linux-kernel - Re: [PATCH v2 2/5] x86/PCI: Support additional MMIO range capabilities

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Date:	Mon, 28 Apr 2014 22:04:34 -0500
From:	Suravee Suthikulanit <suravee.suthikulpanit@....com>
To:	Myron Stowe <myron.stowe@...il.com>, Borislav Petkov <bp@...e.de>
CC:	Myron Stowe <myron.stowe@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci <linux-pci@...r.kernel.org>,
	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>,
	<kim.naru@....com>, <daniel@...ascale.com>,
	Thomas Gleixner <tglx@...utronix.de>, <mingo@...hat.com>,
	<hpa@...or.com>, x86 <x86@...nel.org>, <sp@...ascale.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] x86/PCI: Support additional MMIO range capabilities

On 4/25/2014 5:24 PM, Myron Stowe wrote:
> On Sun, Apr 20, 2014 at 1:59 AM, Borislav Petkov <bp@...e.de> wrote:
>> Drop Andreas' old email address from CC as it keeps bouncing.
>>
>> On Sat, Apr 19, 2014 at 03:52:20PM +0200, Borislav Petkov wrote:
>>>> -static void __init pci_enable_pci_io_ecs(void)
>>>> +static void __init pci_enable_pci_io_ecs(u8 bus, u8 slot)
>>>>   {
>>>>   #ifdef CONFIG_AMD_NB
>>>>      unsigned int i, n;
>>>> +   u8 limit;
>>>>
>>>>      for (n = i = 0; !n && amd_nb_bus_dev_ranges[i].dev_limit; ++i) {
>>>> -           u8 bus = amd_nb_bus_dev_ranges[i].bus;
>>>> -           u8 slot = amd_nb_bus_dev_ranges[i].dev_base;
>>>> -           u8 limit = amd_nb_bus_dev_ranges[i].dev_limit;
>>>> +           /* Try matching for the bus range */
>>>> +           if ((bus != amd_nb_bus_dev_ranges[i].bus) ||
>>>> +               (slot != amd_nb_bus_dev_ranges[i].dev_base))
>>>> +                   continue;
>>>> +
>>>> +           limit = amd_nb_bus_dev_ranges[i].dev_limit;
>>>>
>>>> +           /* Setup all northbridges within the range */
>>>>              for (; slot < limit; ++slot) {
>>>>                      u32 val = read_pci_config(bus, slot, 3, 0);
>>>> -
>>>> -                   if (!early_is_amd_nb(val))
>>>> +                   if (!val)
>>>>                              continue;
>>>>
>>>>                      val = read_pci_config(bus, slot, 3, 0x8c);
>>>> @@ -375,13 +457,14 @@ static void __init pci_enable_pci_io_ecs(void)
>>>>                              val |= ENABLE_CF8_EXT_CFG >> 32;
>>>
>>> What a fun shifting!
>>>
>>> Maybe you should do
>>>
>>> #define ENABLE_CF8_EXT_CFG    BIT(46 - 32)
>>>
>>> to show exactly what you mean and how the bit is defined in MSR NB_CFG1
>>> and also show how the high 32-bits are mapped into F3x8c, while at it.
>>>
>>> And then you can drop the shifting at the call site.
>>
>> Ok, I see another fun with this ECS enabling:
>>
>> There's a enable_pci_io_ecs() which enables ECS through the NB_CFG MSR
>> which is called as part of the notifier *and* there's a PCI write to
>> that same bit in pci_enable_pci_io_ecs() which iterates over all NBs.
>>
>> So, AFAICT, we do it twice and the second time is not needed. Which
>> means, you probably can drop pci_enable_pci_io_ecs() completely and use
>> solely the notifier?
>
> It does look as if there is some duplication with respect to setting
> MSR_AMD64_NB_CFG's (which is aliased at D18F3x8c [1])
> ENABLE_CF8_EXT_CFG enable bit but there are at least a couple of
> differences.
>
> enable_pci_io_ecs() only sets the bit on one NB whereas
> pci_enable_pci_io_ecs iterates over all the NBs (as you mentioned
> above).  The other difference has something to do with Xen; see the
> origin of pci_enable_pci_io_ecs - commit 24d9b70b8.
>
>>
>> Yes, no?
>
> Suravee, Kim - either of you want to chime in here?

I believe the notifier is mainly for the cores which are initially 
offline, and then brought up online afterward.

Suravee

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