netdev - Re: [PATCH v3 12/20] efx: use acquire_endpoint when looking for free HPA

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Message-ID: <339d40b0-95f7-4174-9d0e-a954dc23c164@intel.com>
Date: Thu, 12 Sep 2024 16:09:21 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: alejandro.lucero-palau@....com, linux-cxl@...r.kernel.org,
 netdev@...r.kernel.org, dan.j.williams@...el.com, martin.habets@...inx.com,
 edward.cree@....com, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com
Cc: Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v3 12/20] efx: use acquire_endpoint when looking for free
 HPA



On 9/7/24 1:18 AM, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Asking for availbale HPA space is the previous step to try to obtain
> an HPA range suitable to accel driver purposes.
> 
> Add this call to efx cxl initialization and use acquire_endpoint for
> avoiding potential races with cxl port creation.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> ---
>  drivers/net/ethernet/sfc/efx.c     |  8 +++++++-
>  drivers/net/ethernet/sfc/efx_cxl.c | 32 ++++++++++++++++++++++++++++++
>  2 files changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
> index 3a7406aa950c..08a2f527df16 100644
> --- a/drivers/net/ethernet/sfc/efx.c
> +++ b/drivers/net/ethernet/sfc/efx.c
> @@ -1117,10 +1117,16 @@ static int efx_pci_probe(struct pci_dev *pci_dev,
>  	 * used for PIO buffers. If there is no CXL support, or initialization
>  	 * fails, efx_cxl_pio_initialised wll be false and legacy PIO buffers
>  	 * defined at specific PCI BAR regions will be used.
> +	 *
> +	 * The only error to handle is -EPROBE_DEFER happening if the root port
> +	 * is not there yet.
>  	 */
>  	rc = efx_cxl_init(efx);
> -	if (rc)
> +	if (rc) {
> +		if (rc == -EPROBE_DEFER)
> +			goto fail2;
>  		pci_err(pci_dev, "CXL initialization failed with error %d\n", rc);
> +	}
>  
>  	rc = efx_pci_probe_post_io(efx);
>  	if (rc) {
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 899bc823a212..826759caa552 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -23,6 +23,7 @@ int efx_cxl_init(struct efx_nic *efx)
>  	struct pci_dev *pci_dev = efx->pci_dev;
>  	struct efx_cxl *cxl;
>  	struct resource res;
> +	resource_size_t max;
>  	u16 dvsec;
>  	int rc;
>  
> @@ -90,7 +91,38 @@ int efx_cxl_init(struct efx_nic *efx)
>  		goto err;
>  	}
>  
> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
> +	if (IS_ERR(cxl->endpoint)) {
> +		rc = PTR_ERR(cxl->endpoint);
> +		if (rc != -EPROBE_DEFER) {
> +			pci_err(pci_dev, "CXL accel acquire endpoint failed");
> +			goto err;
> +		}

What happens if (rc == -EPROBE_DEFER)? Here it drops down but you don't have a valid cxl->endpoint when cxl_get_hpa_freespace() is called.

DJ
 
> +	}
> +
> +	cxl->cxlrd = cxl_get_hpa_freespace(cxl->endpoint,
> +					   CXL_DECODER_F_RAM | CXL_DECODER_F_TYPE2,
> +					   &max);
> +
> +	if (IS_ERR(cxl->cxlrd)) {
> +		pci_err(pci_dev, "cxl_get_hpa_freespace failed\n");
> +		rc = PTR_ERR(cxl->cxlrd);
> +		goto err_release;
> +	}
> +
> +	if (max < EFX_CTPIO_BUFFER_SIZE) {
> +		pci_err(pci_dev, "%s: no enough free HPA space %llu < %u\n",
> +			__func__, max, EFX_CTPIO_BUFFER_SIZE);
> +		rc = -ENOSPC;
> +		goto err;
> +	}
> +
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
> +
>  	return 0;
> +
> +err_release:
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
>  err:
>  	kfree(cxl->cxlds);
>  	kfree(cxl);