linux-kernel - Re: [PATCH v1 01/10] PCI/P2PDMA: Remove redundant bus

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Message-ID: <20250806145825.2654ee59.alex.williamson@redhat.com>
Date: Wed, 6 Aug 2025 14:58:25 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Leon Romanovsky <leonro@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Christian König
 <christian.koenig@....com>, Christoph Hellwig <hch@....de>,
 dri-devel@...ts.freedesktop.org, iommu@...ts.linux.dev, Jens Axboe
 <axboe@...nel.dk>, Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-mm@...ck.org, linux-pci@...r.kernel.org, Logan Gunthorpe
 <logang@...tatee.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Robin
 Murphy <robin.murphy@....com>, Sumit Semwal <sumit.semwal@...aro.org>,
 Vivek Kasireddy <vivek.kasireddy@...el.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v1 01/10] PCI/P2PDMA: Remove redundant bus_offset from
 map state

On Mon,  4 Aug 2025 16:00:36 +0300
Leon Romanovsky <leon@...nel.org> wrote:

> From: Leon Romanovsky <leonro@...dia.com>
> 
> Remove the bus_off field from pci_p2pdma_map_state since it duplicates
> information already available in the pgmap structure. The bus_offset
> is only used in one location (pci_p2pdma_bus_addr_map) and is always
> identical to pgmap->bus_offset.
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  drivers/pci/p2pdma.c       | 1 -
>  include/linux/pci-p2pdma.h | 3 +--
>  2 files changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index da5657a020074..274bb7bcc0bc5 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -1009,7 +1009,6 @@ void __pci_p2pdma_update_state(struct pci_p2pdma_map_state *state,
>  {
>  	state->pgmap = page_pgmap(page);
>  	state->map = pci_p2pdma_map_type(state->pgmap, dev);
> -	state->bus_off = to_p2p_pgmap(state->pgmap)->bus_offset;
>  }
>  
>  /**
> diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
> index 075c20b161d98..b502fc8b49bf9 100644
> --- a/include/linux/pci-p2pdma.h
> +++ b/include/linux/pci-p2pdma.h
> @@ -146,7 +146,6 @@ enum pci_p2pdma_map_type {
>  struct pci_p2pdma_map_state {
>  	struct dev_pagemap *pgmap;
>  	enum pci_p2pdma_map_type map;
> -	u64 bus_off;
>  };
>  
>  /* helper for pci_p2pdma_state(), do not use directly */
> @@ -186,7 +185,7 @@ static inline dma_addr_t
>  pci_p2pdma_bus_addr_map(struct pci_p2pdma_map_state *state, phys_addr_t paddr)
>  {
>  	WARN_ON_ONCE(state->map != PCI_P2PDMA_MAP_BUS_ADDR);
> -	return paddr + state->bus_off;
> +	return paddr + to_p2p_pgmap(state->pgmap)->bus_offsetf;
>  }
>  
>  #endif /* _LINUX_PCI_P2P_H */

Looks like you're relying on this bogus code getting resolved in the
next patch...

In file included from kernel/dma/direct.c:16:
./include/linux/pci-p2pdma.h: In function ‘pci_p2pdma_bus_addr_map’:
./include/linux/pci-p2pdma.h:188:24: error: implicit declaration of function ‘to_p2p_pgmap’ [-Wimplicit-function-declaration]
  188 |         return paddr + to_p2p_pgmap(state->pgmap)->bus_offsetf;
      |                        ^~~~~~~~~~~~
./include/linux/pci-p2pdma.h:188:50: error: invalid type argument of ‘->’ (have ‘int’)
  188 |         return paddr + to_p2p_pgmap(state->pgmap)->bus_offsetf;
      |                                                  ^~
./include/linux/pci-p2pdma.h:189:1: error: control reaches end of non-void function [-Werror=return-type]
  189 | }
      | ^

to_p2p_pgmap() is a static function and struct pci_p2pdma_pagemap
doesn't have a bus_offsetf member.  Thanks,

Alex