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

[Christophe Leroy]

Nicholas Piggin <npig...@gmail.com> a écrit :

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 <npig...@gmail.com>
---
 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);

Looks strange, before we have ~MASK now we have mask without the ~

Also use PFN_PHYS() instead of open coding ?

+
        return __va(addr);
 }

--
2.23.0