Messages in this thread | | | Subject | Re: [PATCH v8 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU | From | Gary R Hook <> | Date | Tue, 12 Jun 2018 13:37:43 -0500 |
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On 06/05/2018 12:06 PM, Greg KH wrote: > On Tue, Jun 05, 2018 at 11:58:13AM -0500, Gary R Hook wrote: >> On 05/29/2018 01:39 PM, Greg KH wrote: >>> On Tue, May 29, 2018 at 01:23:23PM -0500, Gary R Hook wrote: >>>> Implement a skeleton framework for debugfs support in the >>>> AMD IOMMU. Add a hidden boolean to Kconfig that is defined >>>> for the AMD IOMMU when general IOMMY DebugFS support is >>>> enabled. >>>> >>>> Signed-off-by: Gary R Hook <gary.hook@amd.com> >>>> --- >>>> drivers/iommu/Kconfig | 4 ++++ >>>> drivers/iommu/Makefile | 1 + >>>> drivers/iommu/amd_iommu_debugfs.c | 39 +++++++++++++++++++++++++++++++++++++ >>>> drivers/iommu/amd_iommu_init.c | 6 ++++-- >>>> drivers/iommu/amd_iommu_proto.h | 6 ++++++ >>>> drivers/iommu/amd_iommu_types.h | 5 +++++ >>>> 6 files changed, 59 insertions(+), 2 deletions(-) >>>> create mode 100644 drivers/iommu/amd_iommu_debugfs.c >>>> >>>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig >>>> index f9af25ac409f..ec223f6f4ad4 100644 >>>> --- a/drivers/iommu/Kconfig >>>> +++ b/drivers/iommu/Kconfig >>>> @@ -137,6 +137,10 @@ config AMD_IOMMU >>>> your BIOS for an option to enable it or if you have an IVRS ACPI >>>> table. >>>> +config AMD_IOMMU_DEBUGFS >>>> + def_bool y >>> >>> Why default y? Can you not boot a box without this? If not, it should >>> not be Y. >> >> Again, apologies for not seeing this sooner. >> >> Yes, the system can boot without this. The idea of a hidden option was >> surfaced by Robin, and after my first approach was shot down, I tried this. >> >> Logic: If the over-arching IOMMU debugfs option is enabled, then >> AMD_IOMMU_DEBUGFS gets defined, and AMD IOMMU code gets included. >> >> This issue was discussed a few weeks ago. No single approach appears to >> satisfy everyone. I like this because it depends upon one switch: Do you >> want DebugFS support enabled in the IOMMU driver, period? Vendor-specific >> code can then choose to implement support or not, and a builder doesn't have >> to worry about enabling/disabling multiple Kconfig options. >> >> At least, that was my line of reasoning. >> >> I'm not married to any approach, and I don't find clever use of Kconfig >> options too terribly challenging. And I'm not defending, I'm just >> explaining. > > The issue is, no one sets Kconfig options except a very tiny subset of > kernel developers. Distros allways enable everything, as they have to > do that. > > If you are creating something here that is so dangerous that you spam > the kernel log with big warning messages, you should not be making it > easy to enable, let alone be enabled by default :)
Okay, I get that. Totally understand.
> Just make it an option, have it rely on the kernel debugging option, and > say "DO NOT ENABLE THIS UNLESS YOU REALLY REALLY REALLY KNOW WHAT YOU > ARE DOING!"
Nah, Randy voted for separate options per device, on top of the IOMMU option. So I'll go with that. With loud messages, of course.
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