Re: [PATCH v11 08/10] iommu/vt-d: Cache virtual command capability register

From: Auger Eric <eric.auger@redhat.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	iommu@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH v11 08/10] iommu/vt-d: Cache virtual command capability register
Date: Thu, 9 Apr 2020 12:14:31 +0200	[thread overview]
Message-ID: <43e7452c-dea8-934c-105e-05798cb1d225@redhat.com> (raw)
In-Reply-To: <1585939334-21396-9-git-send-email-jacob.jun.pan@linux.intel.com>

Hi Jacob,

On 4/3/20 8:42 PM, 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@linux.intel.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
nit: following Joerg's comment on 02/10, may be worth squashing it into
the patch that uses it (10/10)

Thanks

Eric
> 
> ---
> v7 Reviewed by Eric & Baolu
> ---
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  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 f775bb825343..e02a96848586 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 capability */
> +#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 {									\
> @@ -562,6 +566,7 @@ 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 */
> 

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