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

From	Wanpeng Li <kernellwp@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/5] mmu: don't set the present bit unconditionally
Date	2016-07-05 08:00 +0200
Message-ID	<rRryN-79U-13@gated-at.bofh.it> (permalink)
References	<rOSYx-1Xl-7@gated-at.bofh.it> <rOSYx-1Xl-9@gated-at.bofh.it> <rOX2a-4Ab-35@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

2016-06-28 16:57 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 28/06/2016 06:32, Bandan Das wrote:
>> +     bool execonly = !(context->guest_rsvd_check.bad_mt_xwr &
>> +                       (1ull << VMX_EPT_EXECUTABLE_MASK));
>>
>>       if (set_mmio_spte(vcpu, sptep, gfn, pfn, pte_access))
>>               return 0;
>>
>> -     spte = PT_PRESENT_MASK;
>> +     if (!execonly)
>> +             spte |= PT_PRESENT_MASK;
>
> This needs a comment:
>
>         /*
>          * There are two cases in which execonly is false: 1) for
>          * non-EPT page tables, in which case we need to set the
>          * P bit; 2) for EPT page tables where an X-- page table

In the scenario of non-EPT shadow page table and non-nested, the
present bit can't be set any more since
context->guest_rsvd_check.bad_mt_xwr is always 0.

Regards,
Wanpeng Li

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

csiph-web