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Message-ID: <877fidx7p8.fsf@linux.vnet.ibm.com>
Date: Wed, 10 Feb 2016 14:28:43 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: David Gibson <david@...son.dropbear.id.au>, mpe@...erman.id.au,
paulus@...ba.org, benh@...nel.crashing.org
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH 2/4] powerpc/mm: Handle removing maybe-present bolted HPTEs
David Gibson <david@...son.dropbear.id.au> writes:
> At the moment the hpte_removebolted callback in ppc_md returns void and
> will BUG_ON() if the hpte it's asked to remove doesn't exist in the first
> place. This is awkward for the case of cleaning up a mapping which was
> partially made before failing.
>
> So, we add a return value to hpte_removebolted, and have it return ENOENT
> in the case that the HPTE to remove didn't exist in the first place.
>
> In the (sole) caller, we propagate errors in hpte_removebolted to its
> caller to handle. However, we handle ENOENT specially, continuing to
> complete the unmapping over the specified range before returning the error
> to the caller.
>
> This means that htab_remove_mapping() will work sanely on a partially
> present mapping, removing any HPTEs which are present, while also returning
> ENOENT to its caller in case it's important there.
>
> There are two callers of htab_remove_mapping():
> - In remove_section_mapping() we already WARN_ON() any error return,
> which is reasonable - in this case the mapping should be fully
> present
> - In vmemmap_remove_mapping() we BUG_ON() any error. We change that to
> just a WARN_ON() in the case of ENOENT, since failing to remove a
> mapping that wasn't there in the first place probably shouldn't be
> fatal.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> Signed-off-by: David Gibson <david@...son.dropbear.id.au>
> ---
> arch/powerpc/include/asm/machdep.h | 2 +-
> arch/powerpc/mm/hash_utils_64.c | 15 ++++++++++++---
> arch/powerpc/mm/init_64.c | 9 +++++----
> arch/powerpc/platforms/pseries/lpar.c | 9 ++++++---
> 4 files changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
> index 3f191f5..fa25643 100644
> --- a/arch/powerpc/include/asm/machdep.h
> +++ b/arch/powerpc/include/asm/machdep.h
> @@ -54,7 +54,7 @@ struct machdep_calls {
> int psize, int apsize,
> int ssize);
> long (*hpte_remove)(unsigned long hpte_group);
> - void (*hpte_removebolted)(unsigned long ea,
> + int (*hpte_removebolted)(unsigned long ea,
> int psize, int ssize);
> void (*flush_hash_range)(unsigned long number, int local);
> void (*hugepage_invalidate)(unsigned long vsid,
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 9f7d727..99fbee0 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -269,6 +269,8 @@ int htab_remove_mapping(unsigned long vstart, unsigned long vend,
> {
> unsigned long vaddr;
> unsigned int step, shift;
> + int rc;
> + int ret = 0;
>
> shift = mmu_psize_defs[psize].shift;
> step = 1 << shift;
> @@ -276,10 +278,17 @@ int htab_remove_mapping(unsigned long vstart, unsigned long vend,
> if (!ppc_md.hpte_removebolted)
> return -ENODEV;
>
> - for (vaddr = vstart; vaddr < vend; vaddr += step)
> - ppc_md.hpte_removebolted(vaddr, psize, ssize);
> + for (vaddr = vstart; vaddr < vend; vaddr += step) {
> + rc = ppc_md.hpte_removebolted(vaddr, psize, ssize);
> + if (rc == -ENOENT) {
> + ret = -ENOENT;
> + continue;
> + }
> + if (rc < 0)
> + return rc;
> + }
>
> - return 0;
> + return ret;
> }
> #endif /* CONFIG_MEMORY_HOTPLUG */
>
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index 379a6a9..baa1a23 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -232,10 +232,11 @@ static void __meminit vmemmap_create_mapping(unsigned long start,
> static void vmemmap_remove_mapping(unsigned long start,
> unsigned long page_size)
> {
> - int mapped = htab_remove_mapping(start, start + page_size,
> - mmu_vmemmap_psize,
> - mmu_kernel_ssize);
> - BUG_ON(mapped < 0);
> + int rc = htab_remove_mapping(start, start + page_size,
> + mmu_vmemmap_psize,
> + mmu_kernel_ssize);
> + BUG_ON((rc < 0) && (rc != -ENOENT));
> + WARN_ON(rc == -ENOENT);
> }
> #endif
>
> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
> index 477290a..2415a0d 100644
> --- a/arch/powerpc/platforms/pseries/lpar.c
> +++ b/arch/powerpc/platforms/pseries/lpar.c
> @@ -505,8 +505,8 @@ static void pSeries_lpar_hugepage_invalidate(unsigned long vsid,
> }
> #endif
>
> -static void pSeries_lpar_hpte_removebolted(unsigned long ea,
> - int psize, int ssize)
> +static int pSeries_lpar_hpte_removebolted(unsigned long ea,
> + int psize, int ssize)
> {
> unsigned long vpn;
> unsigned long slot, vsid;
> @@ -515,11 +515,14 @@ static void pSeries_lpar_hpte_removebolted(unsigned long ea,
> vpn = hpt_vpn(ea, vsid, ssize);
>
> slot = pSeries_lpar_hpte_find(vpn, psize, ssize);
> - BUG_ON(slot == -1);
> + if (slot == -1)
> + return -ENOENT;
> +
> /*
> * lpar doesn't use the passed actual page size
> */
> pSeries_lpar_hpte_invalidate(slot, vpn, psize, 0, ssize, 0);
> + return 0;
> }
>
> /*
> --
> 2.5.0
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...ts.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
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