Patchwork KVM: PPC: Book3S HV: Fix bug leading to deadlock in guest HPT updates

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Submitter Paul Mackerras
Date May 10, 2012, 9:49 a.m.
Message ID <20120510094924.GA16271@bloggs.ozlabs.ibm.com>
Download mbox | patch
Permalink /patch/158236/
State New
Headers show

Comments

Paul Mackerras - May 10, 2012, 9:49 a.m.
When handling the H_BULK_REMOVE hypercall, we were forgetting to
invalidate and unlock the hashed page table entry (HPTE) in the case
where the page had been paged out.  This fixes it by clearing the
first doubleword of the HPTE in that case.

This fixes a regression introduced in commit a92bce95f0 ("KVM: PPC:
Book3S HV: Keep HPTE locked when invalidating").  The effect of the
regression is that the host kernel will sometimes hang when under
memory pressure.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_hv_rm_mmu.c |    1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index def880a..cec4dad 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -463,6 +463,7 @@  long kvmppc_h_bulk_remove(struct kvm_vcpu *vcpu)
 				/* insert R and C bits from PTE */
 				rcbits = rev->guest_rpte & (HPTE_R_R|HPTE_R_C);
 				args[j] |= rcbits << (56 - 5);
+				hp[0] = 0;
 				continue;
 			}