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

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Message-ID: <20250902110651.GF10073@unreal>
Date: Tue, 2 Sep 2025 14:06:51 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: 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 Wed, Aug 06, 2025 at 02:58:25PM -0600, Alex Williamson wrote:
> 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 */

Sorry for long time to reply, I waited to see what is going on with DMA
phys_vec basic series and together with my summer vacation, it took a
while.

> 
> 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,

You are right, probably the best way to fix the error is simply squash
this change into the next patch.

Thanks



> 
> Alex
>