Re: [PATCH 6/7] iommu/vt-d: Warn on out-of-range invalidation address

[Lu Baolu]

Hi Jacob,

On 7/1/20 1:34 AM, Jacob Pan wrote:
> On Thu, 25 Jun 2020 18:10:43 +0800
> Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>  wrote:
>
> > Hi,
> >
> > On 2020/6/23 23:43, Jacob Pan wrote:
> > > For guest requested IOTLB invalidation, address and mask are
> > > provided as part of the invalidation data. VT-d HW silently ignores
> > > any address bits below the mask. SW shall also allow such case but
> > > give warning if address does not align with the mask. This patch
> > > relax the fault handling from error to warning and proceed with
> > > invalidation request with the given mask.
> > >
> > > Signed-off-by: Jacob Pan<jacob.jun.pan@xxxxxxxxxxxxxxx>
> > > ---
> > >    drivers/iommu/intel/iommu.c | 7 +++----
> > >    1 file changed, 3 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/iommu/intel/iommu.c
> > > b/drivers/iommu/intel/iommu.c index 5ea5732d5ec4..50fc62413a35
> > > 100644 --- a/drivers/iommu/intel/iommu.c
> > > +++ b/drivers/iommu/intel/iommu.c
> > > @@ -5439,13 +5439,12 @@ intel_iommu_sva_invalidate(struct
> > > iommu_domain *domain, struct device *dev,
> > >    		switch (BIT(cache_type)) {
> > >    		case IOMMU_CACHE_INV_TYPE_IOTLB:
> > > +			/* HW will ignore LSB bits based on
> > > address mask */ if (inv_info->granularity == IOMMU_INV_GRANU_ADDR &&
> > >    			    size &&
> > >    			    (inv_info->addr_info.addr &
> > > ((BIT(VTD_PAGE_SHIFT + size)) - 1))) {
> > > -				pr_err_ratelimited("Address out of
> > > range, 0x%llx, size order %llu\n",
> > > -
> > > inv_info->addr_info.addr, size);
> > > -				ret = -ERANGE;
> > > -				goto out_unlock;
> > > +				WARN_ONCE(1, "Address out of
> > > range, 0x%llx, size order %llu\n",
> > > +
> > > inv_info->addr_info.addr, size);
> > I don't think WARN_ONCE() is suitable here. It makes users think it's
> > a kernel bug. How about pr_warn_ratelimited()?
> I think pr_warn_ratelimited might still be too chatty. There is no
> functional issues, we just don't to silently ignore it. Perhaps just
> say:
> WARN_ONCE(1, "User provided address not page aligned, alignment forced")
> ?

WARN() is normally used for reporting a kernel bug. It dumps kernel
trace. And the users will report bug through bugzilla.kernel.org.

In this case, it's actually an unexpected user input, we shouldn't
treat it as a kernel bug and pr_err_ratelimited() is enough?

Best regards,
baolu