Messages in this thread | | | Date | Fri, 16 Jul 2010 20:18:55 -0300 | From | Marcelo Tosatti <> | Subject | Re: [PATCH 4/6] kvm: add host_writable parameter |
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On Fri, Jul 16, 2010 at 10:13:04AM +0800, Lai Jiangshan wrote: > add host_writable parameter for some functions, > no functionality changed, prepare for using RO pages. > > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > --- > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 0867ced..8ba9b0d 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -1861,7 +1861,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, > unsigned pte_access, int user_fault, > int write_fault, int dirty, int level, > gfn_t gfn, pfn_t pfn, bool speculative, > - bool can_unsync, bool reset_host_protection) > + bool can_unsync, bool host_writable) > { > u64 spte; > int ret = 0; > @@ -1888,8 +1888,10 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, > spte |= kvm_x86_ops->get_mt_mask(vcpu, gfn, > kvm_is_mmio_pfn(pfn)); > > - if (reset_host_protection) > + if (host_writable) > spte |= SPTE_HOST_WRITEABLE; > + else > + pte_access &= ~ACC_WRITE_MASK;
Two vcpus faulting the same address with different access type can now race:
vcpu0 vcpu1
read fault write fault gfn_to_pfn readonly gfn_to_pfn write, break COW set writable spte to COWed page vcpu writes to page set spte to original page vcpu reads stale content
Should not instantiate a new spte if (pfn != spte_to_pfn(*sptep)), to cause a refault.
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