| Message ID | 41f81c46348db4acd9a542184f10e7ca24f6c219.1536935328.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | Add non-strict mode support for iommu-dma | expand |
On Fri, Sep 14, 2018 at 03:30:22PM +0100, Robin Murphy wrote: > From: Zhen Lei <thunder.leizhen@huawei.com> > > Add a bootup option to make the system manager can choose which mode to > be used. The default mode is strict. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > [rm: move handling out of SMMUv3 driver] > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > .../admin-guide/kernel-parameters.txt | 13 ++++++++++ > drivers/iommu/iommu.c | 26 +++++++++++++++++++ > 2 files changed, 39 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 9871e649ffef..406b91759b62 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1749,6 +1749,19 @@ > nobypass [PPC/POWERNV] > Disable IOMMU bypass, using IOMMU for PCI devices. > > + iommu.non_strict= [ARM64] > + Format: { "0" | "1" } > + 0 - strict mode, default. > + Release IOVAs after the related TLBs are invalid > + completely. > + 1 - non-strict mode. > + Put off TLBs invalidation and release memory first. > + It's good for scatter-gather performance but lacks > + full isolation, an untrusted device can access the > + reused memory because the TLBs may still valid. > + Please take full consideration before choosing this > + mode. Note that, VFIO will always use strict mode. This text needs help. How about something like: 0 - strict mode, default. Invalidate the TLB of the IOMMU hardware as part of every unmap() operation. 1 - lazy mode. Defer TLB invalidation so that the TLB of the IOMMU hardware is invalidated periodically, rather than as part of every unmap() operation. (generally, I think I'd s/non strict/lazy/ in this patch to avoid the double negatives) > + > 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..2cabd0c0a4f3 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_non_strict __read_mostly; > > struct iommu_callback_data { > const struct iommu_ops *ops; > @@ -131,6 +132,24 @@ 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_non_strict); > + if (ret) > + return ret; > + > + if (iommu_dma_non_strict) { > + pr_warn("WARNING: iommu non-strict mode is chosen.\n" > + "It's good for scatter-gather performance but lacks full isolation\n"); Hmm, not sure about this message either and tainting is probably over the top. Maybe drop the taint and just pr_info something like "IOMMU DMA ops using lazy TLB invalidation: unable to protect against malicious devices" > + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); > + } > + > + return 0; > +} > +early_param("iommu.non_strict", iommu_dma_setup); > + > static ssize_t iommu_group_attr_show(struct kobject *kobj, > struct attribute *__attr, char *buf) > { > @@ -1072,6 +1091,13 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev) > group->default_domain = dom; > if (!group->domain) > group->domain = dom; > + > + if (dom && iommu_dma_non_strict) { > + int attr = 1; > + iommu_domain_set_attr(dom, > + DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, > + &attr); > + } Hmm, I don't think we can guarantee that we're working with the DMA domain here. Does this all fall out in the wash for the identity domain? Will
On 2018-09-18 6:10 PM, Will Deacon wrote: > On Fri, Sep 14, 2018 at 03:30:22PM +0100, Robin Murphy wrote: >> From: Zhen Lei <thunder.leizhen@huawei.com> >> >> Add a bootup option to make the system manager can choose which mode to >> be used. The default mode is strict. >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> [rm: move handling out of SMMUv3 driver] >> Signed-off-by: Robin Murphy <robin.murphy@arm.com> >> --- >> .../admin-guide/kernel-parameters.txt | 13 ++++++++++ >> drivers/iommu/iommu.c | 26 +++++++++++++++++++ >> 2 files changed, 39 insertions(+) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index 9871e649ffef..406b91759b62 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -1749,6 +1749,19 @@ >> nobypass [PPC/POWERNV] >> Disable IOMMU bypass, using IOMMU for PCI devices. >> >> + iommu.non_strict= [ARM64] >> + Format: { "0" | "1" } >> + 0 - strict mode, default. >> + Release IOVAs after the related TLBs are invalid >> + completely. >> + 1 - non-strict mode. >> + Put off TLBs invalidation and release memory first. >> + It's good for scatter-gather performance but lacks >> + full isolation, an untrusted device can access the >> + reused memory because the TLBs may still valid. >> + Please take full consideration before choosing this >> + mode. Note that, VFIO will always use strict mode. > > This text needs help. How about something like: > > 0 - strict mode, default. > Invalidate the TLB of the IOMMU hardware as part of every > unmap() operation. > 1 - lazy mode. > Defer TLB invalidation so that the TLB of the IOMMU hardware > is invalidated periodically, rather than as part of every > unmap() operation. > > (generally, I think I'd s/non strict/lazy/ in this patch to avoid the double > negatives) > >> + >> 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..2cabd0c0a4f3 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_non_strict __read_mostly; >> >> struct iommu_callback_data { >> const struct iommu_ops *ops; >> @@ -131,6 +132,24 @@ 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_non_strict); >> + if (ret) >> + return ret; >> + >> + if (iommu_dma_non_strict) { >> + pr_warn("WARNING: iommu non-strict mode is chosen.\n" >> + "It's good for scatter-gather performance but lacks full isolation\n"); > > Hmm, not sure about this message either and tainting is probably over the > top. Maybe drop the taint and just pr_info something like "IOMMU DMA ops > using lazy TLB invalidation: unable to protect against malicious devices" > >> + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); >> + } >> + >> + return 0; >> +} >> +early_param("iommu.non_strict", iommu_dma_setup); >> + >> static ssize_t iommu_group_attr_show(struct kobject *kobj, >> struct attribute *__attr, char *buf) >> { >> @@ -1072,6 +1091,13 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev) >> group->default_domain = dom; >> if (!group->domain) >> group->domain = dom; >> + >> + if (dom && iommu_dma_non_strict) { >> + int attr = 1; >> + iommu_domain_set_attr(dom, >> + DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, >> + &attr); >> + } > > Hmm, I don't think we can guarantee that we're working with the DMA domain > here. Does this all fall out in the wash for the identity domain? Indeed so - for one, I expect drivers to reject it for anything that isn't their own default DMA ops domain type (as #5 and #6 do), and furthermore it only has any effect once iommu_dma_init_domain() reads it back if it stuck, and other domain types should never be getting passed into there anyway. Robin.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9871e649ffef..406b91759b62 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1749,6 +1749,19 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + iommu.non_strict= [ARM64] + Format: { "0" | "1" } + 0 - strict mode, default. + Release IOVAs after the related TLBs are invalid + completely. + 1 - non-strict mode. + Put off TLBs invalidation and release memory first. + It's good for scatter-gather performance but lacks + full isolation, an untrusted device can access the + reused memory because the TLBs may still valid. + Please take full consideration before choosing this + mode. Note that, VFIO will always use strict mode. + 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..2cabd0c0a4f3 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_non_strict __read_mostly; struct iommu_callback_data { const struct iommu_ops *ops; @@ -131,6 +132,24 @@ 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_non_strict); + if (ret) + return ret; + + if (iommu_dma_non_strict) { + pr_warn("WARNING: iommu non-strict mode is chosen.\n" + "It's good for scatter-gather performance but lacks full isolation\n"); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); + } + + return 0; +} +early_param("iommu.non_strict", iommu_dma_setup); + static ssize_t iommu_group_attr_show(struct kobject *kobj, struct attribute *__attr, char *buf) { @@ -1072,6 +1091,13 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev) group->default_domain = dom; if (!group->domain) group->domain = dom; + + if (dom && iommu_dma_non_strict) { + int attr = 1; + iommu_domain_set_attr(dom, + DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, + &attr); + } } ret = iommu_group_add_device(group, dev);