On 06/27/22 at 03:44pm, Tao Liu wrote: > The total memory size we get in kernel is usually slightly less than > the actual memory size because BIOS/firmware will reserve some memory > region. So it won't export all memory as usable. > > E.g, on my x86_64 kvm guest with 1G memory, the total_mem value shows: > UEFI boot with ovmf: 0x3faef000 > Legacy boot kvm guest: 0x3ff7ec00 > > When specifying crashkernel=1G-2G:128M, if we have a 1G memory machine, > we get total size 1023M from firmware. Then it will not fall into > 1G-2G, thus no memory reserved. User will never know this, it is hard > to let user know the exact total value in kernel. > > One way is to use dmi/smbios to get physical memory size, but it's not > reliable as well. According to Prarit hardware vendors sometimes screw > this up. Thus round up total size to 128M to work around this problem. > > This patch is a resend of [1] and rebased onto v5.19-rc2, and the > original credit goes to Dave Young <dyoung@xxxxxxxxxx>. This should be put into cover letter, or put together with change log. Other than this, LGTM, Acked-by: Baoquan He <bhe@xxxxxxxxxx> > > [1]: http://lists.infradead.org/pipermail/kexec/2018-April/020568.html > > Signed-off-by: Tao Liu <ltao@xxxxxxxxxx> > --- > v1 -> v2: > Modified commit log based on Baoquan's advice. > --- > kernel/crash_core.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 71122e01623c..b58b27cbdb61 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -9,6 +9,7 @@ > #include <linux/init.h> > #include <linux/utsname.h> > #include <linux/vmalloc.h> > +#include <linux/sizes.h> > > #include <asm/page.h> > #include <asm/sections.h> > @@ -43,6 +44,15 @@ static int __init parse_crashkernel_mem(char *cmdline, > unsigned long long *crash_base) > { > char *cur = cmdline, *tmp; > + unsigned long long total_mem = system_ram; > + > + /* > + * Firmware sometimes reserves some memory regions for its own use, > + * so the system memory size is less than the actual physical memory > + * size. Work around this by rounding up the total size to 128M, > + * which is enough for most test cases. > + */ > + total_mem = roundup(total_mem, SZ_128M); > > /* for each entry of the comma-separated list */ > do { > @@ -87,13 +97,13 @@ static int __init parse_crashkernel_mem(char *cmdline, > return -EINVAL; > } > cur = tmp; > - if (size >= system_ram) { > + if (size >= total_mem) { > pr_warn("crashkernel: invalid size\n"); > return -EINVAL; > } > > /* match ? */ > - if (system_ram >= start && system_ram < end) { > + if (total_mem >= start && total_mem < end) { > *crash_size = size; > break; > } > -- > 2.33.1 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
