linux-kernel - Re: [RFC PATCH v2 08/10] iommu/riscv: support nested iommu for flushing cache

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Date: Wed, 19 Jun 2024 13:17:40 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Zong Li <zong.li@...ive.com>
Cc: joro@...tes.org, will@...nel.org, robin.murphy@....com,
	tjeznach@...osinc.com, paul.walmsley@...ive.com, palmer@...belt.com,
	aou@...s.berkeley.edu, kevin.tian@...el.com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH v2 08/10] iommu/riscv: support nested iommu for
 flushing cache

On Fri, Jun 14, 2024 at 10:21:54PM +0800, Zong Li wrote:
> This patch implements cache_invalidate_user operation for the userspace
> to flush the hardware caches for a nested domain through iommufd.
> 
> Signed-off-by: Zong Li <zong.li@...ive.com>
> ---
>  drivers/iommu/riscv/iommu.c  | 90 ++++++++++++++++++++++++++++++++++--
>  include/uapi/linux/iommufd.h | 11 +++++
>  2 files changed, 97 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> index 410b236e9b24..d08eb0a2939e 100644
> --- a/drivers/iommu/riscv/iommu.c
> +++ b/drivers/iommu/riscv/iommu.c
> @@ -1587,8 +1587,9 @@ static int riscv_iommu_attach_dev_nested(struct iommu_domain *domain, struct dev
>  	if (riscv_iommu_bond_link(riscv_domain, dev))
>  		return -ENOMEM;
>  
> -	riscv_iommu_iotlb_inval(riscv_domain, 0, ULONG_MAX);
> -	info->dc_user.ta |= RISCV_IOMMU_PC_TA_V;
> +	if (riscv_iommu_bond_link(info->domain, dev))
> +		return -ENOMEM;

?? Is this in the wrong patch then? Confused

>  	riscv_iommu_iodir_update(iommu, dev, &info->dc_user);
>  
>  	info->domain = riscv_domain;
> @@ -1611,13 +1612,92 @@ static void riscv_iommu_domain_free_nested(struct iommu_domain *domain)
>  	kfree(riscv_domain);
>  }
>  
> +static int riscv_iommu_fix_user_cmd(struct riscv_iommu_command *cmd,
> +				    unsigned int pscid, unsigned int gscid)
> +{
> +	u32 opcode = FIELD_GET(RISCV_IOMMU_CMD_OPCODE, cmd->dword0);
> +
> +	switch (opcode) {
> +	case RISCV_IOMMU_CMD_IOTINVAL_OPCODE:
> +		u32 func = FIELD_GET(RISCV_IOMMU_CMD_FUNC, cmd->dword0);
> +
> +		if (func != RISCV_IOMMU_CMD_IOTINVAL_FUNC_GVMA &&
> +		    func != RISCV_IOMMU_CMD_IOTINVAL_FUNC_VMA) {
> +			pr_warn("The IOTINVAL function: 0x%x is not supported\n",
> +				func);
> +			return -EOPNOTSUPP;
> +		}
> +
> +		if (func == RISCV_IOMMU_CMD_IOTINVAL_FUNC_GVMA) {
> +			cmd->dword0 &= ~RISCV_IOMMU_CMD_FUNC;
> +			cmd->dword0 |= FIELD_PREP(RISCV_IOMMU_CMD_FUNC,
> +						  RISCV_IOMMU_CMD_IOTINVAL_FUNC_VMA);
> +		}
> +
> +		cmd->dword0 &= ~(RISCV_IOMMU_CMD_IOTINVAL_PSCID |
> +				 RISCV_IOMMU_CMD_IOTINVAL_GSCID);
> +		riscv_iommu_cmd_inval_set_pscid(cmd, pscid);
> +		riscv_iommu_cmd_inval_set_gscid(cmd, gscid);
> +		break;
> +	case RISCV_IOMMU_CMD_IODIR_OPCODE:
> +		/*
> +		 * Ensure the device ID is right. We expect that VMM has
> +		 * transferred the device ID to host's from guest's.
> +		 */

I'm not sure what this remark means, but I expect you will need to
translate any devices IDs from virtual to physical.

>  
>  static int
> -riscv_iommu_get_dc_user(struct device *dev, struct iommu_hwpt_riscv_iommu *user_arg)
> +riscv_iommu_get_dc_user(struct device *dev, struct iommu_hwpt_riscv_iommu *user_arg,
> +			struct riscv_iommu_domain *s1_domain)
>  {
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>  	struct riscv_iommu_device *iommu = dev_to_iommu(dev);
> @@ -1663,6 +1743,8 @@ riscv_iommu_get_dc_user(struct device *dev, struct iommu_hwpt_riscv_iommu *user_
>  		       riscv_iommu_get_dc(iommu, fwspec->ids[i]),
>  		       sizeof(struct riscv_iommu_dc));
>  		info->dc_user.fsc = dc.fsc;
> +		info->dc_user.ta = FIELD_PREP(RISCV_IOMMU_PC_TA_PSCID, s1_domain->pscid) |
> +					      RISCV_IOMMU_PC_TA_V;
>  	}

It is really weird that the s1 domain has any kind of id. What is the
PSCID? Is it analogous to VMID on ARM?

Jason