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Date:      Fri, 29 Oct 2010 13:02:08 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        Attilio Rao <attilio@freebsd.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r214457 - in head/sys: amd64/amd64 conf i386/i386 x86/x86
Message-ID:  <201010291302.08687.jhb@freebsd.org>
In-Reply-To: <AANLkTimHcXs6MyTeL%2Bhc4BeYe5QBhAvkBbTQBWYONH8O@mail.gmail.com>
References:  <201010281631.o9SGVdtZ014923@svn.freebsd.org> <201010291026.20252.jhb@freebsd.org> <AANLkTimHcXs6MyTeL%2Bhc4BeYe5QBhAvkBbTQBWYONH8O@mail.gmail.com>

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On Friday, October 29, 2010 10:33:05 am Attilio Rao wrote:
> 2010/10/29 John Baldwin <jhb@freebsd.org>:
> > On Friday, October 29, 2010 10:17:23 am Attilio Rao wrote:
> >> 2010/10/29 John Baldwin <jhb@freebsd.org>:
> >> > On Thursday, October 28, 2010 8:25:38 pm Attilio Rao wrote:
> >> >> 2010/10/28 John Baldwin <jhb@freebsd.org>:
> >> >> > On Thursday, October 28, 2010 4:28:12 pm Attilio Rao wrote:
> >> >> >> 2010/10/28 John Baldwin <jhb@freebsd.org>:
> >> >> >> > On Thursday, October 28, 2010 1:21:34 pm Attilio Rao wrote:
> >> >> >> >> 2010/10/28 John Baldwin <jhb@freebsd.org>:
> >> >> >> >> > On Thursday, October 28, 2010 12:31:39 pm Attilio Rao wrote:
> >> >> >> >> >> Author: attilio
> >> >> >> >> >> Date: Thu Oct 28 16:31:39 2010
> >> >> >> >> >> New Revision: 214457
> >> >> >> >> >> URL: http://svn.freebsd.org/changeset/base/214457
> >> >> >> >> >>
> >> >> >> >> >> Log:
> >> >> >> >> >>   Merge nexus.c from amd64 and i386 to x86 subtree.
> >> >> >> >> >>
> >> >> >> >> >>   Sponsored by:       Sandvine Incorporated
> >> >> >> >> >>   Tested by:  gianni
> >> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> > It would be better to merge these two routines.  The loader now passes
> >> >> > the
> >> >> >> >> > smap to i386 kernels as well, so ram_attach() should probably be
> >> >> > changed to
> >> >> >> >> > try the amd64 approach first and if that fails fall back to using the
> >> >> >> >> > phys_avail[] array instead.
> >> >> >> >>
> >> >> >> >> What do you think about this patch?:
> >> >> >> >> Index: nexus.c
> >> >> >> >> ===================================================================
> >> >> >> >> --- nexus.c     (revision 214457)
> >> >> >> >> +++ nexus.c     (working copy)
> >> >> >> >> @@ -52,9 +52,7 @@
> >> >> >> >>  #include <sys/systm.h>
> >> >> >> >>  #include <sys/bus.h>
> >> >> >> >>  #include <sys/kernel.h>
> >> >> >> >> -#ifdef __amd64__
> >> >> >> >>  #include <sys/linker.h>
> >> >> >> >> -#endif
> >> >> >> >>  #include <sys/malloc.h>
> >> >> >> >>  #include <sys/module.h>
> >> >> >> >>  #include <machine/bus.h>
> >> >> >> >> @@ -67,12 +65,10 @@
> >> >> >> >>  #include <vm/pmap.h>
> >> >> >> >>  #include <machine/pmap.h>
> >> >> >> >>
> >> >> >> >> -#ifdef __amd64__
> >> >> >> >>  #include <machine/metadata.h>
> >> >> >> >> -#include <machine/pc/bios.h>
> >> >> >> >> -#endif
> >> >> >> >>  #include <machine/nexusvar.h>
> >> >> >> >>  #include <machine/resource.h>
> >> >> >> >> +#include <machine/pc/bios.h>
> >> >> >> >>
> >> >> >> >>  #ifdef DEV_APIC
> >> >> >> >>  #include "pcib_if.h"
> >> >> >> >> @@ -89,11 +85,13 @@
> >> >> >> >>  #include <sys/rtprio.h>
> >> >> >> >>
> >> >> >> >>  #ifdef __amd64__
> >> >> >> >> -#define        RMAN_BUS_SPACE_IO       AMD64_BUS_SPACE_IO
> >> >> >> >> -#define        RMAN_BUS_SPACE_MEM      AMD64_BUS_SPACE_MEM
> >> >> >> >> +#define        X86_BUS_SPACE_IO        AMD64_BUS_SPACE_IO
> >> >> >> >> +#define        X86_BUS_SPACE_MEM       AMD64_BUS_SPACE_MEM
> >> >> >> >> +#define        ELF_KERN_STR            "elf64 kernel"
> >> >> >> >>  #else
