linux-kernel - RE: [PATCH RFCv1 12/14] iommufd: Add IOMMUFD_OBJ_VQUEUE and IOMMUFD_CMD_VQUEUE

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Date: Thu, 23 May 2024 07:05:28 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "will@...nel.org" <will@...nel.org>,
	"robin.murphy@....com" <robin.murphy@....com>, "jgg@...dia.com"
	<jgg@...dia.com>, "suravee.suthikulpanit@....com"
	<suravee.suthikulpanit@....com>
CC: "joro@...tes.org" <joro@...tes.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-tegra@...r.kernel.org"
	<linux-tegra@...r.kernel.org>, "Liu, Yi L" <yi.l.liu@...el.com>,
	"eric.auger@...hat.com" <eric.auger@...hat.com>, "vasant.hegde@....com"
	<vasant.hegde@....com>, "jon.grimm@....com" <jon.grimm@....com>,
	"santosh.shukla@....com" <santosh.shukla@....com>, "Dhaval.Giani@....com"
	<Dhaval.Giani@....com>, "shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>
Subject: RE: [PATCH RFCv1 12/14] iommufd: Add IOMMUFD_OBJ_VQUEUE and
 IOMMUFD_CMD_VQUEUE_ALLOC

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Saturday, April 13, 2024 11:47 AM
> +
> +/**
> + * struct iommu_vqueue_tegra241_cmdqv - NVIDIA Tegra241's Virtual
> Command Queue
> + *                                      for its CMDQV Extension for ARM SMMUv3
> + *                                      (IOMMU_VQUEUE_DATA_TEGRA241_CMDQV)
> + * @vcmdq_id: logical ID of a virtual command queue in the VIOMMU
> instance
> + * @vcmdq_log2size: (1 << @vcmdq_log2size) will be the size of the vcmdq
> + * @vcmdq_base: guest physical address (IPA) to the vcmdq base address
> + */
> +struct iommu_vqueue_tegra241_cmdqv {
> +	__u32 vcmdq_id;
> +	__u32 vcmdq_log2size;
> +	__aligned_u64 vcmdq_base;
> +};

Is there restriction that log2size cannot exceed 12?

According to patch14:

+	q_base = arm_smmu_domain_ipa_to_pa(vintf->s2_domain, arg.vcmdq_base);
+	vcmdq->cmdq.q.q_base  = q_base & VCMDQ_ADDR;
+	vcmdq->cmdq.q.q_base |=	arg.vcmdq_log2size;

It only converts the IPA to HPA for the starting page, assuming
continuous host pages backing a guest cmd queue including
multiple pages. but what guarantees it?