diff mbox series

powerpc: align memory_limit to 16MB in early_parse_mem

Message ID 20240301203023.2197451-1-jsavitz@redhat.com
State New
Headers
Series powerpc: align memory_limit to 16MB in early_parse_mem |

Commit Message

Joel Savitz March 1, 2024, 8:30 p.m. UTC 
  On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
cmdline parameter results in a system hang at boot.

For example, using 'mem=4198400K' will always reproduce this issue.

This patch fixes the problem by aligning any argument to mem= to 16MB
corresponding with the large page size on powerpc.

Fixes: 2babf5c2ec2f ("[PATCH] powerpc: Unify mem= handling")
Co-developed-by: Gonzalo Siero <gsierohu@redhat.com>
Signed-off-by: Gonzalo Siero <gsierohu@redhat.com>
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
---
 arch/powerpc/kernel/prom.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Michael Ellerman March 1, 2024, 11:23 p.m. UTC | #1 
Hi Joel,

Joel Savitz <jsavitz@redhat.com> writes:
> On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
> cmdline parameter results in a system hang at boot.

Can you give us any more details on that? It might be a bug we can fix.

> For example, using 'mem=4198400K' will always reproduce this issue.
>
> This patch fixes the problem by aligning any argument to mem= to 16MB
> corresponding with the large page size on powerpc.

The large page size depends on the MMU, with Radix it's 2MB or 1GB. So
depending on what's happening 16MB may not be enough.

What system are you testing on?

cheers

> Fixes: 2babf5c2ec2f ("[PATCH] powerpc: Unify mem= handling")
> Co-developed-by: Gonzalo Siero <gsierohu@redhat.com>
> Signed-off-by: Gonzalo Siero <gsierohu@redhat.com>
> Signed-off-by: Joel Savitz <jsavitz@redhat.com>
> ---
>  arch/powerpc/kernel/prom.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 0b5878c3125b..8cd3e2445d8a 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -82,8 +82,12 @@ static int __init early_parse_mem(char *p)
>  {
>  	if (!p)
>  		return 1;
> -
> +#ifdef CONFIG_PPC64
> +	/* Align to 16 MB == size of ppc64 large page */
> +	memory_limit = ALIGN(memparse(p, &p), 0x1000000);
> +#else
>  	memory_limit = PAGE_ALIGN(memparse(p, &p));
> +#endif
>  	DBG("memory limit = 0x%llx\n", memory_limit);
>  
>  	return 0;
> -- 
> 2.43.0
Joel Savitz March 2, 2024, 11:59 p.m. UTC | #2 
On Fri, Mar 1, 2024 at 6:23 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Hi Joel,
>
> Joel Savitz <jsavitz@redhat.com> writes:
> > On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
> > cmdline parameter results in a system hang at boot.
>
> Can you give us any more details on that? It might be a bug we can fix.

The console freezes after the following output:

  Booting a command list

OF stdout device is: /vdevice/vty@30000000
Preparing to boot Linux version 6.8.0-rc6.memNOfix-00120-g87adedeba51a
(root@ibm-p9z-26-lp11.virt.pnr.lab.eng.rdu2.redhat.com) (gcc (GCC)
11.4.1 20231218 (Red Hat 11.4.1-3), GNU ld version 2.35.2-43.el9) #3
SMP Fri Mar  1 10:45:45 EST 2024
Detected machine type: 0000000000000101
command line: BOOT_IMAGE=(ieee1275//vdevice/v-scsi@30000003/disk@8100000000000000,msdos2)/vmlinuz-6.8.0-rc6.memNOfix-00120-g87adedeba51a
root=/dev/mapper/rhel_ibm--p9z--26--lp11-root ro
crashkernel=2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G
rd.lvm.lv=rhel_ibm-p9z-26-lp11/root
rd.lvm.lv=rhel_ibm-p9z-26-lp11/swap mem=4198400K
Max number of cores passed to firmware: 256 (NR_CPUS = 2048)
Calling ibm,client-architecture-support... done
Ignoring mem=0000000101000000 >= ram_top.
memory layout at init:
  memory_limit : 0000000000000000 (16 MB aligned)
  alloc_bottom : 00000000114f0000
  alloc_top    : 0000000020000000
  alloc_top_hi : 0000000020000000
  rmo_top      : 0000000020000000
  ram_top      : 0000000020000000
instantiating rtas at 0x000000001ecb0000... done
prom_hold_cpus: skipped
copying OF device tree...
Building dt strings...
Building dt structure...
Device tree strings 0x0000000011500000 -> 0x00000000115017b7
Device tree struct  0x0000000011510000 -> 0x0000000011520000
Quiescing Open Firmware ...
Booting Linux via __start() @ 0x000000000a6e0000 ...

