linux-kernel - Re: [RFC PATCH v1 14/38] coco: host: arm64: Device communication support

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Message-ID: <20250804222952.GA3645019@bhelgaas>
Date: Mon, 4 Aug 2025 17:29:52 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Cc: linux-coco@...ts.linux.dev, kvmarm@...ts.linux.dev,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	aik@....com, lukas@...ner.de, Samuel Ortiz <sameo@...osinc.com>,
	Xu Yilun <yilun.xu@...ux.intel.com>, Jason Gunthorpe <jgg@...pe.ca>,
	Suzuki K Poulose <Suzuki.Poulose@....com>,
	Steven Price <steven.price@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: [RFC PATCH v1 14/38] coco: host: arm64: Device communication
 support

On Mon, Jul 28, 2025 at 07:21:51PM +0530, Aneesh Kumar K.V (Arm) wrote:
> Add helpers for device communication from RMM

> +++ b/drivers/virt/coco/arm-cca-host/rmm-da.c
> +static int __do_dev_communicate(int type, struct pci_tsm *tsm)
> +{

> +			/* FIXME!! depending on the DevComms status,
> +			 * it might require to ABORT the communcation.

s/communcation/communication/

Even better, fix the FIXME :)

> +			 */
> +			return -EINVAL;
> +		}
> +
> +		if (io_exit->cache_rsp_len > cache_remaining)
> +			return -EINVAL;
> +
> +		memcpy(cache_buf + *cache_offset,
> +		       (comm_data->resp_buff + io_exit->cache_rsp_offset), io_exit->cache_rsp_len);
> +		*cache_offset += io_exit->cache_rsp_len;
> +	}
> +
> +	/*
> +	 * wait for last packet request from RMM.
> +	 * We should not find this because our device communication in synchronous

s/communication in/communication is/

> +	 */
> +	if (io_exit->flags & RMI_DEV_COMM_EXIT_WAIT)
> +		return -ENXIO;
> +
> +	is_multi = !!(io_exit->flags & RMI_DEV_COMM_EXIT_MULTI);
> +
> +	/* next packet to send */
> +	if (io_exit->flags & RMI_DEV_COMM_EXIT_SEND) {
> +		nbytes = doe_send_req_resp(tsm);
> +		if (nbytes < 0) {
> +			/* report error back to RMM */
> +			io_enter->status = RMI_DEV_COMM_ERROR;
> +		} else {
> +			/* send response back to RMM */
> +			io_enter->resp_len = nbytes;
> +			io_enter->status = RMI_DEV_COMM_RESPONSE;
> +		}
> +	} else {
> +		/* no data transmitted => no data received */
> +		io_enter->resp_len = 0;
> +	}
> +
> +	/* The call need to do multiple request/respnse */

s/respnse/response/

> +	if (is_multi)
> +		goto redo_communicate;
> +
> +	return 0;
> +}