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

[Jacob Pan]

On Wed, 1 Jul 2020 09:45:40 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> 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?
> 
Sounds good. I will leave it.

Thanks,

Jacob
> Best regards,
> baolu

[Jacob Pan]