Re: linux-next: manual merge of the risc-v tree with Linus' tree

[Palmer Dabbelt]

On Tue, 30 Mar 2021 15:40:34 PDT (-0700), Stephen Rothwell wrote:
> Hi all,
>
> Today's linux-next merge of the risc-v tree got a conflict in:
>
>   arch/riscv/mm/kasan_init.c
>
> between commits:
>
>   f3773dd031de ("riscv: Ensure page table writes are flushed when initializing KASAN vmalloc")
>   78947bdfd752 ("RISC-V: kasan: Declare kasan_shallow_populate() static")
>
> from Linus' tree and commit:
>
>   2da073c19641 ("riscv: Cleanup KASAN_VMALLOC support")
>
> from the risc-v tree.
>
> I fixed it up (I think - see below) and can carry the fix as
> necessary. This is now fixed as far as linux-next is concerned, but any
> non trivial conflicts should be mentioned to your upstream maintainer
> when your tree is submitted for merging.  You may also want to consider
> cooperating with the maintainer of the conflicting tree to minimise any
> particularly complex conflicts.

They're my own trees ;)

I'm not so great at reading merge diffs, but the right fix here is to 
have the local_flush_tlb_all() after the call to 
kasan_shallow_populate_pgd(), just as there is one after 
kasan_populate_pgd().  My merge diff looks like this

diff --cc arch/riscv/mm/kasan_init.c
index 2c39f0386673,4f85c6d0ddf8..ec0029097251
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@@ -162,8 -159,36 +162,10 @@@ static void __init kasan_shallow_popula
 {
       unsigned long vaddr = (unsigned long)start & PAGE_MASK;
       unsigned long vend = PAGE_ALIGN((unsigned long)end);
-      unsigned long pfn;
-      int index;
-      void *p;
-      pud_t *pud_dir, *pud_k;
-      pgd_t *pgd_dir, *pgd_k;
-      p4d_t *p4d_dir, *p4d_k;
-
-      while (vaddr < vend) {
-              index = pgd_index(vaddr);
-              pfn = csr_read(CSR_SATP) & SATP_PPN;
-              pgd_dir = (pgd_t *)pfn_to_virt(pfn) + index;
-              pgd_k = init_mm.pgd + index;
-              pgd_dir = pgd_offset_k(vaddr);
-              set_pgd(pgd_dir, *pgd_k);
-
-              p4d_dir = p4d_offset(pgd_dir, vaddr);
-              p4d_k  = p4d_offset(pgd_k, vaddr);
-
-              vaddr = (vaddr + PUD_SIZE) & PUD_MASK;
-              pud_dir = pud_offset(p4d_dir, vaddr);
-              pud_k = pud_offset(p4d_k, vaddr);
-
-              if (pud_present(*pud_dir)) {
-                      p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
-                      pud_populate(&init_mm, pud_dir, p);
-              }
-              vaddr += PAGE_SIZE;
-      }
+
+      kasan_shallow_populate_pgd(vaddr, vend);
+
+       local_flush_tlb_all();
 }

 void __init kasan_init(void)

which doesn't include the diff to kasan_shallow_populate_pgd().  Not 
sure if that's just because my diff is in the other direction, though.  
The expected result is that kasan_shallow_populate_pgd() exists both pre 
and post merge.

> --
> Cheers,
> Stephen Rothwell
>
> diff --cc arch/riscv/mm/kasan_init.c
> index 4f85c6d0ddf8,2c39f0386673..000000000000
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@@ -153,44 -141,31 +141,33 @@@ static void __init kasan_populate(void 
>   
>   	local_flush_tlb_all();
>   	memset(start, KASAN_SHADOW_INIT, end - start);
>   }
>   
> + static void __init kasan_shallow_populate_pgd(unsigned long vaddr, unsigned long end)
> + {
> + 	unsigned long next;
> + 	void *p;
> + 	pgd_t *pgd_k = pgd_offset_k(vaddr);
> + 
> + 	do {
> + 		next = pgd_addr_end(vaddr, end);
> + 		if (pgd_page_vaddr(*pgd_k) == (unsigned long)lm_alias(kasan_early_shadow_pmd)) {
> + 			p = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> + 			set_pgd(pgd_k, pfn_pgd(PFN_DOWN(__pa(p)), PAGE_TABLE));
> + 		}
> + 	} while (pgd_k++, vaddr = next, vaddr != end);
> + }
> + 
>   static void __init kasan_shallow_populate(void *start, void *end)
>   {
>   	unsigned long vaddr = (unsigned long)start & PAGE_MASK;
>   	unsigned long vend = PAGE_ALIGN((unsigned long)end);
> - 	unsigned long pfn;
> - 	int index;
> - 	void *p;
> - 	pud_t *pud_dir, *pud_k;
> - 	pgd_t *pgd_dir, *pgd_k;
> - 	p4d_t *p4d_dir, *p4d_k;
> - 
> - 	while (vaddr < vend) {
> - 		index = pgd_index(vaddr);
> - 		pfn = csr_read(CSR_SATP) & SATP_PPN;
> - 		pgd_dir = (pgd_t *)pfn_to_virt(pfn) + index;
> - 		pgd_k = init_mm.pgd + index;
> - 		pgd_dir = pgd_offset_k(vaddr);
> - 		set_pgd(pgd_dir, *pgd_k);
> - 
> - 		p4d_dir = p4d_offset(pgd_dir, vaddr);
> - 		p4d_k  = p4d_offset(pgd_k, vaddr);
> - 
> - 		vaddr = (vaddr + PUD_SIZE) & PUD_MASK;
> - 		pud_dir = pud_offset(p4d_dir, vaddr);
> - 		pud_k = pud_offset(p4d_k, vaddr);
> - 
> - 		if (pud_present(*pud_dir)) {
> - 			p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> - 			pud_populate(&init_mm, pud_dir, p);
> - 		}
> - 		vaddr += PAGE_SIZE;
> - 	}
> + 
> + 	kasan_shallow_populate_pgd(vaddr, vend);
>  +
>  +	local_flush_tlb_all();
>   }
>   
>   void __init kasan_init(void)
>   {
>   	phys_addr_t _start, _end;