linux-kernel - Re: [PATCH] wifi: ath11k: workaround to use VMs

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Date: Thu, 21 Mar 2024 13:13:31 -0700
From: Jeff Johnson <quic_jjohnson@...cinc.com>
To: Jose Ignacio Tornos Martinez <jtornosm@...hat.com>, <kvalo@...nel.org>,
        <jjohnson@...nel.org>, <linux-wireless@...r.kernel.org>,
        <ath11k@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        "kernel@...cinc.com" <kernel@...cinc.com>
CC: <quic_bqiang@...cinc.com>
Subject: Re: [PATCH] wifi: ath11k: workaround to use VMs

On 3/21/2024 10:23 AM, Jose Ignacio Tornos Martinez wrote:
> Currently, this driver is not working when the device is handled in a
> Virtual Machine (PCI pass-through), as it was already reported here:
> https://lore.kernel.org/all/fc6bd06f-d52b-4dee-ab1b-4bb845cc0b95@quicinc.com/T/
> Baochen Qiang focused the problem and described how to have it working
> for a specific real MSI vector from host that needs to be used in VM too.
> And this value, as it was commented, can change.
> 
> The problem seems complex to me and I don't know if there is any easy way
> to solve it. Meanwhile and using the information from Baochen Qiang,
> since the use of VMs is very interesting for testing procedures,
> I would like to just add this workaround that consists on adding a
> parameter to pass the real MSI vector from host to the VM. In that way,
> checking the 'lscpi' command output from host, it could be handled manually
> or with some user tool in order to have the VM with the driver working.
> Of course, if this parameter is not configured (zero value and default),
> we will have the same behavior as always.
> 
> Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@...hat.com>
> ---
>  drivers/net/wireless/ath/ath11k/pci.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/pci.c b/drivers/net/wireless/ath/ath11k/pci.c
> index be9d2c69cc41..0e322956b10f 100644
> --- a/drivers/net/wireless/ath/ath11k/pci.c
> +++ b/drivers/net/wireless/ath/ath11k/pci.c
> @@ -31,6 +31,11 @@
>  
>  #define TCSR_SOC_HW_SUB_VER	0x1910010
>  
> +static ulong ath11k_host_msi_addr = 0;
> +module_param_named(host_msi_addr, ath11k_host_msi_addr, ulong, 0644);
> +MODULE_PARM_DESC(host_msi_addr,
> +		 "Workaround to configure the MSI address that is used from host in order to be used in VM");
> +
>  static const struct pci_device_id ath11k_pci_id_table[] = {
>  	{ PCI_VDEVICE(QCOM, QCA6390_DEVICE_ID) },
>  	{ PCI_VDEVICE(QCOM, WCN6855_DEVICE_ID) },
> @@ -443,6 +448,18 @@ static int ath11k_pci_alloc_msi(struct ath11k_pci *ab_pci)
>  
>  	ath11k_pci_msi_disable(ab_pci);
>  
> +	if (ath11k_host_msi_addr) {
> +		ab_pci->ab->pci.msi.ep_base_data = 0;
> +		ab->pci.msi.addr_hi = (u32)(ath11k_host_msi_addr >> 32);
> +		ab->pci.msi.addr_lo = (u32)(ath11k_host_msi_addr & 0xffffffff);
> +
> +		ath11k_dbg(ab, ATH11K_DBG_PCI, "msi addr hi 0x%x lo 0x%x base data is %d\n",
> +			   ab->pci.msi.addr_hi,
> +			   ab->pci.msi.addr_lo,
> +			   ab->pci.msi.ep_base_data);
> +		return 0;
> +	}
> +
>  	msi_desc = irq_get_msi_desc(ab_pci->pdev->irq);
>  	if (!msi_desc) {
>  		ath11k_err(ab, "msi_desc is NULL!\n");
> @@ -482,6 +499,9 @@ static int ath11k_pci_config_msi_data(struct ath11k_pci *ab_pci)
>  {
>  	struct msi_desc *msi_desc;
>  
> +	if (ath11k_host_msi_addr)
> +		return 0;
> +
>  	msi_desc = irq_get_msi_desc(ab_pci->pdev->irq);
>  	if (!msi_desc) {
>  		ath11k_err(ab_pci->ab, "msi_desc is NULL!\n");

+ kernel@...cinc.com to make sure the Qualcomm VM experts are aware of this
issue and to see if they have any additional suggestions.