Re: [PATCH 3/5] mmu: don't set the present bit unconditionally

From	Xiao Guangrong <guangrong.xiao@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/5] mmu: don't set the present bit unconditionally
Date	2016-06-29 05:30 +0200
Message-ID	<rPemm-7iT-5@gated-at.bofh.it> (permalink)
References	<rOSYx-1Xl-7@gated-at.bofh.it> <rOSYx-1Xl-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 06/28/2016 12:32 PM, Bandan Das wrote:
> To support execute only mappings on behalf of L1
> hypervisors, we teach set_spte() to honor L1's valid XWR
> bits. This is only if host supports EPT execute only. Reuse
> ACC_USER_MASK to signify if the L1 hypervisor has the R bit
> set
>
> Signed-off-by: Bandan Das <bsd@redhat.com>
> ---
>   arch/x86/kvm/mmu.c         | 9 +++++++--
>   arch/x86/kvm/paging_tmpl.h | 2 +-
>   arch/x86/kvm/vmx.c         | 2 +-
>   3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 875d4f7..ee2fb16 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2516,13 +2516,17 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>   		    gfn_t gfn, kvm_pfn_t pfn, bool speculative,
>   		    bool can_unsync, bool host_writable)
>   {
> -	u64 spte;
> +	u64 spte = 0;
>   	int ret = 0;
> +	struct kvm_mmu *context = &vcpu->arch.mmu;
> +	bool execonly = !(context->guest_rsvd_check.bad_mt_xwr &
> +			  (1ull << VMX_EPT_EXECUTABLE_MASK));

Could we introduce a new field, say execonly, to "struct kvm_mmu"?
That would make the code be more clearer.

Thread

[PATCH 3/5] mmu: don't set the present bit unconditionally Bandan Das <bsd@redhat.com> - 2016-06-28 06:40 +0200
  Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Paolo Bonzini <pbonzini@redhat.com> - 2016-06-28 11:00 +0200
    Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Bandan Das <bsd@redhat.com> - 2016-06-28 19:50 +0200
      Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Paolo Bonzini <pbonzini@redhat.com> - 2016-06-28 22:30 +0200
    Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Wanpeng Li <kernellwp@gmail.com> - 2016-07-05 08:00 +0200
      Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Paolo Bonzini <pbonzini@redhat.com> - 2016-07-05 13:00 +0200
  Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-06-29 05:30 +0200
    Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Paolo Bonzini <pbonzini@redhat.com> - 2016-06-29 10:20 +0200
      Re: [PATCH 3/5] mmu: don't set the present bit unconditionally Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-06-30 09:30 +0200

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