LinuxLists.cc - [PATCH 0/2] kvm: fix a bug and remove a redundancy in async

2013-09-04 20:34:16

Subject: [PATCH 0/2] kvm: fix a bug and remove a redundancy in async_pf

I did not reproduce the bug fixed in [1/2], but there are not that many
reasons why we could not unload a module, so the spot is quite obvious.

Radim Krčmář (2):
kvm: free resources after canceling async_pf
kvm: remove .done from struct kvm_async_pf

include/linux/kvm_host.h | 1 -
virt/kvm/async_pf.c | 8 ++++----
2 files changed, 4 insertions(+), 5 deletions(-)

--
1.8.3.1

2013-09-04 20:34:14

by Radim Krčmář

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Subject: [PATCH 1/2] kvm: free resources after canceling async_pf

When we cancel 'async_pf_execute()', we should behave as if the work was
never scheduled in 'kvm_setup_async_pf()'.
Fixes a bug when we can't unload module because the vm wasn't destroyed.

Signed-off-by: Radim Krčmář <[email protected]>
---
virt/kvm/async_pf.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index b44cea0..f30aa1c 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -102,8 +102,11 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
typeof(*work), queue);
cancel_work_sync(&work->work);
list_del(&work->queue);
- if (!work->done) /* work was canceled */
+ if (!work->done) { /* work was canceled */
+ mmdrop(work->mm);
+ kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
kmem_cache_free(async_pf_cache, work);
+ }
}

spin_lock(&vcpu->async_pf.lock);
--
1.8.3.1

2013-09-04 20:34:13

by Radim Krčmář

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Subject: [PATCH 2/2] kvm: remove .done from struct kvm_async_pf

'.done' is used to mark the completion of 'async_pf_execute()', but
'cancel_work_sync()' returns true when the work was canceled, so we
use it instead.

Signed-off-by: Radim Krčmář <[email protected]>
---
include/linux/kvm_host.h | 1 -
virt/kvm/async_pf.c | 5 +----
2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ca645a0..c7a5e08 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -190,7 +190,6 @@ struct kvm_async_pf {
unsigned long addr;
struct kvm_arch_async_pf arch;
struct page *page;
- bool done;
};

void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index f30aa1c..89acf41 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -76,7 +76,6 @@ static void async_pf_execute(struct work_struct *work)
spin_lock(&vcpu->async_pf.lock);
list_add_tail(&apf->link, &vcpu->async_pf.done);
apf->page = page;
- apf->done = true;
spin_unlock(&vcpu->async_pf.lock);

/*
@@ -100,9 +99,8 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
struct kvm_async_pf *work =
list_entry(vcpu->async_pf.queue.next,
typeof(*work), queue);
- cancel_work_sync(&work->work);
list_del(&work->queue);
- if (!work->done) { /* work was canceled */
+ if (cancel_work_sync(&work->work)) {
mmdrop(work->mm);
kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */
kmem_cache_free(async_pf_cache, work);
@@ -167,7 +165,6 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
return 0;

work->page = NULL;
- work->done = false;
work->vcpu = vcpu;
work->gva = gva;
work->addr = gfn_to_hva(vcpu->kvm, gfn);
--
1.8.3.1

2013-09-05 15:52:51

by Paolo Bonzini

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Subject: Re: [PATCH 0/2] kvm: fix a bug and remove a redundancy in async_pf

Il 04/09/2013 22:32, Radim Krčmář ha scritto:
> I did not reproduce the bug fixed in [1/2], but there are not that many
> reasons why we could not unload a module, so the spot is quite obvious.
>
>
> Radim Krčmář (2):
> kvm: free resources after canceling async_pf
> kvm: remove .done from struct kvm_async_pf
>
> include/linux/kvm_host.h | 1 -
> virt/kvm/async_pf.c | 8 ++++----
> 2 files changed, 4 insertions(+), 5 deletions(-)
>

Reviewed-by: Paolo Bonzini <[email protected]>

2013-09-08 08:34:01

by Gleb Natapov

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Subject: Re: [PATCH 0/2] kvm: fix a bug and remove a redundancy in async_pf

On Wed, Sep 04, 2013 at 10:32:22PM +0200, Radim Krčmář wrote:
> I did not reproduce the bug fixed in [1/2], but there are not that many
> reasons why we could not unload a module, so the spot is quite obvious.
>
>
Reviewed-by: Gleb Natapov <[email protected]>

> Radim Krčmář (2):
> kvm: free resources after canceling async_pf
> kvm: remove .done from struct kvm_async_pf
>
> include/linux/kvm_host.h | 1 -
> virt/kvm/async_pf.c | 8 ++++----
> 2 files changed, 4 insertions(+), 5 deletions(-)
>
> --
> 1.8.3.1

--
Gleb.

2013-09-12 16:32:53

by Paolo Bonzini

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