linux-kernel - Re: [PATCH 1/2] PCI: endpoint: Enhance pci_epf_alloc_space() and rename to pci_epf_set_inbound

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Message-ID: <1624f0d5-4ee9-496d-b51e-0ad3ac1c00b9@oracle.com>
Date: Fri, 29 Aug 2025 22:51:56 +0530
From: ALOK TIWARI <alok.a.tiwari@...cle.com>
To: Frank Li <Frank.Li@....com>, Manivannan Sadhasivam <mani@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>, Allen Hubbe <allenbh@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ntb@...ts.linux.dev
Subject: Re: [PATCH 1/2] PCI: endpoint: Enhance pci_epf_alloc_space() and
 rename to pci_epf_set_inbound_space()



On 8/16/2025 3:50 AM, Frank Li wrote:
> +int pci_epf_set_inbound_space(struct pci_epf *epf, size_t size,
> +			      enum pci_barno bar,
> +			      const struct pci_epc_features *epc_features,
> +			      enum pci_epc_interface_type type,
> +			      bool from_memory,
> +			      dma_addr_t inbound_addr)
>   {
>   	u64 bar_fixed_size = epc_features->bar[bar].fixed_size;
>   	size_t aligned_size, align = epc_features->align;
> @@ -270,7 +276,32 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
>   	dma_addr_t phys_addr;
>   	struct pci_epc *epc;
>   	struct device *dev;
> -	void *space;
> +	void *space = NULL;
> +	dma_addr_t up;
> +
> +	up = inbound_addr + size - 1;
> +
> +	/*
> +	 *  Bits:            15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
> +	 *  Inbound_addr:    U  U  U  U  U  U  0 X X X X X X X X X
> +	 *  Up:              U  U  U  U  U  U  1 X X X X X X X X X
> +	 *
> +	 *  U means address bits have not change in Range [Inbound_Addr, Up]
> +	 *  X means bit 0 or 1.
> +	 *
> +	 *  Inbound_addr^Up  0  0  0  0  0  0  1 X X X X X X X X X
> +	 *  Find first bit 1 pos from MSB, 2 ^ pos windows will cover
> +	 *  [Inbound_Addr, Up] range.
> +	 */
> +	if (!from_memory) {
> +		int pos;
> +
> +		for (pos = sizeof(dma_addr_t) - 1; pos > 0; pos--)
> +			if ((up ^ inbound_addr) & BIT_ULL(pos))
> +				break;
> +

sizeof(dma_addr_t) returns bytes, not bits.
so 7..1 time loop in enough here ?

> +		size = 1 << pos;
> +	}
>   
>   	if (size < 128)
>   		size = 128;
> @@ -283,7 +314,7 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
>   		if (size > bar_fixed_size) {
>   			dev_err(&epf->dev,
>   				"requested BAR size is larger than fixed size\n");
> -			return NULL;
> +			return -EINVAL;
>   		}
>   		size = bar_fixed_size;
>   	} else {
> @@ -308,13 +339,25 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
>   	}
>   
>   	dev = epc->dev.parent;
> -	space = dma_alloc_coherent(dev, aligned_size, &phys_addr, GFP_KERNEL);
> -	if (!space) {
> -		dev_err(dev, "failed to allocate mem space\n");
> -		return NULL;
> +
> +	if (from_memory) {
> +		space = dma_alloc_coherent(dev, aligned_size,
> +					   &phys_addr, GFP_KERNEL);
> +		if (!space) {
> +			dev_err(dev, "failed to allocate mem space\n");
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	epf_bar[bar].phys_addr = from_memory ?
> +			phys_addr : ALIGN_DOWN(inbound_addr, aligned_size);
> +
> +	if (!from_memory && (epf_bar[bar].phys_addr + size < up)) {
> +		dev_err(&epf->dev,
> +			"Given bar can't fit required inbound memory region\n");

consider bar -> BAR

> +		return -EINVAL;
>   	}
>   


Thanks,
Alok