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KVM: PPC: Book3S HV: Fix handling of secondary HPTEG in HPT resizing code 

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>
This commit is contained in:
Paul Mackerras 2018-02-07 19:49:54 +11:00
parent 57ea5f161a
commit 05f2bb0313
1 changed files with 2 additions and 6 deletions
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8
arch/powerpc/kvm/book3s_64_mmu_hv.c
View File

@ -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));