Messages in this thread Patch in this message | | | Date | Thu, 9 Mar 2023 17:17:10 -0800 | From | Nicolin Chen <> | Subject | Re: [PATCH v1 04/14] iommu/arm-smmu-v3: Add arm_smmu_hw_info |
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Hi Robin,
Thanks for the inputs.
On Thu, Mar 09, 2023 at 01:03:41PM +0000, Robin Murphy wrote: > External email: Use caution opening links or attachments > > > On 2023-03-09 10:53, Nicolin Chen wrote: > > This is used to forward the host IDR values to the user space, so the > > hypervisor and the guest VM can learn about the underlying hardware's > > capabilities. > > > > Also, set the driver_type to IOMMU_HW_INFO_TYPE_ARM_SMMUV3 to pass the > > corresponding type sanity in the core. > > > > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> > > --- > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 25 +++++++++++++++++++++ > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 ++ > > include/uapi/linux/iommufd.h | 14 ++++++++++++ > > 3 files changed, 41 insertions(+) > > > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > index f2425b0f0cd6..c1aac695ae0d 100644 > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > @@ -2005,6 +2005,29 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap) > > } > > } > > > > +static void *arm_smmu_hw_info(struct device *dev, u32 *length) > > +{ > > + struct arm_smmu_master *master = dev_iommu_priv_get(dev); > > + struct iommu_hw_info_smmuv3 *info; > > + void *base_idr; > > + int i; > > + > > + if (!master || !master->smmu) > > + return ERR_PTR(-ENODEV); > > + > > + info = kzalloc(sizeof(*info), GFP_KERNEL); > > + if (!info) > > + return ERR_PTR(-ENOMEM); > > + > > + base_idr = master->smmu->base + ARM_SMMU_IDR0; > > + for (i = 0; i <= 5; i++) > > + info->idr[i] = readl_relaxed(base_idr + 0x4 * i); > > You need to take firmware overrides etc. into account here. In > particular, features like BTM may need to be hidden to work around > errata either in the system integration or the SMMU itself. It isn't > reasonable to expect every VMM to be aware of every erratum and > workaround, and there may even be workarounds where we need to go out of > our way to prevent guests from trying to use certain features in order > to maintain correctness at S2.
We can add a bit of overrides after this for errata, perhaps?
I have some trouble with finding the errata docs. Would it be possible for you to direct me to it with a link maybe?
> In general this should probably follow the same principle as KVM, where > we only expose sanitised feature registers representing the > functionality the host understands. Code written today is almost > guaranteed to be running on hardware released in 2030, at least *somewhere*.
Yes.
Thanks Nicolin
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