linux-kernel - Re: [PATCH] EDAC/amd64: remove unneeded call to reserve_mc_sibling

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Message-ID: <Y+q1mhrAKTobp3fa@yaz-fattaah>
Date:   Mon, 13 Feb 2023 22:11:38 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Tom Rix <trix@...hat.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Borislav Petkov <bp@...en8.de>, tony.luck@...el.com,
        james.morse@....com, mchehab@...nel.org, rric@...nel.org,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] EDAC/amd64: remove unneeded call to
 reserve_mc_sibling_devs()

On Mon, Feb 13, 2023 at 01:17:51PM -0800, Tom Rix wrote:
> 
> On 2/13/23 12:28 PM, Nathan Chancellor wrote:
> > On Mon, Feb 13, 2023 at 09:23:47PM +0100, Borislav Petkov wrote:
> > > On Mon, Feb 13, 2023 at 08:12:38PM +0000, Yazen Ghannam wrote:
> > > > These errors are encountered when extra warnings are enabled, correct?
> > > It says so in the warning which one it is: -Werror,-Wsometimes-uninitialized
> > > 
> > > Don't know if we enable that one for clang with W= or Nathan adds
> > > additional switches.
> > -Wsometimes-uninitialized is part of clang's -Wall so it is on by
> > default in all builds, regardless of W=
> > 
> > -Werror comes from CONFIG_WERROR, which is enabled with allmodconfig.
> > 
> > > > I think the following patch would resolve this issue. This is part of a set
> > > > that isn't fully applied.
> > > > https://lore.kernel.org/linux-edac/20230127170419.1824692-12-yazen.ghannam@amd.com/
> > > > 
> > > > Boris,
> > > > Do you think one of these patches should be applied or just hold off until the
> > > > entire original set is applied?
> > > I still wanted to go through the rest but I'm not sure I'll have time
> > > for it before the merge window. So unless this is breaking some silly
> > > testing scenario, I'd say I'll leave things as they are.
> > This breaks allmodconfig with clang, so it would be great if one of
> > these solutions was applied in the meantime.
> 
> This happens at least on allyesconfig clang W=1,2, i do not know about
> default, it's in a bad state as well.
>

Yes, this breaks on a default clang build. I just used "make LLVM=1" with the
same config I used before, and I see the error.

GCC doesn't seem to have a comparable warning to "-Wsometimes-uninitialized".
I went back and tried W=123 and no warnings in this code.

Building with clang was straightforward, so I'll try to include it in my
workflow in the future.

> It would be great if the clang build was working.
> 
> Nathan's patch is fine, go with that.
>

I agree Nathan's patch is fine, but would you all be okay with a simpler
change? Initializing the variables (as below) will silence the warnings, and
we know this is a false positive. Eventually this function will be reworked,
so a trivial workaround seems okay. What do y'all think?

Thanks,
Yazen

------

diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index 1c4bef1cdf28..5b42533f306a 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -3928,7 +3928,7 @@ static const struct attribute_group
*amd64_edac_attr_groups[] = {

 static int hw_info_get(struct amd64_pvt *pvt)
  {
  -       u16 pci_id1, pci_id2;
  +       u16 pci_id1 = 0, pci_id2 = 0;
          int ret;

	          if (pvt->fam >= 0x17) {

------