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

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Message-ID: <0f704b87-aad7-c864-91ac-423a05287f21@linux.intel.com>
Date:   Wed, 18 Dec 2019 11:25:27 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     baolu.lu@...ux.intel.com, "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>
Subject: Re: [PATCH v8 06/10] iommu/vt-d: Cache virtual command capability
 register

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?

Best regards,
baolu

> +
>   /* IOTLB_REG */
>   #define DMA_TLB_FLUSH_GRANU_OFFSET  60
>   #define DMA_TLB_GLOBAL_FLUSH (((u64)1) << 60)
> @@ -531,6 +534,7 @@ 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 */
>