Messages in this thread | | | From | "Kroening, Gary" <> | Subject | RE: [PATCH 1/1] x86/platform/x86: Fix count of CHas on multi-pci-segment arches | Date | Tue, 13 Mar 2018 05:06:59 +0000 |
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Thanks, Kan -- your patch looks good, and cleaner than the previous method!
Tonight, I've tested it on our in-house simulator for the following configurations. The simulator has been matching hardware well for this issue -- we'll do more testing on real hardware, but I'm confident you have it right.
Terminology:
"hubless" -- equivalent to "glueless" or "white box" where our BIOS sets things up with a single bus for all sockets.
"scalable" -- BIOS assigns a new segment/domain for each socket
Configurations tested so far: - single-socket hubless/scalable - two sockets, scalable - four sockets, hubless - eight sockets, scalable
In all cases, skx_count_chabox() is returning 28 for Skylake server. Thanks for the quick response! Gary
> -----Original Message----- > From: Liang, Kan [mailto:kan.liang@linux.intel.com] > Sent: Monday, March 12, 2018 8:43 PM > To: Kroening, Gary; mingo@redhat.com; hpa@zytor.com; tglx@linutronix.de; > peterz@infradead.org > Cc: Travis, Mike; Banman, Andrew; Sivanich, Dimitri; Anderson, Russ; > x86@kernel.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH 1/1] x86/platform/x86: Fix count of CHas on multi-pci- > segment arches > > > > On 3/7/2018 3:33 PM, Kroening, Gary wrote: > > For systems with a single PCI segment, it is sufficient to look for the > > bus number to change in order to determine that all of the CHa's have > > been counted for a single socket. > > > > However, for multi PCI segment systems, each socket is given a new > > segment and the bus number does NOT change. So looking only for the > > bus number to change ends up counting all of the CHa's on all sockets > > in the system. This leads to writing CPU MSRs beyond a valid range and > > causes an error in ivbep_uncore_msr_init_box(). > > > > The fix is to check for either the bus number or segment number to > change. > > > > Hi Gary, > > There is a recommended way in uncore document to query the number of > CHAs on Skylake server. > I have a patch to implement the new way. > > Could you please take a look at the patch and see if it can fix your > issue? > > > Thanks, > Kan > > ------ > From 55f54b2fa3021c691c2fd4f5cfc8f441fd104e91 Mon Sep 17 00:00:00 2001 > From: Kan Liang <kan.liang@linux.intel.com> > Date: Mon, 12 Mar 2018 13:03:40 -0700 > Subject: [PATCH] perf/x86/intel/uncore: Querying number of CHAs from > CAPID6 register > > The number of CHAs is miscalculated on multi PCI domain systems on > Skylake server > > (From Kroening, Gary: > > For systems with a single PCI segment, it is sufficient to look for the > bus number to change in order to determine that all of the CHa's have > been counted for a single socket. > However, for multi PCI segment systems, each socket is given a new > segment and the bus number does NOT change. So looking only for the > bus number to change ends up counting all of the CHa's on all sockets > in the system. This leads to writing CPU MSRs beyond a valid range and > causes an error in ivbep_uncore_msr_init_box().) > > To determine the number of CHAs, it should read bits 27:0 in the CAPID6 > register located at Device 30, Function 3, Offset 0x9C. These 28 bits > form a bit vector of available LLC slices and the CHAs that manage those > slices. > > Fixes: cd34cd97b7b4 ("perf/x86/intel/uncore: Add Skylake server uncore > support") > Reported-by: Kroening, Gary <gary.kroening@hpe.com> > Signed-off-by: Kan Liang <kan.liang@linux.intel.com> > --- > arch/x86/events/intel/uncore_snbep.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) > > diff --git a/arch/x86/events/intel/uncore_snbep.c > b/arch/x86/events/intel/uncore_snbep.c > index d4672ed..a42715b 100644 > --- a/arch/x86/events/intel/uncore_snbep.c > +++ b/arch/x86/events/intel/uncore_snbep.c > @@ -3575,24 +3575,20 @@ static struct intel_uncore_type > *skx_msr_uncores[] = { > NULL, > }; > > +#define SKX_CAPID6 0x9c > +#define SKX_CHA_BIT_WIDTH 28 > + > static int skx_count_chabox(void) > { > - struct pci_dev *chabox_dev = NULL; > - int bus, count = 0; > + struct pci_dev *dev = NULL; > + u32 val = 0; > > - while (1) { > - chabox_dev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x208d, > chabox_dev); > - if (!chabox_dev) > - break; > - if (count == 0) > - bus = chabox_dev->bus->number; > - if (bus != chabox_dev->bus->number) > - break; > - count++; > - } > + dev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x2083, dev); > + if (!dev) > + return 0; > > - pci_dev_put(chabox_dev); > - return count; > + pci_read_config_dword(dev, SKX_CAPID6, &val); > + return bitmap_weight((unsigned long *)&val, SKX_CHA_BIT_WIDTH); > } > > void skx_uncore_cpu_init(void) > -- > 2.7.4
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