On 11/07/18 at 05:10pm, lijiang wrote: > 在 2018年11月07日 13:23, Baoquan He 写道: > > On 11/07/18 at 01:00pm, Lianbo Jiang wrote: > >> E820 reserved ranges is useful in kdump kernel, it has been added in > >> kexec-tools code. > >> > >> One reason is PCI mmconf (extended mode) requires reserved region otherwise > >> it falls back to legacy mode, and also outputs the following kernel log. > > > > OK, it falls back to legacy mode, and also output kernel log, except of > > these, does it crash kernel? kdump kernel hang? Can we leave it if it > > only ouptut kernel log? > > > >> > >> Example: > >> ...... > >> [ 19.798354] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000) > >> [ 19.800653] [Firmware Info]: PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] not reserved in ACPI motherboard resources > >> [ 19.800995] PCI: not using MMCONFIG > >> ...... > >> > >> The correct kernel log is like this: > >> ...... > >> [ 0.082649] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000) > >> [ 0.083610] PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved in E820 > >> ...... > >> > >> Furthermore, when AMD SME kdump support, it needs to map dmi table area > >> as decrypted. For normal boot, these ranges sit in e820 reserved ranges, > >> thus the early ioremap code naturally map them as decrypted. If it also > >> has same e820 reserve setup in kdump kernel then it will just work like > >> normal kernel. > > > > Why do we care? If don't fix, what's happening? > > > > Lianbo, for a bug fix, please describe the problems. Then give out the > > analysis about root cause. > > > > Thanks for your comment in detail. > > In fact, these patches are really simple. As the subject mentioned, this patch > [PATCH 2/2] adds the reserved e820 ranges to kdump kernel e820 table, and the > first patch [PATCH 1/2] helps to exactly add the e820(E820_TYPE_RESERVED) type > to kdump kernel e820 table, that is to say, it will filter out some unnecessary > type(E820_TYPE_RAM/E820_TYPE_UNUSABLE/E820_TYPE_RESERVED_KERN). > > At present, when we use the kexec to load the kernel image and initramfs(for > example: kexec -s -p xxxx), the latest kernel does not pass the e820 reserved > ranges to the second kernel, which might produce two problems: > > The first one is the MMCONFIG issue, although which does not make the system > crash or hang, this issue is still a potential risk, because my test can't > cover all cases due to resource constraints(Machine), and i'm not sure what > it will happen on other machine. If a device is plugged in pci domain 1 then this device can not be recognized in kdump kernel in your case. For example if one want to dump to a network target, but the net card can not be recognized then vmcore can not be saved successfully Thanks Dave _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
