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From: Johannes Berg <johannes@sipsolutions.net>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>,
	dmaengine@vger.kernel.org,
	Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH] dmaengine: ioat: depends on !UML
Date: Mon, 09 Aug 2021 19:26:57 +0200	[thread overview]
Message-ID: <0ef27e7c8df520ca48900140b3930af279cd2466.camel@sipsolutions.net> (raw)
In-Reply-To: <CAPcyv4i0p-DaPA7YTid4XsUJUpq+L-c1kDNArb=0XXnFkXz-iw@mail.gmail.com>

On Mon, 2021-08-09 at 10:24 -0700, Dan Williams wrote:
> On Mon, Aug 9, 2021 at 2:25 AM Johannes Berg <johannes@sipsolutions.net> wrote:
> > 
> > From: Johannes Berg <johannes.berg@intel.com>
> > 
> > Now that UML has PCI support, this driver must depend also on
> > !UML since it pokes at X86_64 architecture internals that don't
> > exist on ARCH=um.
> > 
> 
> Do you really need to disable compilation of the whole driver just
> because an arch level helper does not exist on UML builds? Isn't there
> already a check for enqcmds on x86_64 to make sure the CPU is
> sufficiently feature enabled?

Hmm?

The problem here is that cpuid_eax() and cpuid_ebx() don't even exist on
UML, and that's not really surprising - ARCH=um is after all compiled to
run as a userspace process, not to run on bare metal. I guess
technically we could provide (fake or even sort of real) implementations
of these, but there's very little point?

I don't see why you would ever possibly want to have this driver
compiled on ARCH=um, even if it's compiled for x86-64 "subarch", since
there will be no such device to run against?

johannes


  reply	other threads:[~2021-08-09 17:27 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09  9:24 Johannes Berg
2021-08-09 16:02 ` Dave Jiang
2021-08-09 17:24 ` Dan Williams
2021-08-09 17:26   ` Johannes Berg [this message]
2021-08-25 13:31     ` Dan Williams
2021-08-25 13:33       ` Johannes Berg
2021-08-25 13:36         ` Dan Williams
2021-08-25 13:41           ` Johannes Berg
2021-08-25 13:53             ` Dan Williams
2021-08-25 11:31 ` Vinod Koul

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