[PATCH] kvm: ppc: stop leaking host memory on VM exit

[PATCH] kvm: ppc: stop leaking host memory on VM exit

[Hollis Blanchard]

When the VM exits, we must call put_page() for every page referenced in the
shadow TLB.

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB
pages). The maximum number of pages leaked is the size of our shadow TLB, 64
pages.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
---
The obvious question is "why didn't we see this before?" Basically, we'd never
looked for it, and since most of our work was in the kernel we always ended up
rebooting before exhausting host memory.

Since it's such a large leak, and a simple fix, please commit this for 2.6.28.
This patch does apply to kvm.git with fuzz, but if you prefer I can send a
separate patch for that later.

diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -104,4 +104,6 @@ static inline void kvmppc_set_pid(struct
 	}
 }
 
+extern void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu);
+
 #endif /* __POWERPC_KVM_PPC_H__ */
diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
--- a/arch/powerpc/kvm/44x_tlb.c
+++ b/arch/powerpc/kvm/44x_tlb.c
@@ -124,6 +124,14 @@ static void kvmppc_44x_shadow_release(st
 	}
 }
 
+void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu)
+{
+	int i;
+
+	for (i = 0; i <= tlb_44x_hwater; i++)
+		kvmppc_44x_shadow_release(vcpu, i);
+}
+
 void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
 {
     vcpu->arch.shadow_tlb_mod[i] = 1;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -238,6 +238,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *
 
 void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
+	kvmppc_core_destroy_mmu(vcpu);
 }
 
 /* Note: clearing MSR[DE] just means that the debug interrupt will not be

-- 
Hollis Blanchard
IBM Linux Technology Center

RE: [PATCH] kvm: ppc: stop leaking host memory on VM exit

[Liu Yu]

Good catch.
 
> -----Original Message-----
> From: kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org 
> [mailto:kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Hollis Blanchard
> Sent: Tuesday, November 25, 2008 1:38 AM
> To: Avi Kivity
> Cc: kvm-ppc; kvm
> Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit
> 
> When the VM exits, we must call put_page() for every page 
> referenced in the
> shadow TLB.
> 
> Without this patch, we usually leak 30-50 host pages (120 - 
> 200 KiB with 4 KiB
> pages). The maximum number of pages leaked is the size of our 
> shadow TLB, 64
> pages.
> 
> Signed-off-by: Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> ---
> The obvious question is "why didn't we see this before?" 
> Basically, we'd never
> looked for it, and since most of our work was in the kernel 
> we always ended up
> rebooting before exhausting host memory.
> 
> Since it's such a large leak, and a simple fix, please commit 
> this for 2.6.28.
> This patch does apply to kvm.git with fuzz, but if you prefer 
> I can send a
> separate patch for that later.
> 
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RE: [PATCH] kvm: ppc: stop leaking host memory on VM exit

[Liu Yu]

> -----Original Message-----
> From: kvm-ppc-owner@vger.kernel.org 
> [mailto:kvm-ppc-owner@vger.kernel.org] On Behalf Of Hollis Blanchard
> Sent: Tuesday, November 25, 2008 1:38 AM
> To: Avi Kivity
> Cc: kvm-ppc; kvm
> Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit
> 
> When the VM exits, we must call put_page() for every page 
> referenced in the
> shadow TLB.
> 
> Without this patch, we usually leak 30-50 host pages (120 - 
> 200 KiB with 4 KiB
> pages). The maximum number of pages leaked is the size of our 
> shadow TLB, 64
> pages.
> 
> Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>

Need it also to _tlbia() at vcpu_uninit?

Re: [PATCH] kvm: ppc: stop leaking host memory on VM exit

[Avi Kivity]

Hollis Blanchard wrote:
> When the VM exits, we must call put_page() for every page referenced in the
> shadow TLB.
>
> Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB
> pages). The maximum number of pages leaked is the size of our shadow TLB, 64
> pages.
>
> Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
> ---
> The obvious question is "why didn't we see this before?" Basically, we'd never
> looked for it, and since most of our work was in the kernel we always ended up
> rebooting before exhausting host memory.
>
> Since it's such a large leak, and a simple fix, please commit this for 2.6.28.
> This patch does apply to kvm.git with fuzz, but if you prefer I can send a
> separate patch for that later.
>   

Applied on both master and the 2.6.28 queue.


-- 
error compiling committee.c: too many arguments to function

RE: [PATCH] kvm: ppc: stop leaking host memory on VM exit

[Hollis Blanchard]

On Tue, 2008-11-25 at 16:32 +0800, Liu Yu wrote:
> > -----Original Message-----
> > From: kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org 
> > [mailto:kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Hollis Blanchard
> > Sent: Tuesday, November 25, 2008 1:38 AM
> > To: Avi Kivity
> > Cc: kvm-ppc; kvm
> > Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit
> > 
> > When the VM exits, we must call put_page() for every page 
> > referenced in the
> > shadow TLB.
> > 
> > Without this patch, we usually leak 30-50 host pages (120 - 
> > 200 KiB with 4 KiB
> > pages). The maximum number of pages leaked is the size of our 
> > shadow TLB, 64
> > pages.
> > 
> > Signed-off-by: Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
> Need it also to _tlbia() at vcpu_uninit?

No, because by the time we hit kvm_arch_vcpu_uninit(),
kvm_arch_vcpu_put() has already been called.

-- 
Hollis Blanchard
IBM Linux Technology Center

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