On Mon, Jun 03, 2019 at 09:16:17AM +0800, Lu Baolu wrote: > This adds a helper to check whether a device needs to > use bounce buffer. It also provides a boot time option > to disable the bounce buffer. Users can use this to > prevent the iommu driver from using the bounce buffer > for performance gain. > > Cc: Ashok Raj <ashok....@intel.com> > Cc: Jacob Pan <jacob.jun....@linux.intel.com> > Cc: Kevin Tian <kevin.t...@intel.com> > Signed-off-by: Lu Baolu <baolu...@linux.intel.com> > Tested-by: Xu Pengfei <pengfei...@intel.com> > Tested-by: Mika Westerberg <mika.westerb...@intel.com> > --- > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > drivers/iommu/intel-iommu.c | 6 ++++++ > 2 files changed, 11 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index 138f6664b2e2..65685c6e53e4 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1728,6 +1728,11 @@ > Note that using this option lowers the security > provided by tboot because it makes the system > vulnerable to DMA attacks. > + nobounce [Default off] > + Do not use the bounce buffer for untrusted devices like > + the Thunderbolt devices. This will treat the untrusted
My brain has sometimes a hard time parsing 'Not' and 'un'. Could this be: Disable bounce buffer for unstrusted devices ..? And perhaps call it 'noswiotlb' ? Not everyone knows that SWIOTLB = bounce buffer. > + devices as the trusted ones, hence might expose security > + risks of DMA attacks. > > intel_idle.max_cstate= [KNL,HW,ACPI,X86] > 0 disables intel_idle and fall back on acpi_idle. > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 235837c50719..41439647f75d 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -371,6 +371,7 @@ static int dmar_forcedac; > static int intel_iommu_strict; > static int intel_iommu_superpage = 1; > static int iommu_identity_mapping; > +static int intel_no_bounce; intel_swiotlb_on = 1 ? > > #define IDENTMAP_ALL 1 > #define IDENTMAP_GFX 2 > @@ -384,6 +385,8 @@ EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped); > static DEFINE_SPINLOCK(device_domain_lock); > static LIST_HEAD(device_domain_list); > > +#define device_needs_bounce(d) (!intel_no_bounce && dev_is_untrusted(d)) > + > /* > * Iterate over elements in device_domain_list and call the specified > * callback @fn against each element. > @@ -466,6 +469,9 @@ static int __init intel_iommu_setup(char *str) > printk(KERN_INFO > "Intel-IOMMU: not forcing on after tboot. This > could expose security risk for tboot\n"); > intel_iommu_tboot_noforce = 1; > + } else if (!strncmp(str, "nobounce", 8)) { > + pr_info("Intel-IOMMU: No bounce buffer. This could > expose security risks of DMA attacks\n"); Again, Intel-IOMMU: No SWIOTLB. T.. blah blah' Asking for this as doing 'dmesg | grep SWIOTLB' will expose nicely all the SWIOTLB invocations.. > + intel_no_bounce = 1; > } > > str += strcspn(str, ","); > -- > 2.17.1 > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu