linux-kernel - Re: [PATCH v6 03/16] dma-debug: refactor to use physical addresses for page mapping

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Message-ID: <20250910052618.GH341237@unreal>
Date: Wed, 10 Sep 2025 08:26:18 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Jason Gunthorpe <jgg@...dia.com>,
	Abdiel Janulgue <abdiel.janulgue@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>, Danilo Krummrich <dakr@...nel.org>,
	David Hildenbrand <david@...hat.com>, iommu@...ts.linux.dev,
	Jason Wang <jasowang@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	Joerg Roedel <joro@...tes.org>, Jonathan Corbet <corbet@....net>,
	Juergen Gross <jgross@...e.com>, kasan-dev@...glegroups.com,
	Keith Busch <kbusch@...nel.org>, linux-block@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-nvme@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-trace-kernel@...r.kernel.org,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Robin Murphy <robin.murphy@....com>, rust-for-linux@...r.kernel.org,
	Sagi Grimberg <sagi@...mberg.me>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	virtualization@...ts.linux.dev, Will Deacon <will@...nel.org>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v6 03/16] dma-debug: refactor to use physical addresses
 for page mapping

On Tue, Sep 09, 2025 at 10:37:48PM +0300, Leon Romanovsky wrote:
> On Tue, Sep 09, 2025 at 04:27:31PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> 
> <...>
> 
> >  include/linux/page-flags.h         |  1 +
> 
> <...>
> 
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -614,6 +614,7 @@ FOLIO_FLAG(dropbehind, FOLIO_HEAD_PAGE)
> >   * available at this point.
> >   */
> >  #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
> > +#define PhysHighMem(__p) (PageHighMem(phys_to_page(__p)))
> 
> This was a not so great idea to add PhysHighMem() because of "else"
> below which unfolds to maze of macros and automatically generated
> functions with "static inline int Page##uname ..." signature.
> 
> >  #define folio_test_highmem(__f)	is_highmem_idx(folio_zonenum(__f))
> >  #else
> >  PAGEFLAG_FALSE(HighMem, highmem)

After sleeping over it, the following hunk will help:

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index dfbc4ba86bba2..2a1f346178024 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -614,11 +614,11 @@ FOLIO_FLAG(dropbehind, FOLIO_HEAD_PAGE)
  * available at this point.
  */
 #define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
-#define PhysHighMem(__p) (PageHighMem(phys_to_page(__p)))
 #define folio_test_highmem(__f)        is_highmem_idx(folio_zonenum(__f))
 #else
 PAGEFLAG_FALSE(HighMem, highmem)
 #endif
+#define PhysHighMem(__p) (PageHighMem(phys_to_page(__p)))

 /* Does kmap_local_folio() only allow access to one page of the folio? */
 #ifdef CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP


> 
> Thanks
>