Re: [PATCH 1/3] x86: tolerate running on EFI runtime services page tables in map_domain_page()

[Andrew Cooper <andrew.cooper3@citrix.com>]

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On 23/10/14 14:44, Jan Beulich wrote:
> In the event of a #PF while inan EFI runtime service function we

"in an"

> otherwise can't dump the page tables, making the analysis of the
> problem more cumbersome.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/domain_page.c
> +++ b/xen/arch/x86/domain_page.c
> @@ -7,6 +7,7 @@
>   */
>  
>  #include <xen/domain_page.h>
> +#include <xen/efi.h>
>  #include <xen/mm.h>
>  #include <xen/perfc.h>
>  #include <xen/pfn.h>
> @@ -37,11 +38,14 @@ static inline struct vcpu *mapcache_curr
>       */
>      if ( unlikely(pagetable_is_null(v->arch.guest_table)) && is_pv_vcpu(v) )
>      {
> +        unsigned long cr3;
> +

This will need an __maybe_unused to compile in a non-debug build.

>          /* If we really are idling, perform lazy context switch now. */
>          if ( (v = idle_vcpu[smp_processor_id()]) == current )
>              sync_local_execstate();
>          /* We must now be running on the idle page table. */
> -        ASSERT(read_cr3() == __pa(idle_pg_table));
> +        ASSERT((cr3 = read_cr3()) == __pa(idle_pg_table) ||
> +               (efi_enabled && cr3 == efi_rs_page_table()));
>      }
>  
>      return v;
> --- a/xen/arch/x86/efi/stub.c
> +++ b/xen/arch/x86/efi/stub.c
> @@ -9,6 +9,12 @@ const bool_t efi_enabled = 0;
>  
>  void __init efi_init_memory(void) { }
>  
> +paddr_t efi_rs_page_table(void)
> +{
> +    BUG();
> +    return 0;

Is the return strictly needed?  The __builtin_unreachable() in BUG()
should prevent the compiler from complaining.

~Andrew

> +}
> +
>  unsigned long efi_get_time(void)
>  {
>      BUG();
> --- a/xen/common/efi/runtime.c
> +++ b/xen/common/efi/runtime.c
> @@ -98,6 +98,11 @@ void efi_rs_leave(unsigned long cr3)
>      stts();
>  }
>  
> +paddr_t efi_rs_page_table(void)
> +{
> +    return virt_to_maddr(efi_l4_pgtable);
> +}
> +
>  unsigned long efi_get_time(void)
>  {
>      EFI_TIME time;
> --- a/xen/include/xen/efi.h
> +++ b/xen/include/xen/efi.h
> @@ -28,6 +28,7 @@ struct xenpf_efi_runtime_call;
>  struct compat_pf_efi_runtime_call;
>  
>  void efi_init_memory(void);
> +paddr_t efi_rs_page_table(void);
>  unsigned long efi_get_time(void);
>  void efi_halt_system(void);
>  void efi_reset_system(bool_t warm);
>
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel


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