Subject: Re: Linux-next-20200302: arm64 build failed

From: Catalin Marinas <[email-masked]>
Date: Mon, 2 Mar 2020 17:45:53 +0000

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 <[email-masked]>
> Date: Mon, 2 Mar 2020 15:53:17 +0200
> Subject: [PATCH] arm64/mm: implement unmap_hotplug_p4d_range
> 
> Signed-off-by: Mike Rapoport <[email-masked]>
> ---
>  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