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From: Marcelo Tosatti on 16 Jul 2010 21:50
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(a)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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From: Avi Kivity on 18 Jul 2010 10:20
On 07/16/2010 05:13 AM, Lai Jiangshan wrote:
> add host_writable parameter for some functions,
> no functionality changed, prepare for using RO pages.
>
>

This simple patch really clarifies the code.

--

error compiling committee.c: too many arguments to function

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