linux-kernel - Re: [PATCH V10 09/11] iommu/vt-d: Cache virtual command capability register

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Date:   Tue, 31 Mar 2020 15:33:27 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Alex Williamson" <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH V10 09/11] iommu/vt-d: Cache virtual command capability
 register

On Sat, 28 Mar 2020 10:04:38 +0000
"Tian, Kevin" <kevin.tian@...el.com> wrote:

> > From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > Sent: Saturday, March 21, 2020 7:28 AM
> > 
> > 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>
> > Reviewed-by: Eric Auger <eric.auger@...hat.com>
> > Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> > 
> > ---
> > v7 Reviewed by Eric & Baolu
> > ---
> > ---
> >  drivers/iommu/dmar.c        | 1 +
> >  include/linux/intel-iommu.h | 5 +++++
> >  2 files changed, 6 insertions(+)
> > 
> > diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> > index 4d6b7b5b37ee..3b36491c8bbb 100644
> > --- a/drivers/iommu/dmar.c
> > +++ b/drivers/iommu/dmar.c
> > @@ -963,6 +963,7 @@ 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 43539713b3b3..ccbf164fb711
> > 100644 --- a/include/linux/intel-iommu.h
> > +++ b/include/linux/intel-iommu.h
> > @@ -194,6 +194,9 @@
> >  #define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
> >  #define ecap_sc_support(e)	((e >> 7) & 0x1) /* Snooping
> > Control */
> > 
> > +/* Virtual command interface capabilities */  
> 
> capabilities -> capability
Will do, I was thinking the future :)

Thanks,

Jacob
> 
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> 
> > +#define vccap_pasid(v)		((v & DMA_VCS_PAS)) /* PASID
> > allocation */
> > +
> >  /* IOTLB_REG */
> >  #define DMA_TLB_FLUSH_GRANU_OFFSET  60
> >  #define DMA_TLB_GLOBAL_FLUSH (((u64)1) << 60)
> > @@ -287,6 +290,7 @@
> > 
> >  /* PRS_REG */
> >  #define DMA_PRS_PPR	((u32)1)
> > +#define DMA_VCS_PAS	((u64)1)
> > 
> >  #define IOMMU_WAIT_OP(iommu, offset, op, cond, sts)
> > 	\
> >  do
> > {
> > \ @@ -537,6 +541,7 @@ struct intel_iommu { u64
> > reg_size; /* size of hw register set */ u64		cap;
> >  	u64		ecap;
> > +	u64		vccap;
> >  	u32		gcmd; /* Holds TE, EAFL. Don't need
> > SRTP, SFL, WBF */
> >  	raw_spinlock_t	register_lock; /* protect register
> > handling */ int		seq_id;	/* sequence id of the
> > iommu */ --
> > 2.7.4  
> 

[Jacob Pan]