Subject: [PATCH] KVM: PPC: Book3S HV: Fix reverse map real-mode address lookup with huge vmalloc

From: Nicholas Piggin <[email-masked]>
Date: Mon, 24 May 2021 01:53:38 +1000

real_vmalloc_addr() does not currently work for huge vmalloc, which is
what the reverse map can be allocated with for radix host, hash guest.

Add huge page awareness to the function.

Fixes: 8abddd968a30 ("powerpc/64s/radix: Enable huge vmalloc mappings")
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kvm/book3s_hv_rm_mmu.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 7af7c70f1468..5f68cb5cc009 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -26,16 +26,23 @@
 static void *real_vmalloc_addr(void *x)
 {
 	unsigned long addr = (unsigned long) x;
+	unsigned long mask;
+	int shift;
 	pte_t *p;
+
 	/*
-	 * assume we don't have huge pages in vmalloc space...
-	 * So don't worry about THP collapse/split. Called
-	 * Only in realmode with MSR_EE = 0, hence won't need irq_save/restore.
+	 * This is called only in realmode with MSR_EE = 0, hence won't need
+	 * irq_save/restore around find_init_mm_pte.
 	 */
-	p = find_init_mm_pte(addr, NULL);
+	p = find_init_mm_pte(addr, &shift);
 	if (!p || !pte_present(*p))
 		return NULL;
-	addr = (pte_pfn(*p) << PAGE_SHIFT) | (addr & ~PAGE_MASK);
+	if (!shift)
+		shift = PAGE_SHIFT;
+
+	mask = (1UL << shift) - 1;
+	addr = (pte_pfn(*p) << PAGE_SHIFT) | (addr & mask);
+
 	return __va(addr);
 }
 
-- 
2.23.0