netdev - Re: [PATCH v4 02/17] octeontx2-pf: Mailbox communication with AF

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Date:   Tue, 21 Jan 2020 08:00:29 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     sunil.kovvuri@...il.com
Cc:     netdev@...r.kernel.org, davem@...emloft.net, mkubecek@...e.cz,
        Sunil Goutham <sgoutham@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Christina Jacob <cjacob@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        Aleksey Makarov <amakarov@...vell.com>
Subject: Re: [PATCH v4 02/17] octeontx2-pf: Mailbox communication with AF

On Tue, 21 Jan 2020 18:51:36 +0530, sunil.kovvuri@...il.com wrote:
> From: Sunil Goutham <sgoutham@...vell.com>
> 
> In the resource virtualization unit (RVU) each of the PF and AF
> (admin function) share a 64KB of reserved memory region for
> communication. This patch initializes PF <=> AF mailbox IRQs,
> registers handlers for processing these communication messages.
> Also adds support to process these messages in both directions
> ie responses to PF initiated DOWN (PF => AF) messages and AF
> initiated UP messages (AF => PF).
> 
> Mbox communication APIs and message formats are defined in AF driver
> (drivers/net/ethernet/marvell/octeontx2/af), mbox.h from AF driver is
> included here to avoid duplication.
> 
> Signed-off-by: Geetha sowjanya <gakula@...vell.com>
> Signed-off-by: Christina Jacob <cjacob@...vell.com>
> Signed-off-by: Subbaraya Sundeep <sbhatta@...vell.com>
> Signed-off-by: Aleksey Makarov <amakarov@...vell.com>
> Signed-off-by: Sunil Goutham <sgoutham@...vell.com>

> +struct  mbox {
         ^^
> +	struct otx2_mbox	mbox;
> +	struct work_struct	mbox_wrk;
> +	struct otx2_mbox	mbox_up;
> +	struct work_struct	mbox_up_wrk;
> +	struct otx2_nic		*pfvf;
> +	void			*bbuf_base; /* Bounce buffer for mbox memory */
> +	struct mutex		lock;	/* serialize mailbox access */
> +	int			num_msgs; /*mbox number of messages*/
                                           ^                       ^
> +	int			up_num_msgs;/* mbox_up number of messages*/
                                            ^                            ^
> +};
>  
>  struct otx2_hw {
>  	struct pci_dev		*pdev;
>  	u16                     rx_queues;
>  	u16                     tx_queues;
>  	u16			max_queues;
> +
> +	/* MSI-X*/
                ^

The white space here is fairly loose 

> +	char			*irq_name;
> +	cpumask_var_t           *affinity_mask;
>  };
>  

> +static inline void otx2_sync_mbox_bbuf(struct otx2_mbox *mbox, int devid)
> +{
> +	u16 msgs_offset = ALIGN(sizeof(struct mbox_hdr), MBOX_MSG_ALIGN);
> +	void *hw_mbase = mbox->hwbase + (devid * MBOX_SIZE);
> +	struct otx2_mbox_dev *mdev = &mbox->dev[devid];
> +	struct mbox_hdr *hdr;
> +	u64 msg_size;
> +
> +	if (mdev->mbase == hw_mbase)
> +		return;
> +
> +	hdr = hw_mbase + mbox->rx_start;
> +	msg_size = hdr->msg_size;
> +
> +	if (msg_size > mbox->rx_size - msgs_offset)
> +		msg_size = mbox->rx_size - msgs_offset;
> +
> +	/* Copy mbox messages from mbox memory to bounce buffer */
> +	memcpy(mdev->mbase + mbox->rx_start,
> +	       hw_mbase + mbox->rx_start, msg_size + msgs_offset);

I'm slightly concerned about the use of non-iomem helpers like memset
and memcpy on what I understand to be IOMEM, and the lack of memory
barriers. But then again, I don't know much about iomem_wc(), is this
code definitely correct from memory ordering perspective?
(The memory barrier in otx2_mbox_msg_send() should probably be just
wmb(), syncing with HW is unrelated with SMP.)