Re: [Qemu-ppc] [Qemu-devel] [PATCH] Introduce machine specific default memory size

[Thomas Huth]

On Wed, 04 Mar 2015 14:59:13 +0530
Nikunj A Dadhania <address@hidden> wrote:

> Thomas Huth <address@hidden> writes:
> 
> > On Wed, 04 Mar 2015 14:34:27 +0530
> > Nikunj A Dadhania <address@hidden> wrote:
> >
> >> Thomas Huth <address@hidden> writes:
> >> 
> >> > On Wed, 04 Mar 2015 14:00:17 +0530
> >> > Nikunj A Dadhania <address@hidden> wrote:
> >> >
> >> >> Markus Armbruster <address@hidden> writes:
> >> >> 
> >> >> > Nikunj A Dadhania <address@hidden> writes:
> >> >> >
> >> >> >> diff --git a/vl.c b/vl.c
> >> >> >> index eb89d62..dd56754 100644
> >> >> >> --- a/vl.c
> >> >> >> +++ b/vl.c
> >> >> >> @@ -4053,6 +4053,18 @@ int main(int argc, char **argv, char **envp)
> >> >> >>          exit(1);
> >> >> >>      }
> >> >> >>  
> >> >> >> +    if (machine_class->default_ram_size && ram_size < 
> >> >> >> machine_class->default_ram_size) {
> >> >> >> +        fprintf(stderr, "qemu: %s guest ram size defaulting to %ld 
> >> >> >> MB\n",
> >> >> >> +                machine_class->name,
> >> >> >> +                machine_class->default_ram_size / (1024 * 1024));
> >> >> >
> >> >> > If the user explicitly asks for something, we either provide it
> >> >> > silently, or we error out.  This does neither.  Why?
> >> >> 
> >> >> In case the user has provided memory not enough to boot the machine, I
> >> >> could error out. My idea was to have a sane default which is provided by
> >> >> the machine.
> >> >> 
> >> >> Initially, I had just "ram_size == default_ram_size", but then it was
> >> >> allowing "-m 128M" to go through. And the VM would not boot. 
> >> >> 
> >> >> This can as well be converted to an error report and fail here to boot
> >> >> the VM.
> >> >
> >> > What does exactly fail with 128MB? Linux? 
> >> 
> >> Linux kernel, and not much info as well on the console.
> >
> > Ok, but then I think it should still be possible to specify -m 128M on
> > the command line - in case the user wants to run an older Linux which
> > still works fine with that amount of memory.
> 
> But how do we distinguish whether its old/new kernel in the distro?
> 
> And the older kernel will boot with more memory, while the reverse isnt
> true.

True, and it's IMHO certainly ok to increase the default memory size -
I just wanted to say that you should not disallow "-m 128M" in case the
users know what they are doing.

 Thomas