linux-kernel - Re: [PATCH v3 6/7] iommu/vt-d: Warn on out-of-range invalidation address

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Date:   Thu, 2 Jul 2020 06:43:41 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        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>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v3 6/7] iommu/vt-d: Warn on out-of-range invalidation
 address

Hi Eric,

On Thu, 2 Jul 2020 10:47:39 +0200
Auger Eric <eric.auger@...hat.com> wrote:

> Hi,
> 
> On 7/1/20 5:33 PM, 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.  
> What I don't really get is the guest shouldn't do that. Don't we want
> to be more strict in that case and return an error?
> 
My thinking is that the driver should behave the same level of leniency
as the HW. The other concern is that the consequence is severe, if TLB
invalidation failed, we have hang the guest to protect security.

> Thanks
> 
> Eric
> > 
> > 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 6a0c62c7395c..2e1b53ade784
> > 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;
> > +				pr_err_ratelimited("User address
> > not aligned, 0x%llx, size order %llu\n",
> > +
> > inv_info->addr_info.addr, size); }
> >  
> >  			/*
> >   
> 

[Jacob Pan]