Re: [Xen-devel] [PATCH RFC 10/12] x86/np2m: implement sharing of np2m between vCPUs

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 07/18/2017 11:34 AM, Sergey Dyasli wrote:
> Modify p2m_get_nestedp2m() to allow sharing a np2m between multiple
> vcpus with the same np2m_base (L1 EPTP value in VMCS12).
> 
> np2m_schedule_in/out() callbacks are added to context_switch() as well
> as pseudo schedule-out is performed during virtual_vmexit().
> 
> Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
> ---
>  xen/arch/x86/domain.c       |  2 ++
>  xen/arch/x86/hvm/vmx/vvmx.c |  4 ++++
>  xen/arch/x86/mm/p2m.c       | 29 +++++++++++++++++++++++++++--
>  3 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index dd8bf1302f..38c86a5ded 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1642,6 +1642,7 @@ void context_switch(struct vcpu *prev, struct vcpu 
> *next)
>      {
>          _update_runstate_area(prev);
>          vpmu_switch_from(prev);
> +        np2m_schedule_out();
>      }
>  
>      if ( is_hvm_domain(prevd) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> @@ -1690,6 +1691,7 @@ void context_switch(struct vcpu *prev, struct vcpu 
> *next)
>  
>          /* Must be done with interrupts enabled */
>          vpmu_switch_to(next);
> +        np2m_schedule_in();
>      }
>  
>      /* Ensure that the vcpu has an up-to-date time base. */
> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
> index 7b193767cd..2203d541ea 100644
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -1187,6 +1187,7 @@ static void virtual_vmentry(struct cpu_user_regs *regs)
>  
>      /* Setup virtual ETP for L2 guest*/
>      if ( nestedhvm_paging_mode_hap(v) )
> +        /* This will setup the initial np2m for the nested vCPU */
>          __vmwrite(EPT_POINTER, get_shadow_eptp(v));
>      else
>          __vmwrite(EPT_POINTER, get_host_eptp(v));
> @@ -1353,6 +1354,9 @@ static void virtual_vmexit(struct cpu_user_regs *regs)
>           !(v->arch.hvm_vcpu.guest_efer & EFER_LMA) )
>          shadow_to_vvmcs_bulk(v, ARRAY_SIZE(gpdpte_fields), gpdpte_fields);
>  
> +    /* This will clear current pCPU bit in p2m->dirty_cpumask */
> +    np2m_schedule_out();
> +
>      vmx_vmcs_switch(v->arch.hvm_vmx.vmcs_pa, nvcpu->nv_n1vmcx_pa);
>  
>      nestedhvm_vcpu_exit_guestmode(v);
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 364fdd8c13..480459ae51 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1830,6 +1830,7 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
>      struct domain *d = v->domain;
>      struct p2m_domain *p2m;
>      uint64_t np2m_base = nhvm_vcpu_p2m_base(v);
> +    unsigned int i;
>  
>      /* Mask out low bits; this avoids collisions with P2M_BASE_EADDR */
>      np2m_base &= ~(0xfffull);
> @@ -1843,10 +1844,34 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
>      if ( p2m ) 
>      {
>          p2m_lock(p2m);
> -        if ( p2m->np2m_base == np2m_base || p2m->np2m_base == P2M_BASE_EADDR 
> )
> +        if ( p2m->np2m_base == np2m_base )
>          {
> -            if ( p2m->np2m_base == P2M_BASE_EADDR )
> +            /* Check if np2m was flushed just before the lock */
> +            if ( nv->np2m_generation != p2m->np2m_generation )
>                  nvcpu_flush(v);
> +            /* np2m is up-to-date */
> +            p2m->np2m_base = np2m_base;
> +            assign_np2m(v, p2m);
> +            nestedp2m_unlock(d);

This function now has three copies of the above four lines.  What about
folding in something like the attached?

 -George

Attachment: code-sharing.diff
Description: Text Data

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