Il 04/10/2013 15:38, Alexander Graf ha scritto:
>
> On 07.08.2013, at 12:03, Bharat Bhushan wrote:
>
>> When the MM code is invalidating a range of pages, it calls the KVM
>> kvm_mmu_notifier_invalidate_range_start() notifier function, which calls
>> kvm_unmap_hva_range(), which arranges to flush all the TLBs for guest pages.
>> However, the Linux PTEs for the range being flushed are still valid at
>> that point. We are not supposed to establish any new references to pages
>> in the range until the ...range_end() notifier gets called.
>> The PPC-specific KVM code doesn't get any explicit notification of that;
>> instead, we are supposed to use mmu_notifier_retry() to test whether we
>> are or have been inside a range flush notifier pair while we have been
>> referencing a page.
>>
>> This patch calls the mmu_notifier_retry() while mapping the guest
>> page to ensure we are not referencing a page when in range invalidation.
>>
>> This call is inside a region locked with kvm->mmu_lock, which is the
>> same lock that is called by the KVM MMU notifier functions, thus
>> ensuring that no new notification can proceed while we are in the
>> locked region.
>>
>> Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
>
> Acked-by: Alexander Graf <agraf@xxxxxxx>
>
> Gleb, Paolo, please queue for 3.12 directly.
Here is the backport. The second hunk has a nontrivial conflict, so
someone please give their {Tested,Reviewed,Compiled}-by.
Paolo
diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 1c6a9d7..c65593a 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -332,6 +332,13 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
unsigned long hva;
int pfnmap = 0;
int tsize = BOOK3E_PAGESZ_4K;
+ int ret = 0;
+ unsigned long mmu_seq;
+ struct kvm *kvm = vcpu_e500->vcpu.kvm;
+
+ /* used to check for invalidations in progress */
+ mmu_seq = kvm->mmu_notifier_seq;
+ smp_rmb();
/*
* Translate guest physical to true physical, acquiring
@@ -449,6 +456,12 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
gvaddr &= ~((tsize_pages << PAGE_SHIFT) - 1);
}
+ spin_lock(&kvm->mmu_lock);
+ if (mmu_notifier_retry(kvm, mmu_seq)) {
+ ret = -EAGAIN;
+ goto out;
+ }
+
kvmppc_e500_ref_setup(ref, gtlbe, pfn);
kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
@@ -457,10 +470,13 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
/* Clear i-cache for new pages */
kvmppc_mmu_flush_icache(pfn);
+out:
+ spin_unlock(&kvm->mmu_lock);
+
/* Drop refcount on page, so that mmu notifiers can clear it */
kvm_release_pfn_clean(pfn);
- return 0;
+ return ret;
}
/* XXX only map the one-one case, for now use TLB0 */
--
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