Re: [Xen-devel] [PATCH v5 06/15] VMX/altp2m: add code to support EPTP switching and #VE.

["Sahita, Ravi" <ravi.sahita@xxxxxxxxx>]

>From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>Sent: Tuesday, July 14, 2015 6:57 AM
>
>>>> On 14.07.15 at 02:14, <edmund.h.white@xxxxxxxxx> wrote:
>> Implement and hook up the code to enable VMX support of VMFUNC and
>#VE.
>>
>> VMFUNC leaf 0 (EPTP switching) emulation is added in a later patch.
>>
>> Signed-off-by: Ed White <edmund.h.white@xxxxxxxxx>
>>
>> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Acked-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
>> ---
>>  xen/arch/x86/hvm/vmx/vmx.c | 138
>> +++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 138 insertions(+)
>>
>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
>> index 07527dd..38dba6b 100644
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -56,6 +56,7 @@
>>  #include <asm/debugger.h>
>>  #include <asm/apic.h>
>>  #include <asm/hvm/nestedhvm.h>
>> +#include <asm/hvm/altp2m.h>
>>  #include <asm/event.h>
>>  #include <asm/monitor.h>
>>  #include <public/arch-x86/cpuid.h>
>> @@ -1763,6 +1764,104 @@ static void
>> vmx_enable_msr_exit_interception(struct
>> domain *d)
>>                                           MSR_TYPE_W);  }
>>
>> +static void vmx_vcpu_update_eptp(struct vcpu *v) {
>> +    struct domain *d = v->domain;
>> +    struct p2m_domain *p2m = NULL;
>> +    struct ept_data *ept;
>> +
>> +    if ( altp2m_active(d) )
>> +        p2m = p2m_get_altp2m(v);
>> +    if ( !p2m )
>> +        p2m = p2m_get_hostp2m(d);
>> +
>> +    ept = &p2m->ept;
>> +    ept->asr = pagetable_get_pfn(p2m_get_pagetable(p2m));
>> +
>> +    vmx_vmcs_enter(v);
>> +
>> +    __vmwrite(EPT_POINTER, ept_get_eptp(ept));
>> +
>> +    if ( v->arch.hvm_vmx.secondary_exec_control &
>> +        SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS )
>> +        __vmwrite(EPTP_INDEX, vcpu_altp2m(v).p2midx);
>> +
>> +    vmx_vmcs_exit(v);
>> +}
>> +
>> +static void vmx_vcpu_update_vmfunc_ve(struct vcpu *v) {
>> +    struct domain *d = v->domain;
>> +    u32 mask = SECONDARY_EXEC_ENABLE_VM_FUNCTIONS;
>> +
>> +    if ( !cpu_has_vmx_vmfunc )
>> +        return;
>> +
>> +    if ( cpu_has_vmx_virt_exceptions )
>> +        mask |= SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS;
>> +
>> +    vmx_vmcs_enter(v);
>> +
>> +    if ( !d->is_dying && altp2m_active(d) )
>> +    {
>> +        v->arch.hvm_vmx.secondary_exec_control |= mask;
>> +        __vmwrite(VM_FUNCTION_CONTROL,
>VMX_VMFUNC_EPTP_SWITCHING);
>> +        __vmwrite(EPTP_LIST_ADDR,
>> + virt_to_maddr(d->arch.altp2m_eptp));
>> +
>> +        if ( cpu_has_vmx_virt_exceptions )
>> +        {
>> +            p2m_type_t t;
>> +            mfn_t mfn;
>> +
>> +            mfn = get_gfn_query_unlocked(d,
>> + gfn_x(vcpu_altp2m(v).veinfo_gfn), &t);
>> +
>> +            if ( mfn_x(mfn) != INVALID_MFN )
>> +                __vmwrite(VIRT_EXCEPTION_INFO, mfn_x(mfn) << PAGE_SHIFT);
>> +            else
>> +                mask &= ~SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS;
>
>Considering the rest of the function, this is dead code.
>

Right, should be v->arch.hvm_vmx.secondary_exec_control &=...


