Messages in this thread | | | Subject | Re: [PATCH v5 2/9] watchdog/hpwdt: Remove legacy NMI sourcing. | From | Guenter Roeck <> | Date | Mon, 26 Feb 2018 06:32:30 -0800 |
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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.
Guenter
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