On 2021/2/18 16:40, Baoquan He wrote: > On 01/30/21 at 03:10pm, Chen Zhou wrote: >> For arm64, the behavior of crashkernel=X has been changed, which >> tries low allocation in DMA zone and fall back to high allocation >> if it fails. >> >> We can also use "crashkernel=X,high" to select a high region above >> DMA zone, which also tries to allocate at least 256M low memory in >> DMA zone automatically and "crashkernel=Y,low" can be used to allocate >> specified size low memory. >> >> So update the Documentation. > Nice document adding which also takes care of x86 code implementation, > thanks. By the way, maybe you can remove John's 'Tested-by' since it > doesn't make much sense to test a document patch. I will remove the Tested-by in next version. > > Acked-by: Baoquan He <bhe@xxxxxxxxxx> > >> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx> >> Tested-by: John Donnelly <John.p.donnelly@xxxxxxxxxx> >> --- >> Documentation/admin-guide/kdump/kdump.rst | 22 ++++++++++++++++--- >> .../admin-guide/kernel-parameters.txt | 11 ++++++++-- >> 2 files changed, 28 insertions(+), 5 deletions(-) >> >> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst >> index 75a9dd98e76e..0877c76f8015 100644 >> --- a/Documentation/admin-guide/kdump/kdump.rst >> +++ b/Documentation/admin-guide/kdump/kdump.rst >> @@ -299,7 +299,16 @@ Boot into System Kernel >> "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory >> starting at physical address 0x01000000 (16MB) for the dump-capture kernel. >> >> - On x86 and x86_64, use "crashkernel=64M@16M". >> + On x86 use "crashkernel=64M@16M". >> + >> + On x86_64, use "crashkernel=X" to select a region under 4G first, and >> + fall back to reserve region above 4G. And go for high allocation >> + directly if the required size is too large. >> + We can also use "crashkernel=X,high" to select a region above 4G, which >> + also tries to allocate at least 256M below 4G automatically and >> + "crashkernel=Y,low" can be used to allocate specified size low memory. >> + Use "crashkernel=Y@X" if you really have to reserve memory from specified >> + start address X. >> >> On ppc64, use "crashkernel=128M@32M". >> >> @@ -316,8 +325,15 @@ Boot into System Kernel >> kernel will automatically locate the crash kernel image within the >> first 512MB of RAM if X is not given. >> >> - On arm64, use "crashkernel=Y[@X]". Note that the start address of >> - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000). >> + On arm64, use "crashkernel=X" to try low allocation in DMA zone and >> + fall back to high allocation if it fails. >> + We can also use "crashkernel=X,high" to select a high region above >> + DMA zone, which also tries to allocate at least 256M low memory in >> + DMA zone automatically. >> + "crashkernel=Y,low" can be used to allocate specified size low memory. >> + Use "crashkernel=Y@X" if you really have to reserve memory from >> + specified start address X. Note that the start address of the kernel, >> + X if explicitly specified, must be aligned to 2MiB (0x200000). >> >> Load the Dump-capture Kernel >> ============================ >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index a10b545c2070..908e5c8b61ba 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -738,6 +738,9 @@ >> [KNL, X86-64] Select a region under 4G first, and >> fall back to reserve region above 4G when '@offset' >> hasn't been specified. >> + [KNL, arm64] Try low allocation in DMA zone and fall back >> + to high allocation if it fails when '@offset' hasn't been >> + specified. >> See Documentation/admin-guide/kdump/kdump.rst for further details. >> >> crashkernel=range1:size1[,range2:size2,...][@offset] >> @@ -754,6 +757,8 @@ >> Otherwise memory region will be allocated below 4G, if >> available. >> It will be ignored if crashkernel=X is specified. >> + [KNL, arm64] range in high memory. >> + Allow kernel to allocate physical memory region from top. >> crashkernel=size[KMG],low >> [KNL, X86-64] range under 4G. When crashkernel=X,high >> is passed, kernel could allocate physical memory region >> @@ -762,13 +767,15 @@ >> requires at least 64M+32K low memory, also enough extra >> low memory is needed to make sure DMA buffers for 32-bit >> devices won't run out. Kernel would try to allocate at >> - at least 256M below 4G automatically. >> + least 256M below 4G automatically. >> This one let user to specify own low range under 4G >> for second kernel instead. >> 0: to disable low allocation. >> It will be ignored when crashkernel=X,high is not used >> or memory reserved is below 4G. >> - >> + [KNL, arm64] range in low memory. >> + This one let user to specify a low range in DMA zone for >> + crash dump kernel. >> cryptomgr.notests >> [KNL] Disable crypto self-tests >> >> -- >> 2.20.1 >> > . >
