From 05f2bb0313a2855e491dadfc8319b7da261d7074 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@ozlabs.org>
Date: Wed, 7 Feb 2018 19:49:54 +1100
Subject: [PATCH] KVM: PPC: Book3S HV: Fix handling of secondary HPTEG in HPT
resizing code
References: bsc#1061840
Patch-mainline: v4.16-rc1
Git-commit: 05f2bb0313a2855e491dadfc8319b7da261d7074
This fixes the computation of the HPTE index to use when the HPT
resizing code encounters a bolted HPTE which is stored in its
secondary HPTE group. The code inverts the HPTE group number, which
is correct, but doesn't then mask it with new_hash_mask. As a result,
new_pteg will be effectively negative, resulting in new_hptep
pointing before the new HPT, which will corrupt memory.
In addition, this removes two BUG_ON statements. The condition that
the BUG_ONs were testing -- that we have computed the hash value
incorrectly -- has never been observed in testing, and if it did
occur, would only affect the guest, not the host. Given that
BUG_ON should only be used in conditions where the kernel (i.e.
the host kernel, in this case) can't possibly continue execution,
it is not appropriate here.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 966097232d21..d19649960bbf 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1329,12 +1329,8 @@ static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize,
}
new_pteg = hash & new_hash_mask;
- if (vpte & HPTE_V_SECONDARY) {
- BUG_ON(~pteg != (hash & old_hash_mask));
- new_pteg = ~new_pteg;
- } else {
- BUG_ON(pteg != (hash & old_hash_mask));
- }
+ if (vpte & HPTE_V_SECONDARY)
+ new_pteg = ~hash & new_hash_mask;
new_idx = new_pteg * HPTES_PER_GROUP + (idx % HPTES_PER_GROUP);
new_hptep = (__be64 *)(new->virt + (new_idx << 4));
--
2.13.7