> >> >> >> >> -#define        RMAN_BUS_SPACE_IO       I386_BUS_SPACE_IO
> >> >> >> >> -#define        RMAN_BUS_SPACE_MEM      I386_BUS_SPACE_MEM
> >> >> >> >> +#define        X86_BUS_SPACE_IO        I386_BUS_SPACE_IO
> >> >> >> >> +#define        X86_BUS_SPACE_MEM       I386_BUS_SPACE_MEM
> >> >> >> >> +#define        ELF_KERN_STR            "elf32 kernel"
> >> >> >> >>  #endif
> >> >> >> >> @@ -701,16 +699,11 @@
> >> >> >> >>                         panic("ram_attach: resource %d failed to attach",
> >> >> > rid);
> >> >> >> >>                 rid++;
> >> >> >> >>         }
> >> >> >> >> -       return (0);
> >> >> >> >> -}
> >> >> >> >> -#else
> >> >> >> >> -static int
> >> >> >> >> -ram_attach(device_t dev)
> >> >> >> >> -{
> >> >> >> >> -       struct resource *res;
> >> >> >> >> -       vm_paddr_t *p;
> >> >> >> >> -       int error, i, rid;
> >> >> >> >>
> >> >> >> >> +       /* If at least one smap attached, return. */
> >> >> >> >> +       if (rid != 0)
> >> >> >> >> +               return (0);
> >> >> >> >> +
> >> >> >> >
> >> >> >> > Perhaps this instead:
> >> >> >> >
> >> >> >> >        /* If we found an SMAP, return. */
> >> >> >> >        if (smapbase != NULL)
> >> >> >> >                return (0);
> >> >> >>
> >> >> >> No, I don't think this check is right, smapbase will always be != NULL
> >> >> >> (otherwise the code panics).
> >> >> >
> >> >> > Oh, that needs to be fixed then.  It can be NULL on i386 with an old loader
> >> >> > (or on a really old machine without an SMAP).  The amd64 nexus code could
> >> >> > assume it would never be NULL, but i386 cannot.
> >> >> >
> >> >> > It should probably more closely match what i386 does during the memory probe
> >> >> > which is:
> >> >> >
> >> >> >        kmdp = search("elf kernel");
> >> >> >        if (kmdp == NULL)
> >> >> >                kmdp = search("elfXX kernel");
> >> >> >        if (kmdp != NULL)
> >> >> >                smapbase = preload_search(...);
> >> >> >        else
> >> >> >                smapbase = NULL;
> >> >> >        if (smapbase != NULL) {
> >> >> >                for (smap = ...) {
> >> >> >                }
> >> >> >
> >> >> >                return (0);
> >> >> >        }
> >> >> >
> >> >> >        /* fall through to old i386 code using phys_avail[] */
> >> >>
> >> >> This further patch should address your concerns about nexus.c:
> >> >> Index: nexus.c
> >> >> ===================================================================
> >> >> --- nexus.c     (revision 214457)
> >> >> +++ nexus.c     (working copy)
> >> >> @@ -52,9 +52,7 @@
> >> >>  #include <sys/systm.h>
> >> >>  #include <sys/bus.h>
> >> >>  #include <sys/kernel.h>
> >> >> -#ifdef __amd64__
> >> >>  #include <sys/linker.h>
> >> >> -#endif
> >> >>  #include <sys/malloc.h>
> >> >>  #include <sys/module.h>
> >> >>  #include <machine/bus.h>
> >> >> @@ -67,12 +65,10 @@
> >> >>  #include <vm/pmap.h>
> >> >>  #include <machine/pmap.h>
> >> >>
> >> >> -#ifdef __amd64__
> >> >>  #include <machine/metadata.h>
> >> >> -#include <machine/pc/bios.h>
> >> >> -#endif
> >> >>  #include <machine/nexusvar.h>
> >> >>  #include <machine/resource.h>
> >> >> +#include <machine/pc/bios.h>
> >> >>
> >> >>  #ifdef DEV_APIC
> >> >>  #include "pcib_if.h"
> >> >> @@ -89,13 +85,15 @@
> >> >>  #include <sys/rtprio.h>
> >> >>
> >> >>  #ifdef __amd64__
> >> >> -#define        RMAN_BUS_SPACE_IO       AMD64_BUS_SPACE_IO
> >> >> -#define        RMAN_BUS_SPACE_MEM      AMD64_BUS_SPACE_MEM
> >> >> +#define        BUS_SPACE_IO    AMD64_BUS_SPACE_IO
> >> >> +#define        BUS_SPACE_MEM   AMD64_BUS_SPACE_MEM
> >> >>  #else
> >> >> -#define        RMAN_BUS_SPACE_IO       I386_BUS_SPACE_IO
> >> >> -#define        RMAN_BUS_SPACE_MEM      I386_BUS_SPACE_MEM
