Re: [PATCH 1/1] EDAC/i10nm: Skip the absent memory controllers

[Kai-Heng Feng]

On Thu, Jul 6, 2023 at 9:46 PM Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx> wrote:
>
> Some Sapphire Rapids workstations' absent memory controllers
> still appear as PCIe devices that fool the i10nm_edac driver
> and result in "shift exponet -66 is negative" call traces
> from skx_get_dimm_info().
>
> Skip the absent memory controllers to avoid the call traces.
>
> Reported-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-edac/CAAd53p41Ku1m1rapeqb1xtD+kKuk+BaUW=dumuoF0ZO3GhFjFA@xxxxxxxxxxxxxx/T/#m5de16dce60a8c836ec235868c7c16e3fefad0cc2
> Reported-by: Koba Ko <koba.ko@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-edac/SA1PR11MB71305B71CCCC3D9305835202892AA@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/T/#t
> Fixes: d4dc89d069aa ("EDAC, i10nm: Add a driver for Intel 10nm server processors")
> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>

Tested-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>

> ---
>  drivers/edac/i10nm_base.c | 54 +++++++++++++++++++++++++++++++++++----
>  1 file changed, 49 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/edac/i10nm_base.c b/drivers/edac/i10nm_base.c
> index a897b6aff368..349ff6cfb379 100644
> --- a/drivers/edac/i10nm_base.c
> +++ b/drivers/edac/i10nm_base.c
> @@ -658,13 +658,49 @@ static struct pci_dev *get_ddr_munit(struct skx_dev *d, int i, u32 *offset, unsi
>         return mdev;
>  }
>
> +/**
> + * i10nm_imc_absent() - Check whether the memory controller @imc is absent
> + *
> + * @imc    : The pointer to the structure of memory controller EDAC device.
> + *
> + * RETURNS : true if the memory controller EDAC device is absent, false otherwise.
> + */
> +static bool i10nm_imc_absent(struct skx_imc *imc)
> +{
> +       u32 mcmtr;
> +       int i;
> +
> +       switch (res_cfg->type) {
> +       case SPR:
> +               for (i = 0; i < res_cfg->ddr_chan_num; i++) {
> +                       mcmtr = I10NM_GET_MCMTR(imc, i);
> +                       edac_dbg(1, "ch%d mcmtr reg %x\n", i, mcmtr);
> +                       if (mcmtr != ~0)
> +                               return false;
> +               }
> +
> +               /*
> +                * Some workstations' absent memory controllers still
> +                * appear as PCIe devices, misleading the EDAC driver.
> +                * By observing that the MMIO registers of these absent
> +                * memory controllers consistently hold the value of ~0.
> +                *
> +                * We identify a memory controller as absent by checking
> +                * if its MMIO register "mcmtr" == ~0 in all its channels.
> +                */
> +               return true;
> +       default:
> +               return false;
> +       }
> +}
> +
>  static int i10nm_get_ddr_munits(void)
>  {
>         struct pci_dev *mdev;
>         void __iomem *mbase;
>         unsigned long size;
>         struct skx_dev *d;
> -       int i, j = 0;
> +       int i, lmc, j = 0;
>         u32 reg, off;
>         u64 base;
>
> @@ -690,7 +726,7 @@ static int i10nm_get_ddr_munits(void)
>                 edac_dbg(2, "socket%d mmio base 0x%llx (reg 0x%x)\n",
>                          j++, base, reg);
>
> -               for (i = 0; i < res_cfg->ddr_imc_num; i++) {
> +               for (lmc = 0, i = 0; i < res_cfg->ddr_imc_num; i++) {
>                         mdev = get_ddr_munit(d, i, &off, &size);
>
>                         if (i == 0 && !mdev) {
> @@ -700,8 +736,6 @@ static int i10nm_get_ddr_munits(void)
>                         if (!mdev)
>                                 continue;
>
> -                       d->imc[i].mdev = mdev;
> -
>                         edac_dbg(2, "mc%d mmio base 0x%llx size 0x%lx (reg 0x%x)\n",
>                                  i, base + off, size, reg);
>
> @@ -712,7 +746,17 @@ static int i10nm_get_ddr_munits(void)
>                                 return -ENODEV;
>                         }
>
> -                       d->imc[i].mbase = mbase;
> +                       d->imc[lmc].mbase = mbase;
> +                       if (i10nm_imc_absent(&d->imc[lmc])) {
> +                               pci_dev_put(mdev);
> +                               iounmap(mbase);
> +                               d->imc[lmc].mbase = NULL;
> +                               edac_dbg(2, "Skip absent mc%d\n", i);
> +                               continue;
> +                       } else {
> +                               d->imc[lmc].mdev = mdev;
> +                               lmc++;
> +                       }
>                 }
>         }
>
> --
> 2.17.1
>