Commit ff172d4818ad ("riscv: Use hugepage mappings for vmemmap") broke XIP
kernel, because huge pages are not supported on XIP kernel.
Only use hugepage mapping if it is supported.
Fixes: ff172d4818ad ("riscv: Use hugepage mappings for vmemmap")
Signed-off-by: Nam Cao <[email protected]>
Cc: Alexandre Ghiti <[email protected]>
Cc: <[email protected]>
---
arch/riscv/mm/init.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 968761843203..c081e7d349b1 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1414,6 +1414,8 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
struct vmem_altmap *altmap)
{
+ if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP))
+ return vmemmap_populate_basepages(start, end, node, NULL);
/*
* Note that SPARSEMEM_VMEMMAP is only selected for rv64 and that we
* can't use hugepage mappings for 2-level page table because in case of
--
2.39.2
Hi Nam,
On 08/05/2024 19:31, Nam Cao wrote:
> Commit ff172d4818ad ("riscv: Use hugepage mappings for vmemmap") broke XIP
> kernel, because huge pages are not supported on XIP kernel.
I don't understand why XIP kernels can't support huge vmalloc mappings,
so I think the right fix would be to enable such mappings on XIP. WDYT?
Thanks,
Alex
>
> Only use hugepage mapping if it is supported.
>
> Fixes: ff172d4818ad ("riscv: Use hugepage mappings for vmemmap")
> Signed-off-by: Nam Cao <[email protected]>
> Cc: Alexandre Ghiti <[email protected]>
> Cc: <[email protected]>
> ---
> arch/riscv/mm/init.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 968761843203..c081e7d349b1 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1414,6 +1414,8 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> struct vmem_altmap *altmap)
> {
> + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP))
> + return vmemmap_populate_basepages(start, end, node, NULL);
> /*
> * Note that SPARSEMEM_VMEMMAP is only selected for rv64 and that we
> * can't use hugepage mappings for 2-level page table because in case of
On Wed, May 08, 2024 at 08:22:43PM +0200, Alexandre Ghiti wrote:
> Hi Nam,
Hi Alex,
> > Commit ff172d4818ad ("riscv: Use hugepage mappings for vmemmap") broke XIP
> > kernel, because huge pages are not supported on XIP kernel.
>
> I don't understand why XIP kernels can't support huge vmalloc mappings,
Me neither.
> so I
> think the right fix would be to enable such mappings on XIP. WDYT?
I agree that is the ideal solution. But I don't want to send any new
feature to the stable trees (stable folks may even reject such patch).
So I intend that to be in another patch.
Best regards,
Nam
Hi Nam,
On 08/05/2024 20:46, Nam Cao wrote:
> On Wed, May 08, 2024 at 08:22:43PM +0200, Alexandre Ghiti wrote:
>> Hi Nam,
> Hi Alex,
>
>>> Commit ff172d4818ad ("riscv: Use hugepage mappings for vmemmap") broke XIP
>>> kernel, because huge pages are not supported on XIP kernel.
>> I don't understand why XIP kernels can't support huge vmalloc mappings,
> Me neither.
>
>> so I
>> think the right fix would be to enable such mappings on XIP. WDYT?
> I agree that is the ideal solution. But I don't want to send any new
> feature to the stable trees (stable folks may even reject such patch).
> So I intend that to be in another patch.
I have been thinking about that, and I actually think that the real fix
is enabling huge vmalloc mappings for XIP as it was an oversight/mistake
in the first place. On 64-bit kernels, there are no reasons we can't use
PMD mappings for vmalloc. So I'd rather not go with this fix.
Thanks,
Alex
>
> Best regards,
> Nam
On Fri, May 24, 2024 at 10:07:40PM +0200, Alexandre Ghiti wrote:
> Hi Nam,
Hi Alex,
> On 08/05/2024 20:46, Nam Cao wrote:
> > On Wed, May 08, 2024 at 08:22:43PM +0200, Alexandre Ghiti wrote:
> > > > Commit ff172d4818ad ("riscv: Use hugepage mappings for vmemmap") broke XIP
> > > > kernel, because huge pages are not supported on XIP kernel.
> > > I don't understand why XIP kernels can't support huge vmalloc mappings,
> > Me neither.
> >
> > > so I
> > > think the right fix would be to enable such mappings on XIP. WDYT?
> > I agree that is the ideal solution. But I don't want to send any new
> > feature to the stable trees (stable folks may even reject such patch).
> > So I intend that to be in another patch.
>
>
> I have been thinking about that, and I actually think that the real fix is
> enabling huge vmalloc mappings for XIP as it was an oversight/mistake in the
> first place. On 64-bit kernels, there are no reasons we can't use PMD
> mappings for vmalloc. So I'd rather not go with this fix.
If you have strong preference for that approach, then we can go that way.
I don't like this patch that much anyway. The only upside is that it is
safer to backport, because it is obvious that it won't break anything else.
I will do some testing with PMD mapping on XIP, and come back later.
Best regards,
Nam