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

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Message-ID: <f5a2ffda-a243-ed20-63e0-50d784d3af71@linux.intel.com>
Date:   Wed, 1 Jul 2020 09:45:40 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     baolu.lu@...ux.intel.com, 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>
Subject: Re: [PATCH 6/7] iommu/vt-d: Warn on out-of-range invalidation address

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@...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")
> ?
> 

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