LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
From: Leonardo Bras <leonardo@linux.ibm.com>
To: desnesn@linux.ibm.com, linuxppc-dev@lists.ozlabs.org
Cc: desnesn@linux.ibm.com, gromero@linux.ibm.com
Subject: Re: [PATCH] powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
Date: Sat, 15 Feb 2020 02:39:17 -0300
Message-ID: <9ba1d74b53b573d62becba084bb796d3e983f9b4.camel@linux.ibm.com> (raw)

[-- Attachment #1: Type: text/plain, Size: 1475 bytes --]

Hello Desnes, thanks for the patch.

"Desnes A. Nunes do Rosario" <desnesn@linux.ibm.com> writes:

> PowerVM systems running compatibility mode on a few Power8 revisions are
> still vulnerable to the hardware defect that loses PMU exceptions arriving
> prior to a context switch.
>
> The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG
> cpu_feature bit, nevertheless this bit also needs to be set for PowerVM
> compatibility mode systems.
>
> Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG")
> Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com>
> ---
>  arch/powerpc/kernel/cputable.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
> index e745abc5457a..5bfef6263dfb 100644
> --- a/arch/powerpc/kernel/cputable.c
> +++ b/arch/powerpc/kernel/cputable.c
> @@ -2198,6 +2198,8 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
>  		if (old.oprofile_cpu_type != NULL) {
>  			t->oprofile_cpu_type = old.oprofile_cpu_type;
>  			t->oprofile_type = old.oprofile_type;
> +			if (old.cpu_features & CPU_FTR_PMAO_BUG)
> +				t->cpu_features |= CPU_FTR_PMAO_BUG;

What are your thoughts about doing:
	t->cpu_features |=  old.cpu_features & CPU_FTR_PMAO_BUG;

Also, I would recommend adding a short comment on top of the added
lines explaining why it is needed. 

Best regards,
Leonardo Bras


[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-15  5:39 Leonardo Bras [this message]
  -- strict thread matches above, loose matches on Subject: below --
2020-02-14  0:19 Desnes A. Nunes do Rosario
2020-02-15  6:26 ` Leonardo Bras

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9ba1d74b53b573d62becba084bb796d3e983f9b4.camel@linux.ibm.com \
    --to=leonardo@linux.ibm.com \
    --cc=desnesn@linux.ibm.com \
    --cc=gromero@linux.ibm.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git