linux-kernel - Re: [PATCH] VMCI: Add support for ARM64

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Date:   Fri, 06 May 2022 16:13:57 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     vdasa@...are.com
Cc:     pv-drivers@...are.com, linux-kernel-review@...are.com,
        Cyprien Laplace <claplace@...are.com>,
        Vishnu Dasa <vdasa@...are.com>,
        Bryan Tan <bryantan@...are.com>, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] VMCI: Add support for ARM64

vdasa@...are.com writes:

> From: Vishnu Dasa <vdasa@...are.com>
>
> Add support for ARM64 architecture so that the driver can now be built
> and VMCI device can be used.
>
> Update Kconfig file to allow the driver to be built on ARM64 as well.
> Fail vmci_guest_probe_device() on ARM64 if the device does not support
> MMIO register access.  Lastly, add virtualization specific barriers
> which map to actual memory barrier instructions on ARM64, because it
> is required in case of ARM64 for queuepair (de)queuing.
>

FWIW, it seems you're doing three things at once, better split this into
a 3-patch series.

> Reviewed-by: Bryan Tan <bryantan@...are.com>
> Reviewed-by: Cyprien Laplace <claplace@...are.com>
> Signed-off-by: Vishnu Dasa <vdasa@...are.com>
> ---
>  drivers/misc/vmw_vmci/Kconfig           |  2 +-
>  drivers/misc/vmw_vmci/vmci_guest.c      |  4 ++++
>  drivers/misc/vmw_vmci/vmci_queue_pair.c | 12 ++++++++++++
>  3 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/vmw_vmci/Kconfig b/drivers/misc/vmw_vmci/Kconfig
> index 605794aadf11..b6d4d7fd686a 100644
> --- a/drivers/misc/vmw_vmci/Kconfig
> +++ b/drivers/misc/vmw_vmci/Kconfig
> @@ -5,7 +5,7 @@
>  
>  config VMWARE_VMCI
>  	tristate "VMware VMCI Driver"
> -	depends on X86 && PCI
> +	depends on (X86 || ARM64) && !CPU_BIG_ENDIAN && PCI
>  	help
>  	  This is VMware's Virtual Machine Communication Interface.  It enables
>  	  high-speed communication between host and guest in a virtual
> diff --git a/drivers/misc/vmw_vmci/vmci_guest.c b/drivers/misc/vmw_vmci/vmci_guest.c
> index 57a6157209a1..aa7b05de97dd 100644
> --- a/drivers/misc/vmw_vmci/vmci_guest.c
> +++ b/drivers/misc/vmw_vmci/vmci_guest.c
> @@ -614,6 +614,10 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>  	}
>  
>  	if (!mmio_base) {
> +		if (IS_ENABLED(CONFIG_ARM64)) {
> +			dev_err(&pdev->dev, "MMIO base is invalid\n");
> +			return -ENXIO;
> +		}
>  		error = pcim_iomap_regions(pdev, BIT(0), KBUILD_MODNAME);
>  		if (error) {
>  			dev_err(&pdev->dev, "Failed to reserve/map IO regions\n");
> diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.c b/drivers/misc/vmw_vmci/vmci_queue_pair.c
> index 94ebf7f3fd58..8f2de1893245 100644
> --- a/drivers/misc/vmw_vmci/vmci_queue_pair.c
> +++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
> @@ -2577,6 +2577,12 @@ static ssize_t qp_enqueue_locked(struct vmci_queue *produce_q,
>  	if (result < VMCI_SUCCESS)
>  		return result;
>  
> +	/*
> +	 * This virt_wmb() ensures that data written to the queue
> +	 * is observable before the new producer_tail is.
> +	 */
> +	virt_wmb();
> +
>  	vmci_q_header_add_producer_tail(produce_q->q_header, written,
>  					produce_q_size);
>  	return written;
> @@ -2620,6 +2626,12 @@ static ssize_t qp_dequeue_locked(struct vmci_queue *produce_q,
>  	if (buf_ready < VMCI_SUCCESS)
>  		return (ssize_t) buf_ready;
>  
> +	/*
> +	 * This virt_rmb() ensures that data from the queue will be read
> +	 * after we have determined how much is ready to be consumed.
> +	 */
> +	virt_rmb();
> +
>  	read = (size_t) (buf_ready > buf_size ? buf_size : buf_ready);
>  	head = vmci_q_header_consumer_head(produce_q->q_header);
>  	if (likely(head + read < consume_q_size)) {

-- 
Vitaly