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Commit 05f2bb03 authored by Paul Mackerras's avatar Paul Mackerras
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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: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent 57ea5f16

arch/powerpc/kvm/book3s_64_mmu_hv.c

+2 −6
Original line number Original line Diff line number Diff line
@@ -1329,12 +1329,8 @@ static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize, 
	}

	}





	new_pteg = hash & new_hash_mask;

	new_pteg = hash & new_hash_mask;

	if (vpte & HPTE_V_SECONDARY) {

	if (vpte & HPTE_V_SECONDARY)

		BUG_ON(~pteg != (hash & old_hash_mask));

		new_pteg = ~hash & new_hash_mask;

		new_pteg = ~new_pteg;

	} else {

		BUG_ON(pteg != (hash & old_hash_mask));

	}





	new_idx = new_pteg * HPTES_PER_GROUP + (idx % HPTES_PER_GROUP);

	new_idx = new_pteg * HPTES_PER_GROUP + (idx % HPTES_PER_GROUP);

	new_hptep = (__be64 *)(new->virt + (new_idx << 4));

	new_hptep = (__be64 *)(new->virt + (new_idx << 4));