From: Robert Richter <rric@kernel.org>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Suravee Suthikulanit <suravee.suthikulpanit@amd.com>,
Borislav Petkov <bp@alien8.de>,
Daniel J Blueman <daniel@numascale.com>,
Andreas Herrmann <herrmann.der.user@googlemail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Borislav Petkov <bp@suse.de>,
Myron Stowe <myron.stowe@redhat.com>
Subject: Re: [PATCH V5 3/4] x86/PCI: Stop enabling ECS for AMD CPUs after Fam16h
Date: Fri, 23 May 2014 17:05:18 +0200 [thread overview]
Message-ID: <20140523150518.GW27560@rric.localhost> (raw)
In-Reply-To: <CAErSpo5t+u+AYS5m6wo+AG7uXEkseUcmK9d-FF+SwpkcEWnkqA@mail.gmail.com>
On 23.05.14 07:01:41, Bjorn Helgaas wrote:
> [I guess I've been using the wrong term here. I think "ECS" just
> refers to the extended config space itself, and I should have been
> saying "IO ECS" or "EnableCf8ExtCfg".]
>
> My understanding was that if we don't enable IO ECS and we don't have
> MCFG, we will not be able to access extended config space. The system
> can certainly boot without extended config space, but some drivers may
> not work correctly, so it would be a regression from the user point of
> view.
No, I got you right. If we disable IO ECS there is no fallback if MCFG
fails... and this may cause a regression then.
I might be completely wrong here, but as I remember IO ECS only
affects access to cpu devices (bus 0, slot 0x18-0x1f). Thus, esp. PCIe
extended config space access works since a different host controller
handles this. So only cpu devices would see a regression and thus cpu
bringup code. I don't think ECS (either MCFG or IO ECS) is needed
anymore for cpu bringup (this is true for IBS, but I don't know of
other cpu features requiring ECS, though family 16h might introduced
new ones).
IMHO device drivers are not affected and wont get broken.
-Robert
next prev parent reply other threads:[~2014-05-23 15:05 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 16:44 [PATCH V4 0/4] x86/pci Fix numa_node info for AMD hostbridge and misc clean up suravee.suthikulpanit
2014-05-08 16:44 ` [PATCH V4 1/4] x86/PCI: Fix PCI root numa_node info on AMD family15h suravee.suthikulpanit
2014-05-08 16:44 ` [PATCH V4 2/4] x86/PCI: Clean up and mark early_root_info_init as deprecated suravee.suthikulpanit
2014-05-08 16:44 ` [PATCH V4 3/4] ACPI/PCI: Warn if we have to "guess" host bridge node information suravee.suthikulpanit
2014-05-08 16:44 ` [PATCH V4 4/4] X86/PCI: Remove unnecessary 'quirk_amd_nb_node' suravee.suthikulpanit
2014-05-14 5:54 ` [PATCH V4 0/4] x86/pci Fix numa_node info for AMD hostbridge and misc clean up Suravee Suthikulpanit
2014-05-14 13:11 ` Bjorn Helgaas
2014-05-21 23:17 ` [PATCH V5 " Bjorn Helgaas
2014-05-21 23:18 ` [PATCH V5 1/4] x86/PCI: Warn if we have to "guess" host bridge node information Bjorn Helgaas
2014-05-21 23:18 ` [PATCH V5 2/4] x86/PCI: Work around AMD Fam15h BIOSes that fail to provide _PXM Bjorn Helgaas
2014-05-21 23:18 ` [PATCH V5 3/4] x86/PCI: Stop enabling ECS for AMD CPUs after Fam16h Bjorn Helgaas
2014-05-21 23:38 ` Borislav Petkov
2014-05-22 17:56 ` Bjorn Helgaas
2014-05-22 19:17 ` Borislav Petkov
2014-05-22 20:20 ` Bjorn Helgaas
2014-05-22 21:00 ` Borislav Petkov
2014-05-22 23:39 ` Suravee Suthikulanit
2014-05-23 2:54 ` Bjorn Helgaas
2014-05-23 11:56 ` Robert Richter
2014-05-23 13:01 ` Bjorn Helgaas
2014-05-23 15:05 ` Robert Richter [this message]
2014-05-23 21:36 ` Suravee Suthikulanit
2014-05-24 0:31 ` Suravee Suthikulanit
2014-05-28 16:02 ` Bjorn Helgaas
2014-05-21 23:18 ` [PATCH V5 4/4] x86/PCI: Clean up and mark early_root_info_init() as deprecated Bjorn Helgaas
2014-05-23 0:43 ` [PATCH V5 0/4] x86/pci Fix numa_node info for AMD hostbridge and misc clean up Suravee Suthikulanit
2014-05-23 0:49 ` Suravee Suthikulanit
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