linux-kernel - Re: [PATCH] iommu/amd: Fix extended features logging

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Message-ID: <alpine.LNX.2.20.13.2104112326460.11104@monopod.intra.ispras.ru>
Date:   Sun, 11 Apr 2021 23:43:53 +0300 (MSK)
From:   Alexander Monakov <amonakov@...ras.ru>
To:     John Ogness <john.ogness@...utronix.de>
cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Joerg Roedel <jroedel@...e.de>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] iommu/amd: Fix extended features logging

On Sun, 11 Apr 2021, John Ogness wrote:

> > pr_info("") will also prepend 'AMD-Vi:' to the feature list, which is
> > nice.
> 
> I'd rather fix dev_info callers to allow pr_cont and then fix any code
> that is using this workaround.

Note that existing two users of pr_info("") that I found are not using that
as a workaround: efi.c is using that when it announced a list of EFI tables:

efi: ACPI=0xadffe000 ACPI 2.0=0xadffe014 TPMFinalLog=0xadf2d000 ESRT=0xab70d618 SMBIOS=0xab70b000 SMBIOS 3.0=0xab709000 RNG=0xab707b98 TPMEventLog=0x9602c018

and uvesafb.c similarly uses it to print a list of conditionally-present
strings. In both cases it is really a standalone message, not a continuation
for something previously printed.

In contrast, my patch deals with a continuation line. I wouldn't really like
the decoded feature list to appear on the same line as the previous message,
because it would end up quite long:

[    0.266332] pci 0000:00:00.2: AMD-Vi: Extended features (0x206d73ef22254ade):
[    0.266334] AMD-Vi:  PPR X2APIC NX GT IA GA PC GA_vAPIC

I think a good compromise is to change the first line from pci_info to pr_info,
losing the pci bus address. I'll send a v2.

Alexander