linux-kernel - Re: [PATCH v8 06/10] iommu/vt-d: Cache virtual command capability register

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Message-ID: <20200109135903.74b0220f@jacob-builder>
Date:   Thu, 9 Jan 2020 13:59:03 -0800
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>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v8 06/10] iommu/vt-d: Cache virtual command capability
 register

On Wed, 18 Dec 2019 11:25:27 +0800
Lu Baolu <baolu.lu@...ux.intel.com> wrote:

> Hi,
> 
> On 12/17/19 3:24 AM, Jacob Pan wrote:
> > Virtual command registers are used in the guest only, to prevent
> > vmexit cost, we cache the capability and store it during
> > initialization.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >   drivers/iommu/dmar.c        | 1 +
> >   include/linux/intel-iommu.h | 4 ++++
> >   2 files changed, 5 insertions(+)
> > 
> > diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> > index f2f5d75da94a..3f98dd9ad004 100644
> > --- a/drivers/iommu/dmar.c
> > +++ b/drivers/iommu/dmar.c
> > @@ -953,6 +953,7 @@ static int map_iommu(struct intel_iommu *iommu,
> > u64 phys_addr) warn_invalid_dmar(phys_addr, " returns all ones");
> >   		goto unmap;
> >   	}
> > +	iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);
> >   
> >   	/* the registers might be more than one page */
> >   	map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),
> > diff --git a/include/linux/intel-iommu.h
> > b/include/linux/intel-iommu.h index ee26989df008..4d25141ec3df
> > 100644 --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -189,6 +189,9 @@
> >   #define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
> >   #define ecap_sc_support(e)	((e >> 7) & 0x1) /* Snooping
> > Control */ 
> > +/* Virtual command interface capabilities */
> > +#define vccap_pasid(v)		((v & DMA_VCS_PAS)) /* PASID
> > allocation */  
> 
> Has DMA_VCS_PAS ever been defined?
> 
Good catch, it is in the next patch, need to move the #define here.
Thanks!

> Best regards,
> baolu
> 
>  [...]  

[Jacob Pan]