* [PATCH V2] PPC: Fix race in mtmsr paravirt implementation
@ 2011-10-13 9:59 Bharat Bhushan
2011-10-13 10:11 ` Alexander Graf
0 siblings, 1 reply; 3+ messages in thread
From: Bharat Bhushan @ 2011-10-13 9:59 UTC (permalink / raw)
To: kvm-ppc
The current implementation of mtmsr and mtmsrd are racy in that it does:
* check (int_pending = 0)
---> host sets int_pending = 1 <---
* write shared page
* done
while instead we should check for int_pending after the shared page is written.
Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v2:
- msr.ee and int_pending are checked as earlier.
arch/powerpc/kernel/kvm_emul.S | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/kvm_emul.S b/arch/powerpc/kernel/kvm_emul.S
index f2b1b25..3d64c57 100644
--- a/arch/powerpc/kernel/kvm_emul.S
+++ b/arch/powerpc/kernel/kvm_emul.S
@@ -167,6 +167,9 @@ maybe_stay_in_guest:
kvm_emulate_mtmsr_reg2:
ori r30, r0, 0
+ /* Put MSR into magic page because we don't call mtmsr */
+ STL64(r30, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)
+
/* Check if we have to fetch an interrupt */
lwz r31, (KVM_MAGIC_PAGE + KVM_MAGIC_INT)(0)
cmpwi r31, 0
@@ -174,15 +177,10 @@ kvm_emulate_mtmsr_reg2:
/* Check if we may trigger an interrupt */
andi. r31, r30, MSR_EE
- beq no_mtmsr
-
- b do_mtmsr
+ bne do_mtmsr
no_mtmsr:
- /* Put MSR into magic page because we don't call mtmsr */
- STL64(r30, KVM_MAGIC_PAGE + KVM_MAGIC_MSR, 0)
-
SCRATCH_RESTORE
/* Go back to caller */
--
1.7.0.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V2] PPC: Fix race in mtmsr paravirt implementation
2011-10-13 9:59 [PATCH V2] PPC: Fix race in mtmsr paravirt implementation Bharat Bhushan
@ 2011-10-13 10:11 ` Alexander Graf
0 siblings, 0 replies; 3+ messages in thread
From: Alexander Graf @ 2011-10-13 10:11 UTC (permalink / raw)
To: Bharat Bhushan
Cc: kvm-ppc, bharatb.yadav, Bharat Bhushan, kvm@vger.kernel.org
On 10/13/2011 11:47 AM, Bharat Bhushan wrote:
> The current implementation of mtmsr and mtmsrd are racy in that it does:
>
> * check (int_pending = 0)
> ---> host sets int_pending = 1<---
> * write shared page
> * done
>
> while instead we should check for int_pending after the shared page is written.
>
> Signed-off-by: Bharat Bhushan<bharat.bhushan@freescale.com>
Thanks, applied to kvm-ppc-next.
Alex
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH V2] PPC: Fix race in mtmsr paravirt implementation
@ 2011-10-13 10:11 ` Alexander Graf
0 siblings, 0 replies; 3+ messages in thread
From: Alexander Graf @ 2011-10-13 10:11 UTC (permalink / raw)
To: Bharat Bhushan
Cc: kvm-ppc, bharatb.yadav, Bharat Bhushan, kvm@vger.kernel.org
On 10/13/2011 11:47 AM, Bharat Bhushan wrote:
> The current implementation of mtmsr and mtmsrd are racy in that it does:
>
> * check (int_pending == 0)
> ---> host sets int_pending = 1<---
> * write shared page
> * done
>
> while instead we should check for int_pending after the shared page is written.
>
> Signed-off-by: Bharat Bhushan<bharat.bhushan@freescale.com>
Thanks, applied to kvm-ppc-next.
Alex
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-10-13 9:59 [PATCH V2] PPC: Fix race in mtmsr paravirt implementation Bharat Bhushan
2011-10-13 10:11 ` Alexander Graf
2011-10-13 10:11 ` Alexander Graf
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