Re: [XEN PATCH v2 02/15] x86/monitor: guard altp2m usage

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 15 May 2024, Sergiy Kibrik wrote:
> Explicitly check whether altp2m is on for domain when getting altp2m index.
> If explicit call to altp2m_active() always returns false, DCE will remove
> call to altp2m_vcpu_idx().
> 
> The puspose of that is later to be able to disable altp2m support and
> exclude its code from the build completely, when not supported by target
> platform (as of now it's supported for VT-d only).
> 
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> changes in v2:
>  - patch description changed, removed VMX mentioning
>  - guard by altp2m_active() instead of hvm_altp2m_supported()
> ---
>  xen/arch/x86/hvm/monitor.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
> index 2a8ff07ec9..74621000b2 100644
> --- a/xen/arch/x86/hvm/monitor.c
> +++ b/xen/arch/x86/hvm/monitor.c
> @@ -262,6 +262,8 @@ bool hvm_monitor_check_p2m(unsigned long gla, gfn_t gfn, 
> uint32_t pfec,
>      struct vcpu *curr = current;
>      vm_event_request_t req = {};
>      paddr_t gpa = (gfn_to_gaddr(gfn) | (gla & ~PAGE_MASK));
> +    unsigned int altp2m_idx = altp2m_active(curr->domain) ?
> +                              altp2m_vcpu_idx(curr) : 0;
>      int rc;
>  
>      ASSERT(curr->arch.vm_event->send_event);
> @@ -270,7 +272,7 @@ bool hvm_monitor_check_p2m(unsigned long gla, gfn_t gfn, 
> uint32_t pfec,
>       * p2m_get_mem_access() can fail from a invalid MFN and return -ESRCH
>       * in which case access must be restricted.
>       */
> -    rc = p2m_get_mem_access(curr->domain, gfn, &access, 
> altp2m_vcpu_idx(curr));
> +    rc = p2m_get_mem_access(curr->domain, gfn, &access, altp2m_idx);
>  
>      if ( rc == -ESRCH )
>          access = XENMEM_access_n;
> -- 
> 2.25.1
>