From: Liang, Kan > Sent: 27 May 2020 15:47 > On 5/27/2020 8:59 AM, David Laight wrote: > > From: kan.liang@xxxxxxxxxxxxxxx > >> Sent: 27 May 2020 13:31 > >> > >> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx> > >> > >> When counting IMC uncore events on some TGL machines, an oops will be > >> triggered. > >> [ 393.101262] BUG: unable to handle page fault for address: > >> ffffb45200e15858 > >> [ 393.101269] #PF: supervisor read access in kernel mode > >> [ 393.101271] #PF: error_code(0x0000) - not-present page > >> > >> Current perf uncore driver still use the IMC MAP SIZE inherited from > >> SNB, which is 0x6000. > >> However, the offset of IMC uncore counters for some TGL machines is > >> larger than 0x6000, e.g. 0xd8a0. > >> > >> Enlarge the IMC MAP SIZE for TGL to 0xe000. > > > > Replacing one 'random' constant with a different one > > doesn't seem like a proper fix. > > > > Surely the actual bounds of the 'memory' area are properly > > defined somewhere. > > Or at least should come from a table. > > > > You also need to verify that the offsets are within the mapped area. > > An unexpected offset shouldn't try to access an invalid address. > > Thanks for the review. > > I agree that we should add a check before mapping the area to prevent > the issue happens again. > > I think the check should be a generic check for all platforms which try > to map an area, not just for TGL. I will submit a separate patch for the > check. You need a check that the actual access is withing the mapped area. So instead of getting an OOPS you get a error. This is after you've mapped it. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
