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Groups > linux.kernel > #1442242
| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 4/5] mmu: change unconditional setting of the u bit in fault bitmap |
| Date | 2016-07-13 11:10 +0200 |
| Message-ID | <rUol3-VT-13@gated-at.bofh.it> (permalink) |
| References | <rUec2-2Bd-9@gated-at.bofh.it> <rUelH-2F3-7@gated-at.bofh.it> <rUnIl-rS-19@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 13/07/2016 10:23, Paolo Bonzini wrote:
>
>
> On 13/07/2016 00:18, Bandan Das wrote:
>> For the nested EPT case, we assume that the read bit (u) is
>> always set since we used to unconditionally set it in set_spte().
>> Modify it to only be set when host ept execute only support
>> isn't present.
>>
>> Signed-off-by: Bandan Das <bsd@redhat.com>
>> ---
>> arch/x86/kvm/mmu.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index c364dcb..566eea5 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -3923,9 +3923,10 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu,
>> * clearer.
>> */
>> smap = cr4_smap && u && !uf && !ff;
>> - } else
>> - /* Not really needed: no U/S accesses on ept */
>> - u = 1;
>> + } else {
>> + if (shadow_present_mask)
>> + u = 1;
... in fact I think this should be removed completely.
If shadow_present_mask is set, the R bit will always be set in a present
PTE and FNAME(gpte_access) will change that to ACC_USER_MASK---which in
turn means that u=1.
Paolo
>> + }
>>
>> fault = (ff && !x) || (uf && !u) || (wf && !w) ||
>> (smapf && smap);
>>
>
> This is needed too, in order to look up with the correct uf:
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 003618e324ce..941d345ebd2c 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6014,12 +6014,14 @@ static int handle_ept_violation(struct kvm_vcpu
> *vcpu)
> gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
> trace_kvm_page_fault(gpa, exit_qualification);
>
> - /* It is a write fault? */
> + /* it is a read fault? */
> + error_code = (exit_qualification << 2) & PFERR_USER_MASK;
> + /* it is a write fault? */
> error_code = exit_qualification & PFERR_WRITE_MASK;
> /* It is a fetch fault? */
> error_code |= (exit_qualification << 2) & PFERR_FETCH_MASK;
> /* ept page table is present? */
> - error_code |= (exit_qualification >> 3) & PFERR_PRESENT_MASK;
> + error_code |= (exit_qualification & 0x38) != 0;
>
> vcpu->arch.exit_qualification = exit_qualification;
>
>
> Otherwise you always lookup the permission bitmap for an uf=0 case.
> This was the meaning of the "Not really needed" comment.
>
> Paolo
>
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[PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das <bsd@redhat.com> - 2016-07-13 00:20 +0200
[PATCH v2 2/5] mmu: don't set the present bit unconditionally Bandan Das <bsd@redhat.com> - 2016-07-13 00:30 +0200
Re: [PATCH v2 2/5] mmu: don't set the present bit unconditionally Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 10:20 +0200
[PATCH v2 4/5] mmu: change unconditional setting of the u bit in fault bitmap Bandan Das <bsd@redhat.com> - 2016-07-13 00:30 +0200
Re: [PATCH v2 4/5] mmu: change unconditional setting of the u bit in fault bitmap Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 10:30 +0200
Re: [PATCH v2 4/5] mmu: change unconditional setting of the u bit in fault bitmap Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 11:10 +0200
[PATCH v2 3/5] mmu: remove is_present_gpte() Bandan Das <bsd@redhat.com> - 2016-07-13 00:30 +0200
[PATCH v2 5/5] vmx: advertise support for ept execute only Bandan Das <bsd@redhat.com> - 2016-07-13 00:30 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 11:30 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Fam Zheng <famz@redhat.com> - 2016-07-13 12:00 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 12:10 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das <bsd@redhat.com> - 2016-07-13 17:10 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini <pbonzini@redhat.com> - 2016-07-13 17:30 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das <bsd@redhat.com> - 2016-07-13 17:50 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini <pbonzini@redhat.com> - 2016-07-14 09:00 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das <bsd@redhat.com> - 2016-07-14 19:40 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Paolo Bonzini <pbonzini@redhat.com> - 2016-07-14 20:30 +0200
Re: [PATCH v2 0/5] Add support for EPT execute only for nested hypervisors Bandan Das <bsd@redhat.com> - 2016-07-14 21:00 +0200
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