linux-kernel - Re: [PATCH v2 04/10] iommu/vt-d: Match CPU and IOMMU paging mode

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Date:   Mon, 18 Nov 2019 13:52:38 -0800
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>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 04/10] iommu/vt-d: Match CPU and IOMMU paging mode

On Mon, 18 Nov 2019 21:55:03 +0100
Auger Eric <eric.auger@...hat.com> wrote:

> Hi Jacob,
> 
> On 11/18/19 8:42 PM, Jacob Pan wrote:
> > When setting up first level page tables for sharing with CPU, we
> > need to ensure IOMMU can support no less than the levels supported
> > by the CPU.
> > It is not adequate, as in the current code, to set up 5-level paging
> > in PASID entry First Level Paging Mode(FLPM) solely based on CPU.
> > 
> > Fixes: 437f35e1cd4c8 ("iommu/vt-d: Add first level page table
> > interface")
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>
> > ---
> >  drivers/iommu/intel-pasid.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iommu/intel-pasid.c
> > b/drivers/iommu/intel-pasid.c index 040a445be300..e7cb0b8a7332
> > 100644 --- a/drivers/iommu/intel-pasid.c
> > +++ b/drivers/iommu/intel-pasid.c
> > @@ -499,8 +499,16 @@ int intel_pasid_setup_first_level(struct
> > intel_iommu *iommu, }
> >  
> >  #ifdef CONFIG_X86
> > -	if (cpu_feature_enabled(X86_FEATURE_LA57))
> > -		pasid_set_flpm(pte, 1);
> > +	/* Both CPU and IOMMU paging mode need to match */
> > +	if (cpu_feature_enabled(X86_FEATURE_LA57)) {
> > +		if (cap_5lp_support(iommu->cap)) {
> > +			pasid_set_flpm(pte, 1);
> > +		} else {
> > +			pr_err("VT-d has no 5-level paging support
> > for CPU\n");
> > +			pasid_clear_entry(pte);
> > +			return -EINVAL;  
> Can it happen? If I am not wrong intel_pasid_setup_first_level() only
> seems to be called from intel_svm_bind_mm which now checks the
> SVM_CAPABLE flag.
> 
You are right, this check is not needed any more. I will drop the patch.
> Thanks
> 
> Eric
> > +		}
> > +	}
> >  #endif /* CONFIG_X86 */
> >  
> >  	pasid_set_domain_id(pte, did);
> >   
> 

[Jacob Pan]