linux-kernel - Re: PCI PM: Restore standard config registers of all devices early

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.2.00.0902030742530.3247@localhost.localdomain>
Date:	Tue, 3 Feb 2009 07:48:20 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Andreas Schwab <schwab@...e.de>, Len Brown <lenb@...nel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: PCI PM: Restore standard config registers of all devices early



On Tue, 3 Feb 2009, Benjamin Herrenschmidt wrote:
> 
> Now where it gets funny is that I've added code to read the BAR and
> command register content before, between, and after those calls and
> print it and .. they are sane... Until i discovered that what happens is
> that the new generic code seems to actually blast 0 all over my config
> space if I don't call pci_save_state() in suspend(). I suppose I was
> missing a "mandatory" call here... but the core should be more robust,
> ie it shouldn't erase the config space of something because a driver
> "forgot" to call pci_save_state() !

You've found a bug somewhere.

We _should_ be saving things, the legacy code does something like this:

        if (drv && drv->suspend) {
                pci_dev->state_saved = false;

                i = drv->suspend(pci_dev, state);
                suspend_report_result(drv->suspend, i);
                if (i)
                        return i;

                if (pci_dev->state_saved)
                        goto Fixup;

                if (WARN_ON_ONCE(pci_dev->current_state != PCI_D0))
                        goto Fixup;
        }

        pci_save_state(pci_dev);

ie if your ->suspend function doesn't use pci_save_state() itself (which 
sets that "state_saved" flag to true), then the generic code will do it 
for you.

Also, on the resume path, we actually have

        if (pci_dev->state_saved)
                pci_restore_standard_config(pci_dev);

so I wonder how the heck you got that blast of all zeroes - because we 
clearly shouldn't be trying to restore any unsaved state!

So if you can figure out how it does all that...

		Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/