Re: [PATCH RFC RESEND 6/6] iommu/riscv: support nested iommu for flushing cache

From: Jason Gunthorpe
Date: Tue May 07 2024 - 11:08:53 EST


On Tue, May 07, 2024 at 10:26:00PM +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@xxxxxxxxxx>
> ---
> drivers/iommu/riscv/iommu.c | 91 ++++++++++++++++++++++++++++++++++++
> include/uapi/linux/iommufd.h | 9 ++++
> 2 files changed, 100 insertions(+)
>
> diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> index 7eda850df475..4dd58fe2242d 100644
> --- a/drivers/iommu/riscv/iommu.c
> +++ b/drivers/iommu/riscv/iommu.c
> @@ -1522,9 +1522,100 @@ 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.
> + */
> + break;
> + default:
> + pr_warn("The user command: 0x%x is not supported\n", opcode);
> + return -EOPNOTSUPP;

No userspace triggerable warnings.

> +static int riscv_iommu_cache_invalidate_user(struct iommu_domain *domain,
> + struct iommu_user_data_array *array)
> +{
> + struct riscv_iommu_domain *riscv_domain = iommu_domain_to_riscv(domain);
> + struct riscv_iommu_device *iommu;
> + struct riscv_iommu_bond *bond;
> + struct riscv_iommu_command cmd;
> + struct iommu_hwpt_riscv_iommu_invalidate inv_info;
> + int ret, index;
> +
> + if (!riscv_domain)
> + return -EINVAL;
> +
> + /* Assume attached devices in the domain go through the same IOMMU device */

No, you can't assume that.

Jason