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Date:   Tue, 30 Jun 2020 10:34:59 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 6/7] iommu/vt-d: Warn on out-of-range invalidation
 address

On Thu, 25 Jun 2020 18:10:43 +0800
Lu Baolu <baolu.lu@...ux.intel.com> 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@...ux.intel.com>
> > ---
> >   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")
?

> Best regards,
> baolu
> 
> >   			}
> >   
> >   			/*
> >   

[Jacob Pan]

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