Subject: Re: [PATCH] powerepc/book3s64/hash: Align start address correctly with bolt mapping

From: Michael Ellerman <[email-masked]>
Date: Tue, 29 Oct 2019 22:08:47 +1100

"Aneesh Kumar K.V" <[email-masked]> writes:

> Without this we can miss mapping the last page covering the end address passed
>
> BUG: Unable to handle kernel data access at 0xc001000406000000
> Faulting instruction address: 0xc000000000090790
> NIP [c000000000090790] arch_add_memory+0xc0/0x130
> LR [c000000000090744] arch_add_memory+0x74/0x130
> Call Trace:
>  arch_add_memory+0x74/0x130 (unreliable)
>  memremap_pages+0x74c/0xa30
>  devm_memremap_pages+0x3c/0xa0
>  pmem_attach_disk+0x188/0x770
>  nvdimm_bus_probe+0xd8/0x470
>  really_probe+0x148/0x570
>  driver_probe_device+0x19c/0x1d0
>  device_driver_attach+0xcc/0x100
>  bind_store+0x134/0x1c0
>  drv_attr_store+0x44/0x60
>  sysfs_kf_write+0x74/0xc0
>  kernfs_fop_write+0x1b4/0x290
>  __vfs_write+0x3c/0x70
>  vfs_write+0xd0/0x260
>  ksys_write+0xdc/0x130
>  system_call+0x5c/0x68
>
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>  arch/powerpc/mm/book3s64/hash_utils.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Presumably you want this backported to kernels that have any nvdimm
support on powerpc?

cheers

> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
> index 6c123760164e..f66a1c6922d6 100644
> --- a/arch/powerpc/mm/book3s64/hash_utils.c
> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> @@ -257,8 +257,10 @@ int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
>  	DBG("htab_bolt_mapping(%lx..%lx -> %lx (%lx,%d,%d)\n",
>  	    vstart, vend, pstart, prot, psize, ssize);
>  
> -	for (vaddr = vstart, paddr = pstart; vaddr < vend;
> -	     vaddr += step, paddr += step) {
> +	vaddr = ALIGN_DOWN(vstart, step);
> +	paddr = ALIGN_DOWN(pstart, step);
> +
> +	for (; vaddr < vend; vaddr += step, paddr += step) {
>  		unsigned long hash, hpteg;
>  		unsigned long vsid = get_kernel_vsid(vaddr, ssize);
>  		unsigned long vpn  = hpt_vpn(vaddr, vsid, ssize);
> -- 
> 2.21.0