linux-kernel - RE: [RFC PATCH v3 08/10] EDAC/amd64: Gather hardware information early

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Message-ID: <SN6PR12MB26393DDA0F1818DCDD2D7953F8BA0@SN6PR12MB2639.namprd12.prod.outlook.com>
Date:   Fri, 6 Sep 2019 19:14:57 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v3 08/10] EDAC/amd64: Gather hardware information
 early

> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org <linux-kernel-owner@...r.kernel.org> On Behalf Of Borislav Petkov
> Sent: Thursday, August 29, 2019 4:23 AM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>
> Cc: linux-edac@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [RFC PATCH v3 08/10] EDAC/amd64: Gather hardware information early
> 
> On Thu, Aug 22, 2019 at 12:00:02AM +0000, Ghannam, Yazen wrote:
> > From: Yazen Ghannam <yazen.ghannam@....com>
> >
> > Split out gathering hardware information from init_one_instance() into a
> > separate function get_hardware_info().
> >
> > This is necessary so that the information can be cached earlier and used
> > to check if memory is populated and if ECC is enabled on a node.
> >
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> > ---
> >  drivers/edac/amd64_edac.c | 76 +++++++++++++++++++++++----------------
> >  1 file changed, 45 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
> > index 4d1e6daa7ec4..84832771dec0 100644
> > --- a/drivers/edac/amd64_edac.c
> > +++ b/drivers/edac/amd64_edac.c
> > @@ -3405,34 +3405,17 @@ static void compute_num_umcs(void)
> >  	edac_dbg(1, "Number of UMCs: %x", num_umcs);
> >  }
> >
> > -static int init_one_instance(unsigned int nid)
> > +static int get_hardware_info(struct amd64_pvt *pvt,
> > +			     struct amd64_family_type *fam_type)
> >  {
> > -	struct pci_dev *F3 = node_to_amd_nb(nid)->misc;
> > -	struct amd64_family_type *fam_type = NULL;
> > -	struct mem_ctl_info *mci = NULL;
> > -	struct edac_mc_layer layers[2];
> > -	struct amd64_pvt *pvt = NULL;
> >  	u16 pci_id1, pci_id2;
> > -	int err = 0, ret;
> > -
> > -	ret = -ENOMEM;
> > -	pvt = kzalloc(sizeof(struct amd64_pvt), GFP_KERNEL);
> > -	if (!pvt)
> > -		goto err_ret;
> > -
> > -	pvt->mc_node_id	= nid;
> > -	pvt->F3 = F3;
> > -
> > -	ret = -EINVAL;
> > -	fam_type = per_family_init(pvt);
> > -	if (!fam_type)
> > -		goto err_free;
> > +	int ret = -EINVAL;
> >
> >  	if (pvt->fam >= 0x17) {
> >  		pvt->umc = kcalloc(num_umcs, sizeof(struct amd64_umc), GFP_KERNEL);
> 
> Yeah, a get_hardware_info() function which does an allocation of that
> struct amd64_umc on => F17 which is only 20 bytes. Just add it into the
> pvt struct:
> 
> struct amd64_pvt {
> 	...
> 	struct amd64_umc umc;  /* UMC registers */
> };
> 
> and be done with it. This should simplify the code flow here a bit and
> 20 bytes more per pvt is not a big deal.
> 

This struct is used per channel, so we may have 2-8 per system. We could fix it at the max (8).
What do you think?

Thanks,
Yazen