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. 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 >
