KVM guests freeze under upstream kernel

[Michael Ellerman]

Suraj Jitindar Singh <sjitindarsingh at gmail.com> writes:
>
...
> kernel BUG at /scratch/surajjs/linux/arch/powerpc/include/asm/book3s/64/radix.h:260!

Next thing to try would be something like below.

cheers

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index d1da415e283c..c749a757738e 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1016,6 +1016,7 @@ static inline unsigned long
 pmd_hugepage_update(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp,
 		    unsigned long clr, unsigned long set)
 {
+	BUG_ON(set & PAGE_DEVMAP);
 	if (radix_enabled())
 		return radix__pmd_hugepage_update(mm, addr, pmdp, clr, set);
 	return hash__pmd_hugepage_update(mm, addr, pmdp, clr, set);
diff --git a/arch/powerpc/mm/pgtable-book3s64.c b/arch/powerpc/mm/pgtable-book3s64.c
index 31eed8fa8e99..55c443a3dd5b 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/arch/powerpc/mm/pgtable-book3s64.c
@@ -31,6 +31,7 @@ int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
 			  pmd_t *pmdp, pmd_t entry, int dirty)
 {
 	int changed;
+	BUG_ON(pmd & PAGE_DEVMAP);
 #ifdef CONFIG_DEBUG_VM
 	WARN_ON(!pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
 	assert_spin_locked(&vma->vm_mm->page_table_lock);
@@ -56,6 +57,7 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 		pmd_t *pmdp, pmd_t pmd)
 {
+	BUG_ON(pmd & PAGE_DEVMAP);
 #ifdef CONFIG_DEBUG_VM
 	WARN_ON(pte_present(pmd_pte(*pmdp)) && !pte_protnone(pmd_pte(*pmdp)));
 	assert_spin_locked(&mm->page_table_lock);