> >> >> +#define        BUS_SPACE_IO    I386_BUS_SPACE_IO
> >> >> +#define        BUS_SPACE_MEM   I386_BUS_SPACE_MEM
> >> >>  #endif
> >> >>
> >> >> +#define        ELF_KERN_STR    ("elf"__XSTRING(__ELF_WORD_SIZE)" kernel")
> >> >> +
> >> >>  static MALLOC_DEFINE(M_NEXUSDEV, "nexusdev", "Nexus device");
> >> >>
> >> >>  #define DEVTONX(dev)   ((struct nexus_device *)device_get_ivars(dev))
> >> >> @@ -435,7 +433,7 @@
> >> >>  #else
> >> >>                 rman_set_bushandle(r, rman_get_start(r));
> >> >>  #endif
> >> >> -               rman_set_bustag(r, RMAN_BUS_SPACE_IO);
> >> >> +               rman_set_bustag(r, BUS_SPACE_IO);
> >> >>                 break;
> >> >>         case SYS_RES_MEMORY:
> >> >>  #ifdef PC98
> >> >> @@ -446,7 +444,7 @@
> >> >>  #endif
> >> >>                 vaddr = pmap_mapdev(rman_get_start(r), rman_get_size(r));
> >> >>                 rman_set_virtual(r, vaddr);
> >> >> -               rman_set_bustag(r, RMAN_BUS_SPACE_MEM);
> >> >> +               rman_set_bustag(r, BUS_SPACE_MEM);
> >> >>  #ifdef PC98
> >> >>                 /* PC-98: the type of bus_space_handle_t is the structure. */
> >> >>                 bh->bsh_base = (bus_addr_t) vaddr;
> >> >> @@ -668,48 +666,45 @@
> >> >>         return (0);
> >> >>  }
> >> >>
> >> >> -#ifdef __amd64__
> >> >>  static int
> >> >>  ram_attach(device_t dev)
> >> >>  {
> >> >>         struct bios_smap *smapbase, *smap, *smapend;
> >> >>         struct resource *res;
> >> >> +       vm_paddr_t *p;
> >> >>         caddr_t kmdp;
> >> >>         uint32_t smapsize;
> >> >> -       int error, rid;
> >> >> +       int error, i, rid;
> >> >>
> >> >>         /* Retrieve the system memory map from the loader. */
> >> >>         kmdp = preload_search_by_type("elf kernel");
> >> >>         if (kmdp == NULL)
> >> >> -               kmdp = preload_search_by_type("elf64 kernel");
> >> >> -       smapbase = (struct bios_smap *)preload_search_info(kmdp,
> >> >> -           MODINFO_METADATA | MODINFOMD_SMAP);
> >> >> -       smapsize = *((u_int32_t *)smapbase - 1);
> >> >> -       smapend = (struct bios_smap *)((uintptr_t)smapbase + smapsize);
> >> >> +               kmdp = preload_search_by_type(ELF_KERN_STR);
> >> >> +       if (kmdp != NULL) {
> >> >> +               smapbase = (struct bios_smap *)preload_search_info(kmdp,
> >> >> +                   MODINFO_METADATA | MODINFOMD_SMAP);
> >> >> +               smapsize = *((u_int32_t *)smapbase - 1);
> >> >> +               smapend = (struct bios_smap *)((uintptr_t)smapbase + smapsize);
> >> >
> >> > I think this doesn't check for the case that smapbase is NULL.  I would
> >> > expect kmdp to always be non-NULL in practice (it just means we have a
> >> > kernel).  However, the preload_search_info() can fail when booting on an old
> >> > machine without an SMAP or an old loader that doesn't pass the SMAP to i386.
> >>
> >> I don't understand where is the problem.
> >> smap is only used when it is consistent in that patch, otherwise it is
> >> not used and fallsthrough the physavail[] approach.
> >> It doesn't need to be set to NULL or checked.
> >>
> >> I guess that you want to patch the file and see how it looks like,
> >> will be easier to review than inline .diff, in this case.
> >
> > The preload_search_info() can fail and return NULL (old machine with no SMAP
> > or an older /boot/loader on i386).  Then when you do this:
> >
> >        smapsize = *((u_int32_t *)smapbase - 1);
> >
> > the kernel will panic.
> 
> Ah, I thought that it could be failing only with a NULL kmdp.
> That patch should fix it then:

I think this looks fine, but I haven't tested it. :)

-- 
John Baldwin



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