linux-kernel - Re: [PATCH v3 0/8] PCI: Align small BARs

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Message-Id: <877b71ea-341b-4013-bbee-8f4df9c961c9@app.fastmail.com>
Date: Wed, 07 Aug 2024 17:42:03 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Stewart Hildebrand" <stewart.hildebrand@....com>,
 "Bjorn Helgaas" <bhelgaas@...gle.com>,
 "Thomas Gleixner" <tglx@...utronix.de>, "Ingo Molnar" <mingo@...hat.com>,
 "Borislav Petkov" <bp@...en8.de>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, "Michael Ellerman" <mpe@...erman.id.au>,
 "Nicholas Piggin" <npiggin@...il.com>,
 "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "Sam Ravnborg" <sam@...nborg.org>,
 "Yongji Xie" <elohimes@...il.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 "Philipp Stanner" <pstanner@...hat.com>
Cc: x86@...nel.org, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 0/8] PCI: Align small BARs

On Wed, Aug 7, 2024, at 17:17, Stewart Hildebrand wrote:
> In this context, "small" is defined as max(SZ_4K, PAGE_SIZE).
>
> This series sets the default minimum resource alignment to
> max(SZ_4K, PAGE_SIZE) for memory BARs. In preparation, it makes an
> optimization and addresses some corner cases observed when reallocating
> BARs. I consider the prepapatory patches to be prerequisites to changing
> the default BAR alignment.

It's probably worth noting that Linux does not support any
architectures with software page sizes smaller than 4KB,
and it would likely break a lot of assumptions, so
max(SZ_4K, PAGE_SIZE) is really the same as PAGE_SIZE
in practice.

     Arnd