>> +        }
>> +    }
>> +    else
>> +        v->arch.hvm_vmx.secondary_exec_control &= ~mask;
>> +
>> +    __vmwrite(SECONDARY_VM_EXEC_CONTROL,
>> +        v->arch.hvm_vmx.secondary_exec_control);
>> +
>> +    vmx_vmcs_exit(v);
>> +}
>> +
>> +static bool_t vmx_vcpu_emulate_ve(struct vcpu *v) {
>> +    bool_t rc = 0;
>> +    ve_info_t *veinfo = gfn_x(vcpu_altp2m(v).veinfo_gfn) != INVALID_GFN
>?
>> +        hvm_map_guest_frame_rw(gfn_x(vcpu_altp2m(v).veinfo_gfn), 0) :
>> +NULL;
>> +
>> +    if ( !veinfo )
>> +        return 0;
>> +
>> +    if ( veinfo->semaphore != 0 )
>> +        goto out;
>> +
>> +    rc = 1;
>> +
>> +    veinfo->exit_reason = EXIT_REASON_EPT_VIOLATION;
>> +    veinfo->semaphore = ~0l;
>
>Isn't semaphore a 32-bit quantity?
>

Yes.

>> +    veinfo->eptp_index = vcpu_altp2m(v).p2midx;
>> +
>> +    vmx_vmcs_enter(v);
>> +    __vmread(EXIT_QUALIFICATION, &veinfo->exit_qualification);
>> +    __vmread(GUEST_LINEAR_ADDRESS, &veinfo->gla);
>> +    __vmread(GUEST_PHYSICAL_ADDRESS, &veinfo->gpa);
>> +    vmx_vmcs_exit(v);
>> +
>> +    hvm_inject_hw_exception(TRAP_virtualisation,
>> +                            HVM_DELIVER_NO_ERROR_CODE);
>> +
>> +out:
>
>Un-indented label again.
>

Got it.

>> @@ -2744,6 +2846,42 @@ void vmx_vmexit_handler(struct cpu_user_regs
>*regs)
>>      /* Now enable interrupts so it's safe to take locks. */
>>      local_irq_enable();
>>
>> +    /*
>> +     * If the guest has the ability to switch EPTP without an exit,
>> +     * figure out whether it has done so and update the altp2m data.
>> +     */
>> +    if ( altp2m_active(v->domain) &&
>> +        (v->arch.hvm_vmx.secondary_exec_control &
>> +        SECONDARY_EXEC_ENABLE_VM_FUNCTIONS) )
>
>Indentation.
>

Yep.

>> +    {
>> +        unsigned long idx;
>> +
>> +        if ( v->arch.hvm_vmx.secondary_exec_control &
>> +            SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS )
>> +            __vmread(EPTP_INDEX, &idx);
>> +        else
>> +        {
>> +            unsigned long eptp;
>> +
>> +            __vmread(EPT_POINTER, &eptp);
>> +
>> +            if ( (idx = p2m_find_altp2m_by_eptp(v->domain, eptp)) ==
>> +                 INVALID_ALTP2M )
>> +            {
>> +                gdprintk(XENLOG_ERR, "EPTP not found in alternate p2m 
>> list\n");
>> +                domain_crash(v->domain);
>> +            }
>> +        }
>> +
>> +        if ( (uint16_t)idx != vcpu_altp2m(v).p2midx )
>
>Is this cast really necessary?
>

Yes - The index is 16-bits, this reflects how the field is specified in the 
vmcs also.

>> +        {
>> +            BUG_ON(idx >= MAX_ALTP2M);
>> +            atomic_dec(&p2m_get_altp2m(v)->active_vcpus);
>> +            vcpu_altp2m(v).p2midx = (uint16_t)idx;
>
>This one surely isn't (or else the field type is wrong).
>

Again required. idx can't be uint16_t because __vmread() requires unsigned 
long*, but the index is 16 bits.

Thanks,
Ravi

>Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel