Re: [Qemu-devel] [PATCH v3] hw/i386: Deprecate the machines pc-0.10 to pc-1.2

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Jul 13, 2017 at 02:23:39AM +0200, Laszlo Ersek wrote:
> On 07/13/17 00:27, Michael S. Tsirkin wrote:
> > On Wed, Jul 12, 2017 at 05:56:46PM -0300, Eduardo Habkost wrote:
> >> On Wed, Jul 12, 2017 at 11:31:59PM +0300, Michael S. Tsirkin wrote:
> >>> On Wed, Jul 12, 2017 at 05:15:50PM -0300, Eduardo Habkost wrote:
> >>>> On Wed, Jul 12, 2017 at 06:17:55PM +0300, Michael S. Tsirkin wrote:
> >>>>> On Wed, Jul 12, 2017 at 11:51:21AM -0300, Eduardo Habkost wrote:
> >>>>>> On Wed, Jul 12, 2017 at 10:22:33AM +0200, Thomas Huth wrote:
> >>>>>>> We don't want to carry along old machine types forever. If we are able to
> >>>>>>> remove the pc machines up to 0.13 one day for example, this would allow
> >>>>>>> us to eventually kill the code for rombar=0 (i.e. where QEMU copies ROM
> >>>>>>> BARs directly to low memory). Everything up to pc-1.2 is also known to
> >>>>>>> have issues with migration.  So let's start with a deprecation message
> >>>>>>> for the old machine types so that the (hopefully) few users of these old
> >>>>>>> systems start switching over to newer machine types instead.
> >>>>>>>
> >>>>>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
> >>>>>>
> >>>>>> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> >>>>>>
> >>>>>> I suggest changing "-machine help" too.  Today it looks like this:
> >>>>>>
> >>>>>>   Supported machines are:
> >>>>>>   pc-i440fx-2.9        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.8        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.7        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.6        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.5        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.4        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.3        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.2        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc                   Standard PC (i440FX + PIIX, 1996) (alias of pc-i440fx-2.10)
> >>>>>>   pc-i440fx-2.10       Standard PC (i440FX + PIIX, 1996) (default)
> >>>>>>   pc-i440fx-2.1        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-2.0        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-1.7        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-1.6        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-1.5        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-i440fx-1.4        Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-1.3               Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-1.2               Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-1.1               Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-1.0               Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.15              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.14              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.13              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.12              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.11              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-0.10              Standard PC (i440FX + PIIX, 1996)
> >>>>>>   pc-q35-2.9           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   pc-q35-2.8           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   pc-q35-2.7           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   pc-q35-2.6           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   pc-q35-2.5           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   pc-q35-2.4           Standard PC (Q35 + ICH9, 2009)
> >>>>>>   q35                  Standard PC (Q35 + ICH9, 2009) (alias of pc-q35-2.10)
> >>>>>>   pc-q35-2.10          Standard PC (Q35 + ICH9, 2009)
> >>>>>>   isapc                ISA-only PC
> >>>>>>   none                 empty machine
> >>>>>
> >>>>> Any chance we can sort them reasonably too?
> >>>>
> >>>> If we use strverscmp(), it will be sorted in a more reasonable
> >>>> way.  We could copy the gnulib version on systems without glibc.
> >>>> Life is too short for writing configure checks by hand, though; I
> >>>> will add this to the end of my wish-todo list.  If somebody wants
> >>>> to volunteer, be my guest.
> >>>>
> >>>> I'm CCing Eric in case he has suggestions that would help import
> >>>> the gnulib module in an easy way.
> >>>>
> >>>> -- 
> >>>> Eduardo
> >>>
> >>> As we never have leading zeroes, and input comes from QEMU so
> >>> it's safe, it's probably easier to just open-code it:
> >>>
> >>> /* compare string numerically: shorter strings give smaller numbers */
> >>> int mstcmp(const char *s1, const char *s2)
> >>> {
> >>> 	int l1, l2;
> >>>
> >>> 	l1 = strlen(s1);
> >>> 	l2 = strlen(s2);
> >>> 	return l1 == l2 ? strcmp(s1, s2) : l1 - l2;
> >>> }
> >>>
> >>
> >> This doesn't work because strlen("pc-0.10") > strlen("pc-1.0").
> > 
> > Oh right. So you need to find dots and split at these points.
> > Something like the below? Completely untested.
> > 
> > int mstcmp(const char *s1, const char *s2)
> > {
> > 	const char *e1, *e2;
> >  	int l1, l2, c;
> > 
> > 	do {
> > 		e1 = strchr(s1, '.');
> > 		e2 = strchr(s2, '.');
> > 
> > 		l1 = e1 ? e1 - s1 + 1 : strlen(s1);
> > 		l2 = e2 ? e2 - s2 + 1 : strlen(s2);
> > 
> > 		/* compare numerically: shorter strings give smaller numbers */
> > 		if (l1 != l2) {
> > 			break;
> > 		}
> > 		c = strncmp(s1, s2, l1);
> > 		if (c) {
> > 			return c;
> > 		}
> > 		s1 += l1;
> > 		s2 += l1;
> > 	} while (l1);
> > 
> > 	return l1 - l2;
> > }

I believe copying strverscmp() from gnulib as-is is better than
reimplementing a subset of it.

> 
> QEMU already has machine type sorting code:
> 
>   1  2709f263952b well-defined listing order for machine types
>   2  562542b6aee2 i386/pc: add piix and q35 machtypes to sorting
>                   families for -M \?
> 
> I guess it should be possible to refine machine_class_cmp() in "vl.c",
> so that some numeric sorting is applied to machine types in the same
> "family".

Yes.  My suggestion is to use strverscmp() inside
machine_class_cmp().

-- 
Eduardo