From 586b7ccdb7143b6a9b975d2c6ad52b6ca5c162b9 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Tue, 28 Jul 2015 15:03:05 +0200
Subject: [PATCH 1/2] KVM: s390: Fix hang VCPU hang/loop regression
commit 785dbef407d8 ("KVM: s390: optimize round trip time in request
handling") introduced a regression. This regression was seen with
CPU hotplug in the guest and switching between 1 or 2 CPUs. This will
set/reset the IBS control via synced request.
Whenever we make a synced request, we first set the vcpu->requests
bit and then block the vcpu. The handler, on the other hand, unblocks
itself, processes vcpu->requests (by clearing them) and unblocks itself
once again.
Now, if the requester sleeps between setting of vcpu->requests and
blocking, the handler will clear the vcpu->requests bit and try to
unblock itself (although no bit is set). When the requester wakes up,
it blocks the VCPU and we have a blocked VCPU without requests.
Solution is to always unset the block bit.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Fixes: 785dbef407d8 ("KVM: s390: optimize round trip time in request handling")
---
arch/s390/kvm/kvm-s390.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 2078f92d15ac..f32f843a3631 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1742,10 +1742,10 @@ static bool ibs_enabled(struct kvm_vcpu *vcpu)
static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
{
- if (!vcpu->requests)
- return 0;
retry:
kvm_s390_vcpu_request_handled(vcpu);
+ if (!vcpu->requests)
+ return 0;
/*
* We use MMU_RELOAD just to re-arm the ipte notifier for the
* guest prefix page. gmap_ipte_notify will wait on the ptl lock.
From fc1a8126bf8095b10f5a79893f2d2b19227f88f2 Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Tue, 4 Aug 2015 10:58:26 -0600
Subject: [PATCH 2/2] KVM: MTRR: Use default type for non-MTRR-covered gfn
before WARN_ON
The patch was munged on commit to re-order these tests resulting in
excessive warnings when trying to do device assignment. Return to
original ordering: https://lkml.org/lkml/2015/7/15/769
Fixes: 3e5d2fdceda1 ("KVM: MTRR: simplify kvm_mtrr_get_guest_memory_type")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/mtrr.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index dc0a84a6f309..9e8bf13572e6 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -672,16 +672,16 @@ u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
if (iter.mtrr_disabled)
return mtrr_disabled_type();
+ /* not contained in any MTRRs. */
+ if (type == -1)
+ return mtrr_default_type(mtrr_state);
+
/*
* We just check one page, partially covered by MTRRs is
* impossible.
*/
WARN_ON(iter.partial_map);
- /* not contained in any MTRRs. */
- if (type == -1)
- return mtrr_default_type(mtrr_state);
-
return type;
}
EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);