* [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings
@ 2018-02-21 12:59 Will Deacon
2018-02-21 13:12 ` Ard Biesheuvel
2018-02-21 17:44 ` Catalin Marinas
0 siblings, 2 replies; 4+ messages in thread
From: Will Deacon @ 2018-02-21 12:59 UTC (permalink / raw)
To: linux-arm-kernel
ioremap_page_range doesn't honour break-before-make and attempts to put
down huge mappings (using p*d_set_huge) over the top of pre-existing
table entries. This leads to us leaking page table memory and also gives
rise to TLB conflicts and spurious aborts, which have been seen in
practice on Cortex-A75.
Until this has been resolved, refuse to put block mappings when the
existing entry is found to be present.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: Hanjun Guo <hanjun.guo@linaro.org>
Reported-by: Lei Li <lious.lilei@hisilicon.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/arm64/mm/mmu.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3161b853f29e..84a019f55022 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -933,6 +933,11 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
{
pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
pgprot_val(mk_sect_prot(prot)));
+
+ /* ioremap_page_range doesn't honour BBM */
+ if (pud_present(READ_ONCE(*pudp)))
+ return 0;
+
BUG_ON(phys & ~PUD_MASK);
set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
return 1;
@@ -942,6 +947,11 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
{
pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
pgprot_val(mk_sect_prot(prot)));
+
+ /* ioremap_page_range doesn't honour BBM */
+ if (pmd_present(READ_ONCE(*pmdp)))
+ return 0;
+
BUG_ON(phys & ~PMD_MASK);
set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
return 1;
--
2.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings
2018-02-21 12:59 [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings Will Deacon
@ 2018-02-21 13:12 ` Ard Biesheuvel
2018-02-21 17:44 ` Catalin Marinas
1 sibling, 0 replies; 4+ messages in thread
From: Ard Biesheuvel @ 2018-02-21 13:12 UTC (permalink / raw)
To: linux-arm-kernel
On 21 February 2018 at 12:59, Will Deacon <will.deacon@arm.com> wrote:
> ioremap_page_range doesn't honour break-before-make and attempts to put
> down huge mappings (using p*d_set_huge) over the top of pre-existing
> table entries. This leads to us leaking page table memory and also gives
> rise to TLB conflicts and spurious aborts, which have been seen in
> practice on Cortex-A75.
>
> Until this has been resolved, refuse to put block mappings when the
> existing entry is found to be present.
>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Reported-by: Hanjun Guo <hanjun.guo@linaro.org>
> Reported-by: Lei Li <lious.lilei@hisilicon.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
> arch/arm64/mm/mmu.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 3161b853f29e..84a019f55022 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -933,6 +933,11 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
> {
> pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
> pgprot_val(mk_sect_prot(prot)));
> +
> + /* ioremap_page_range doesn't honour BBM */
> + if (pud_present(READ_ONCE(*pudp)))
> + return 0;
> +
> BUG_ON(phys & ~PUD_MASK);
> set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
> return 1;
> @@ -942,6 +947,11 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
> {
> pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
> pgprot_val(mk_sect_prot(prot)));
> +
> + /* ioremap_page_range doesn't honour BBM */
> + if (pmd_present(READ_ONCE(*pmdp)))
> + return 0;
> +
> BUG_ON(phys & ~PMD_MASK);
> set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
> return 1;
This is a nice way of dealing with this IMO, as large mappings that
are only created at boot (e.g., for the ECAM space or gfx BARs) will
still use huge pages.
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings
2018-02-21 12:59 [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings Will Deacon
2018-02-21 13:12 ` Ard Biesheuvel
@ 2018-02-21 17:44 ` Catalin Marinas
2018-02-21 17:47 ` Will Deacon
1 sibling, 1 reply; 4+ messages in thread
From: Catalin Marinas @ 2018-02-21 17:44 UTC (permalink / raw)
To: linux-arm-kernel
On Wed, Feb 21, 2018 at 12:59:27PM +0000, Will Deacon wrote:
> ioremap_page_range doesn't honour break-before-make and attempts to put
> down huge mappings (using p*d_set_huge) over the top of pre-existing
> table entries. This leads to us leaking page table memory and also gives
> rise to TLB conflicts and spurious aborts, which have been seen in
> practice on Cortex-A75.
>
> Until this has been resolved, refuse to put block mappings when the
> existing entry is found to be present.
>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Reported-by: Hanjun Guo <hanjun.guo@linaro.org>
> Reported-by: Lei Li <lious.lilei@hisilicon.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
Queued for 4.16. Shall we put a cc stable?
--
Catalin
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings
2018-02-21 17:44 ` Catalin Marinas
@ 2018-02-21 17:47 ` Will Deacon
0 siblings, 0 replies; 4+ messages in thread
From: Will Deacon @ 2018-02-21 17:47 UTC (permalink / raw)
To: linux-arm-kernel
On Wed, Feb 21, 2018 at 05:44:24PM +0000, Catalin Marinas wrote:
> On Wed, Feb 21, 2018 at 12:59:27PM +0000, Will Deacon wrote:
> > ioremap_page_range doesn't honour break-before-make and attempts to put
> > down huge mappings (using p*d_set_huge) over the top of pre-existing
> > table entries. This leads to us leaking page table memory and also gives
> > rise to TLB conflicts and spurious aborts, which have been seen in
> > practice on Cortex-A75.
> >
> > Until this has been resolved, refuse to put block mappings when the
> > existing entry is found to be present.
> >
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Reported-by: Hanjun Guo <hanjun.guo@linaro.org>
> > Reported-by: Lei Li <lious.lilei@hisilicon.com>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
>
> Queued for 4.16. Shall we put a cc stable?
Yes, good idea:
Fixes: 324420bf91f60 ("arm64: add support for ioremap() block mappings")
Will
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-02-21 17:47 UTC | newest]
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2018-02-21 12:59 [PATCH] arm64: Enforce BBM for huge IO/VMAP mappings Will Deacon
2018-02-21 13:12 ` Ard Biesheuvel
2018-02-21 17:44 ` Catalin Marinas
2018-02-21 17:47 ` Will Deacon
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