Hi, > From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi- > owner@xxxxxxxxxxxxxxx] On Behalf Of Octavian Purdila > Subject: Re: [RFC PATCH 02/10] acpi: install SSDT tables from initrd > > 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. [Lv Zheng] This sounds reasonable. Or you can rename it to CONFIG_ACPI_TABLE_UPGRADE and make it default 'y'. Also you need to remove acpi_table_taint() which is not so useful now. Thanks and best regards -Lv ��.n��������+%������w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
