On Tue, Apr 5, 2016 at 3:49 AM, Zheng, Lv <lv.zheng@xxxxxxxxx> wrote: > Hi, > >> From: Octavian Purdila [mailto:octavian.purdila@xxxxxxxxx] >> Subject: Re: [RFC PATCH 02/10] acpi: install SSDT tables from initrd >> >> On Fri, Apr 1, 2016 at 1:11 PM, Octavian Purdila >> <octavian.purdila@xxxxxxxxx> wrote: >> > On Fri, Apr 1, 2016 at 8:05 AM, Zheng, Lv <lv.zheng@xxxxxxxxx> wrote: >> >> Hi, >> >> >> >> IMO, there is already a similar function upstreamed: >> >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c85c >> c81 >> >> Could it work for your use case? >> > >> > Yes, it is basically the same. >> > >> > The only difference is on how we handle taint. I think we should use a >> > new taint for overlays and that we don't need to disable lockdep. >> > >> > BTW, why is lockdep disabled when we override? >> >> The other thing I forgot to mention is that I think we should allow >> installing new tables even if CONFIG_ACPI_INITRD_TABLE_OVERRIDE is not >> selected. IMO the override and overlay functionality is different, >> with the latter being more then a debug option. > [Lv Zheng] > I don't think so. The initrd override mechanism is not dependent on CONFIG_ACPI_DEBUG. > According to the spec, we can allow a higher versioning same table (same table sig, table id, table oem id) to override the old tables as a patching functionality. > So both the functionalities are not debug options and serve for the same purpose from this point of view. > And IMO that's why the initrd override mechanism needn't be dependent on CONFIG_ACPI_DEBUG. > The problem is that CONFIG_ACPI_INITRD_TABLE_OVERRIDE is presented as a debug option in Documentation/initrd_table_override.txt and most distributions are not selecting it which makes it hard to use it in practice. > I'm really OK with removing the acpi_table_taint() for CONFIG_ACPI_INITRD_TABLE_OVERRIDE but leaving some info messages indicating the table upgrades. > I don't think this mechanism is unsafe. > It happens during a initialization step occurring before the table is loaded and hence should be safe even the synchronization is not so robust in ACPICA. > And with the revision support added, we should be able to allow vendors to update the buggy tables. > That means the tables may be originated from the safe sources - the vendors. > >> >> I will prepare a patch for the next version of the series to decouple >> installing new tables from CONFIG_ACPI_INITRD_TABLE_OVERRIDE. > [Lv Zheng] > I don't think they need to be decoupled. > The use case is: > If there is an ACPI table in initrd image and: > 1. if the table's revision is higher than the existing one, override the existing one; > 2. if the table is a brand new one, install it. > The implementation will stay the same of course, I was just suggesting to move CONFIG_ACPI_INITRD_TABLE_OVERRIDE in acpi_os_physical_table_override to allow new tables to be loaded even if the option is not selected. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
