operations use deferred > + invalidation of hardware TLBs, for increased > + throughput at the cost of reduced device isolation. > + Will fall back to strict mode if not supported by > + the relevant IOMMU driver. > + 1 - Strict mode (default). > + DMA unmap operations invalidate IOMMU hardware TLBs > + synchronously. > + > iommu.passthrough= > [ARM64] Configure DMA to bypass the IOMMU by default. > Format: { "0" | "1" } > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 8c15c5980299..02b6603f0616 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -41,6 +41,7 @@ static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY; > #else > static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA; > #endif > +static bool iommu_dma_strict __read_mostly = true; > > struct iommu_callback_data { > const struct iommu_ops *ops; > @@ -131,6 +132,21 @@ static int __init iommu_set_def_domain_type(char *str) > } > early_param("iommu.passthrough", iommu_set_def_domain_type); > > +static int __init iommu_dma_setup(char *str) > +{ > + int ret; > + > + ret = kstrtobool(str, &iommu_dma_strict); > + if (ret) > + return ret; > + > + if (!iommu_dma_strict) > + pr_info("Enabling deferred TLB invalidation for DMA; protection against malicious/malfunctioning devices may be reduced.\n"); Printing here isn't quite right, because if somebody boots with something like: "iommu.strict=1 iommu.strict=0 iommu.strict=0 iommu.strict=1" then we'll print the wrong thing twice :) I think we either need to drop the print, or move it to a the DMA domain initialisation. Will