Hi, > From: Dou Liyang [mailto:douly.f...@cn.fujitsu.com] > Sent: Tuesday, July 18, 2017 5:44 PM > Subject: Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization > earlier > > Hi Baoquan, > > At 07/18/2017 04:45 PM, b...@redhat.com wrote: > > On 07/18/17 at 02:08pm, Dou Liyang wrote: > >> Hi, Zheng > >> > >> At 07/18/2017 01:18 PM, Zheng, Lv wrote: > >>> Hi, > >>> > >>> Can the problem be fixed by invoking acpi_put_table() for mapped DMAR > >>> table? > >> > >> Invoking acpi_put_table() is my first choice. But it made the kernel > >> *panic* when we try to get the table again in intel_iommu_init() in > >> late stage. > >> > >> I am also confused that: > >> > >> There are two places where we used DMAR table in Linux: > >> > >> 1) In detect_intel_iommu() in ACPI early stage: > >> > >> ... > >> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl); > >> .... > >> if (dmar_tbl) { > >> acpi_put_table(dmar_tbl); > >> dmar_tbl = NULL; > >> } > >> > >> 2) In dmar_table_init() in ACPI late stage: > >> > >> ... > >> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl); > >> ... > >> > >> As we know, dmar_table_init() is called by intel_iommu_init() and > >> intel_prepare_irq_remapping(). > >> > >> When I invoked acpi_put_table() in the intel_prepare_irq_remapping() in > >> early stage like 1) shows, kernel will panic. > > > > That's because acpi_put_table() will make the table pointer be NULL, > > while dmar_table_init() will skip parse_dmar_table() calling if > > dmar_table_initialized is set to 1 in intel_prepare_irq_remapping(). > > > > Correctly. > > I have considered and removed the *dmar_table_initialized* in this > situation. So, dmar_table_init() didn't skip parse_dmar_table() > calling. > > I didn't dig into the cause, I think it is interesting, I will do it > right now and share with you later. > > > Dmar hardware support interrupt remapping and io remapping separately. But > > intel_iommu_init() is called later than intel_prepare_irq_remapping(). > > So what if make dmar_table_init() a reentrant function? You can just > > have a try, but maybe not a good idea, the dmar table will be parsed > > twice. > > Yes, It is precisely one reason that I gave up invoking > acpi_put_table().
Parsing a table twice is not a problem on x86. If you check the code, there are many examples. It's actually required if you want to use a table both in early stage and late stage. Thanks > > Thanks, > > dou. > > > > >> > >> > >> Thanks, > >> > >> dou. > >>> > >>> Thanks > >>> Lv > >>> > >>>> From: Dou Liyang [mailto:douly.f...@cn.fujitsu.com] > >>>> Sent: Friday, July 14, 2017 1:53 PM > >>>> To: x...@kernel.org; linux-kernel@vger.kernel.org > >>>> Cc: t...@linutronix.de; mi...@kernel.org; h...@zytor.com; > >>>> ebied...@xmission.com; b...@redhat.com; > >>>> pet...@infradead.org; izumi.t...@jp.fujitsu.com; > >>>> tokunaga.kei...@jp.fujitsu.com; Dou Liyang > >>>> <douly.f...@cn.fujitsu.com>; linux-a...@vger.kernel.org; Rafael J. > >>>> Wysocki <r...@rjwysocki.net>; > Zheng, > >>>> Lv <lv.zh...@intel.com>; Julian Wollrath <jwollr...@web.de> > >>>> Subject: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization > >>>> earlier > >>>> > >>>> Linux uses acpi_early_init() to put the ACPI table management into > >>>> the late stage from the early stage where the mapped ACPI tables is > >>>> temporary and should be unmapped. > >>>> > >>>> But, now initializing interrupt delivery mode should map and parse the > >>>> DMAR table earlier in the early stage. This causes an ACPI error when > >>>> Linux reallocates the ACPI root tables. Because Linux doesn't unmapped > >>>> the DMAR table after using in the early stage. > >>>> > >>>> Invoke acpi_early_init() earlier before late_time_init(), Keep the DMAR > >>>> be mapped and parsed in late stage like before. > >>>> > >>>> Reported-by: Xiaolong Ye <xiaolong...@intel.com> > >>>> Signed-off-by: Dou Liyang <douly.f...@cn.fujitsu.com> > >>>> Cc: linux-a...@vger.kernel.org > >>>> Cc: Rafael J. Wysocki <r...@rjwysocki.net> > >>>> Cc: Zheng, Lv <lv.zh...@intel.com> > >>>> Cc: Julian Wollrath <jwollr...@web.de> > >>>> --- > >>>> Test in my own PC(Lenovo M4340). > >>>> Ask help for doing regression testing for the bug said in commit > >>>> c4e1acbb35e4 > >>>> ("ACPI / init: Invoke early ACPI initialization later"). > >>>> > >>>> init/main.c | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/init/main.c b/init/main.c > >>>> index df58a41..7a09467 100644 > >>>> --- a/init/main.c > >>>> +++ b/init/main.c > >>>> @@ -654,12 +654,12 @@ asmlinkage __visible void __init start_kernel(void) > >>>> kmemleak_init(); > >>>> setup_per_cpu_pageset(); > >>>> numa_policy_init(); > >>>> + acpi_early_init(); > >>>> if (late_time_init) > >>>> late_time_init(); > >>>> calibrate_delay(); > >>>> pidmap_init(); > >>>> anon_vma_init(); > >>>> - acpi_early_init(); > >>>> #ifdef CONFIG_X86 > >>>> if (efi_enabled(EFI_RUNTIME_SERVICES)) > >>>> efi_enter_virtual_mode(); > >>>> -- > >>>> 2.5.5 > >>>> > >>>> > >>> > >>> > >>> > >>> > >> > >> > > > > > > >