>
> > For example, using 'mem=4198400K' will always reproduce this issue.
> >
> > This patch fixes the problem by aligning any argument to mem= to 16MB
> > corresponding with the large page size on powerpc.
>
> The large page size depends on the MMU, with Radix it's 2MB or 1GB. So
> depending on what's happening 16MB may not be enough.
>
> What system are you testing on?

I'm running a virtual system in PowerVM on an IBM Z mainframe, 8375-42A model.

Best,
Joel Savitz

>
> cheers
>
> > Fixes: 2babf5c2ec2f ("[PATCH] powerpc: Unify mem= handling")
> > Co-developed-by: Gonzalo Siero <gsierohu@redhat.com>
> > Signed-off-by: Gonzalo Siero <gsierohu@redhat.com>
> > Signed-off-by: Joel Savitz <jsavitz@redhat.com>
> > ---
> >  arch/powerpc/kernel/prom.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> > index 0b5878c3125b..8cd3e2445d8a 100644
> > --- a/arch/powerpc/kernel/prom.c
> > +++ b/arch/powerpc/kernel/prom.c
> > @@ -82,8 +82,12 @@ static int __init early_parse_mem(char *p)
> >  {
> >       if (!p)
> >               return 1;
> > -
> > +#ifdef CONFIG_PPC64
> > +     /* Align to 16 MB == size of ppc64 large page */
> > +     memory_limit = ALIGN(memparse(p, &p), 0x1000000);
> > +#else
> >       memory_limit = PAGE_ALIGN(memparse(p, &p));
> > +#endif
> >       DBG("memory limit = 0x%llx\n", memory_limit);
> >
> >       return 0;
> > --
> > 2.43.0
>
Aneesh Kumar K.V March 4, 2024, 6:58 a.m. UTC | #3 
On 3/2/24 4:53 AM, Michael Ellerman wrote:
> Hi Joel,
> 
> Joel Savitz <jsavitz@redhat.com> writes:
>> On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
>> cmdline parameter results in a system hang at boot.
> 
> Can you give us any more details on that? It might be a bug we can fix.
> 
>> For example, using 'mem=4198400K' will always reproduce this issue.
>>
>> This patch fixes the problem by aligning any argument to mem= to 16MB
>> corresponding with the large page size on powerpc.
> 
> The large page size depends on the MMU, with Radix it's 2MB or 1GB. So
> depending on what's happening 16MB may not be enough.
> 
> What system are you testing on?
> 

htab_bolt_mapping should have aligned things to a lower value that is 16MB aligned.

	/* Carefully map only the possible range */
	vaddr = ALIGN(vstart, step);
	paddr = ALIGN(pstart, step);
	vend  = ALIGN_DOWN(vend, step);



-aneesh
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 0b5878c3125b..8cd3e2445d8a 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -82,8 +82,12 @@  static int __init early_parse_mem(char *p)
 {
 	if (!p)
 		return 1;
-
+#ifdef CONFIG_PPC64
+	/* Align to 16 MB == size of ppc64 large page */
+	memory_limit = ALIGN(memparse(p, &p), 0x1000000);
+#else
 	memory_limit = PAGE_ALIGN(memparse(p, &p));
+#endif
 	DBG("memory limit = 0x%llx\n", memory_limit);
 
 	return 0;