Messages in this thread | | | Subject | Re: [PATCH v5 2/9] watchdog/hpwdt: Remove legacy NMI sourcing. | From | Guenter Roeck <> | Date | Mon, 26 Feb 2018 17:29:55 -0800 |
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On 02/26/2018 05:02 PM, Jerry Hoemann wrote: > On Mon, Feb 26, 2018 at 06:32:30AM -0800, Guenter Roeck wrote: >> On 02/26/2018 06:11 AM, Arnd Bergmann wrote: >>> On Mon, Feb 26, 2018 at 4:22 AM, Jerry Hoemann <jerry.hoemann@hpe.com> wrote: >>>> Gen8 and prior Proliant systems supported the "CRU" interface >>>> to firmware. This interfaces allows linux to "call back" into firmware >>>> to source the cause of an NMI. This feature isn't fully utilized >>>> as the actual source of the NMI isn't printed, the driver only >>>> indicates that the source couldn't be determined when the call >>>> fails. >>>> >>>> With the advent of Gen9, iCRU replaces the CRU. The call back >>>> feature is no longer available in firmware. To be compatible and >>>> not attempt to call back into firmware on system not supporting CRU, >>>> the SMBIOS table is consulted to determine if it is safe to >>>> make the call back or not. >>>> >>>> This results in about half of the driver code being devoted >>>> to either making CRU calls or determing if it is safe to make >>>> CRU calls. As noted, the driver isn't really using the results of >>>> the CRU calls. >>>> >>>> Furthermore, as a consequence of the Spectre security issue, the >>>> BIOS/EFI calls are being wrapped into Spectre-disabling section. >>>> Removing the call back in hpwdt_pretimeout assists in this effort. >>>> >>>> As the CRU sourcing of the NMI isn't required for handling the >>>> NMI and there are security concerns with making the call back, remove >>>> the legacy (pre Gen9) NMI sourcing and the DMI code to determine if >>>> the system had the CRU interface. >>>> >>>> Signed-off-by: Jerry Hoemann <jerry.hoemann@hpe.com> >>> >>> This avoids a warning in mainline kernels, so that's great: >>> >>> drivers/watchdog/hpwdt.o: warning: objtool: .text+0x24: indirect call >>> found in RETPOLINE build >>> >>> I wonder what we do about stable kernels. Are both this patch and the patch >>> that added the objtool warning message candidates for backports to >>> stable kernels? >>> >> >> Makes sense to me, but it is really a bit more than a bug fix, so I'll >> leave it up to Jerry/HPE to make the call in respect to hpwdt. >> > > Generally speaking, HPE customers who run linux do so through a distro > vendor and pick up patches from them. But I'm sure there are some > customers who do things differently. > > The distro vendor's have their own repos and we'll work with them > to back port patches to their code base. So, I typically don't do a lot > of kernel.org stable branch work. > > Looks like objtool has been enhanced to find Spectre vulnerable code. > Are the other kernel patches related to Spectre being back ported > to stable release lines? If yes, it probably make sense to do > the hpwdt change as well. >
Spectre has been backported to v4.4 and later. I don't know about earlier kernels.
> Is just the patch removing the firmware call back wanted/needed? Or the > whole driver rewrite? (The older baseline don't have all the watchdog > features that the patch set uses.) >
We would only want to backport this patch. The rest is really out of scope.
> Which stable baseline(s) would need to be patched? Priority? > > Who does it? (i.e. do you want me to submit patches to the stable baseline?) > We would tag the patch for stable (and submit it into v4.16-rc). Greg would take care of the rest unless there are conflicts, in which case we get a note telling us that a backport is needed.
Guenter
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