Re: Linux-next-20200302: arm64 build failed

Catalin Marinas
2020-03-02T17:45:58Z

On Mon, Mar 02, 2020 at 03:54:43PM +0200, Mike Rapoport wrote:
> On Mon, Mar 02, 2020 at 10:47:27AM +0000, Will Deacon wrote:
> > [+Anshuman and Catalin]
> >
> > On Mon, Mar 02, 2020 at 01:58:26PM +0530, Naresh Kamboju wrote:
> > > Linux-Next 20200302 arm64 build failed due to below errors,
> > > Suspecting patch causing this build break.
> > >
> > > 87d900aef3e2 arm/arm64: add support for folded p4d page tables
> > >
> > > Error log,
> > > -------------
> > > arch/arm64/mm/mmu.c: In function 'unmap_hotplug_pud_range':
> > > include/linux/compiler.h:284:1: error: incompatible type for argument
> > > 1 of 'p4d_page_paddr'
> > > ({ \
> > > ^
> > > arch/arm64/include/asm/memory.h:270:45: note: in definition of macro
> > > '__phys_to_virt'
> > > #define __phys_to_virt(x) ((unsigned long)((x) - physvirt_offset))
> > > ^
> > > arch/arm64/include/asm/pgtable.h:629:42: note: in expansion of macro '__va'
> > > #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
> > > ^~~~
> > > include/linux/compiler.h:293:22: note: in expansion of macro '__READ_ONCE'
> > > #define READ_ONCE(x) __READ_ONCE(x, 1)
> > > ^~~~~~~~~~~
> > > arch/arm64/include/asm/pgtable.h:628:52: note: in expansion of macro 'READ_ONCE'
> > > #define pud_offset_phys(dir, addr) (p4d_page_paddr(READ_ONCE(*(dir)))
> > > + pud_index(addr) * sizeof(pud_t))
> > > ^~~~~~~~~
> > > arch/arm64/include/asm/pgtable.h:629:47: note: in expansion of macro
> > > 'pud_offset_phys'
> > > #define pud_offset(dir, addr) ((pud_t *)__va(pud_offset_phys((dir), (addr))))
> > > ^~~~~~~~~~~~~~~
> > > arch/arm64/mm/mmu.c:827:10: note: in expansion of macro 'pud_offset'
> > > pudp = pud_offset(pgdp, addr);
> > > ^~~~~~~~~~
> >
> > Looks like we need an implementation of unmap_hotplug_p4d_range() to
> > walk the dummy p4d level. Unfortunately, we don't have the folded p4d
> > patches in the arm64 tree so we'll either need a common branch or the
> > hotplug patches will need to be dropped for the moment.
>
> unmap_hotplug_p4d_range() is easy :)
>
> From c7a5d08ff51ca2057b6b0289c4423bdfd7643518 Mon Sep 17 00:00:00 2001
> From: Mike Rapoport <rppt@linux.ibm.com>
> Date: Mon, 2 Mar 2020 15:53:17 +0200
> Subject: [PATCH] arm64/mm: implement unmap_hotplug_p4d_range
>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
> arch/arm64/mm/mmu.c | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 05ec8e5f1436..c76b11577558 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -840,6 +840,24 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
> } while (addr = next, addr < end);
> }
>
> +static void unmap_hotplug_p4d_range(pgd_t *pgd, unsigned long addr,
> + unsigned long end, bool free_mapped)
> +{
> + unsigned long next;
> + pgd_t *p4dp, p4d;
> +
> + do {
> + next = p4d_addr_end(addr, end);
> + p4dp = p4d_offset(pgd, addr);
> + p4d = READ_ONCE(*p4dp);
> + if (p4d_none(p4d))
> + continue;
> +
> + WARN_ON(!p4d_present(p4d));
> + unmap_hotplug_pud_range(p4dp, addr, next, free_mapped);
> + } while (addr = next, addr < end);
> +}
> +
> static void unmap_hotplug_range(unsigned long addr, unsigned long end,
> bool free_mapped)
> {
> @@ -854,7 +872,7 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
> continue;
>
> WARN_ON(!pgd_present(pgd));
> - unmap_hotplug_pud_range(pgdp, addr, next, free_mapped);
> + unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped);
> } while (addr = next, addr < end);
> }

Thanks Mike. With the additional diff below, I can get it to build with
and without the p4d clean-up patches in -next. If Anshuman confirms that
they work, I can add them on top of the arm64 for-next/memory-hotremove
branch

----------8<------------------------
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 56bd9227937f..2faf11860097 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -816,7 +816,7 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
} while (addr = next, addr < end);
}

-static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
+static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
unsigned long end, bool free_mapped)
{
unsigned long next;
@@ -824,7 +824,7 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,

do {
next = pud_addr_end(addr, end);
- pudp = pud_offset(pgdp, addr);
+ pudp = pud_offset(p4dp, addr);
pud = READ_ONCE(*pudp);
if (pud_none(pud))
continue;
@@ -848,15 +848,15 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
} while (addr = next, addr < end);
}

-static void unmap_hotplug_p4d_range(pgd_t *pgd, unsigned long addr,
- unsigned long end, bool free_mapped)
+static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
+ unsigned long end, bool free_mapped)
{
unsigned long next;
- pgd_t *p4dp, p4d;
+ p4d_t *p4dp, p4d;

do {
next = p4d_addr_end(addr, end);
- p4dp = p4d_offset(pgd, addr);
+ p4dp = p4d_offset(pgdp, addr);
p4d = READ_ONCE(*p4dp);
if (p4d_none(p4d))
continue;
@@ -961,7 +961,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
free_hotplug_pgtable_page(virt_to_page(pmdp));
}

-static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,
+static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
unsigned long end, unsigned long floor,
unsigned long ceiling)
{
@@ -970,7 +970,7 @@ static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,

do {
next = pud_addr_end(addr, end);
- pudp = pud_offset(pgdp, addr);
+ pudp = pud_offset(p4dp, addr);
pud = READ_ONCE(*pudp);
if (pud_none(pud))
continue;
@@ -990,17 +990,36 @@ static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,
* entries are empty. Overlap with other regions have been
* handled by the floor/ceiling check.
*/
- pudp = pud_offset(pgdp, 0UL);
+ pudp = pud_offset(p4dp, 0UL);
for (i = 0; i < PTRS_PER_PUD; i++) {
if (!pud_none(READ_ONCE(pudp[i])))
return;
}

- pgd_clear(pgdp);
+ p4d_clear(p4dp);
__flush_tlb_kernel_pgtable(start);
free_hotplug_pgtable_page(virt_to_page(pudp));
}

+static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
+ unsigned long end, unsigned long floor,
+ unsigned long ceiling)
+{
+ p4d_t *p4dp, p4d;
+ unsigned long next;
+
+ do {
+ next = p4d_addr_end(addr, end);
+ p4dp = p4d_offset(pgdp, addr);
+ p4d = READ_ONCE(*p4dp);
+ if (p4d_none(p4d))
+ continue;
+
+ WARN_ON(!p4d_present(p4d));
+ free_empty_pud_table(p4dp, addr, next, floor, ceiling);
+ } while (addr = next, addr < end);
+}
+
static void free_empty_tables(unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
@@ -1015,7 +1034,7 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
continue;

WARN_ON(!pgd_present(pgd));
- free_empty_pud_table(pgdp, addr, next, floor, ceiling);
+ free_empty_p4d_table(pgdp, addr, next, floor, ceiling);
} while (addr = next, addr < end);
}
#endif