RE: [PATCH-for-5.1 v2 1/1] accel/xen: Fix xen_enabled() behavior on target-agnostic objects

[Paul Durrant]

> -----Original Message-----
> From: Philippe Mathieu-Daudé <philmd@redhat.com>
> Sent: 04 August 2020 08:50
> To: qemu-devel@nongnu.org
> Cc: Peter Maydell <peter.maydell@linaro.org>; Anthony Perard 
> <anthony.perard@citrix.com>; Paolo
> Bonzini <pbonzini@redhat.com>; Stefano Stabellini <sstabellini@kernel.org>; 
> xen-
> devel@lists.xenproject.org; Paul Durrant <paul@xen.org>; Philippe 
> Mathieu-Daudé <philmd@redhat.com>;
> Paul Durrant <pdurrant@amazon.com>
> Subject: [PATCH-for-5.1 v2 1/1] accel/xen: Fix xen_enabled() behavior on 
> target-agnostic objects
> 
> CONFIG_XEN is generated by configure and stored in "config-target.h",
> which is (obviously) only include for target-specific objects.
> This is a problem for target-agnostic objects as CONFIG_XEN is never
> defined and xen_enabled() is always inlined as 'false'.
> 
> Fix by following the KVM schema, defining CONFIG_XEN_IS_POSSIBLE
> when we don't know to force the call of the non-inlined function,
> returning the xen_allowed boolean.
> 
> Fixes: da278d58a092 ("accel: Move Xen accelerator code under accel/xen/")
> Reported-by: Paul Durrant <pdurrant@amazon.com>
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/sysemu/xen.h   | 18 ++++++++++++++----
>  accel/stubs/xen-stub.c |  2 ++
>  accel/xen/xen-all.c    |  7 +------
>  3 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/include/sysemu/xen.h b/include/sysemu/xen.h
> index 1ca292715e..2c2c429ea8 100644
> --- a/include/sysemu/xen.h
> +++ b/include/sysemu/xen.h
> @@ -8,9 +8,19 @@
>  #ifndef SYSEMU_XEN_H
>  #define SYSEMU_XEN_H
> 
> -#ifdef CONFIG_XEN
> +#ifdef NEED_CPU_H
> +# ifdef CONFIG_XEN
> +#  define CONFIG_XEN_IS_POSSIBLE
> +# endif
> +#else
> +# define CONFIG_XEN_IS_POSSIBLE
> +#endif
> 
> -bool xen_enabled(void);
> +#ifdef CONFIG_XEN_IS_POSSIBLE
> +
> +extern bool xen_allowed;
> +
> +#define xen_enabled()           (xen_allowed)

Can this not move ahead of the #ifdef now (since xen_allowed is present in both 
xen-stub and xen-all)? I think this is what Peter was saying in his option 
'(2)'.

  Paul

> 
>  #ifndef CONFIG_USER_ONLY
>  void xen_hvm_modified_memory(ram_addr_t start, ram_addr_t length);
> @@ -18,7 +28,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
>                     struct MemoryRegion *mr, Error **errp);
>  #endif
> 
> -#else /* !CONFIG_XEN */
> +#else /* !CONFIG_XEN_IS_POSSIBLE */
> 
>  #define xen_enabled() 0
>  #ifndef CONFIG_USER_ONLY
> @@ -33,6 +43,6 @@ static inline void xen_ram_alloc(ram_addr_t ram_addr, 
> ram_addr_t size,
>  }
>  #endif
> 
> -#endif /* CONFIG_XEN */
> +#endif /* CONFIG_XEN_IS_POSSIBLE */
> 
>  #endif
> diff --git a/accel/stubs/xen-stub.c b/accel/stubs/xen-stub.c
> index dcca4e678a..8ae658acff 100644
> --- a/accel/stubs/xen-stub.c
> +++ b/accel/stubs/xen-stub.c
> @@ -9,6 +9,8 @@
>  #include "hw/xen/xen.h"
>  #include "qapi/qapi-commands-misc.h"
> 
> +bool xen_allowed;
> +
>  void xenstore_store_pv_console_info(int i, Chardev *chr)
>  {
>  }
> diff --git a/accel/xen/xen-all.c b/accel/xen/xen-all.c
> index 0c24d4b191..60b971d0a8 100644
> --- a/accel/xen/xen-all.c
> +++ b/accel/xen/xen-all.c
> @@ -32,12 +32,7 @@
>      do { } while (0)
>  #endif
> 
> -static bool xen_allowed;
> -
> -bool xen_enabled(void)
> -{
> -    return xen_allowed;
> -}
> +bool xen_allowed;
> 
>  xc_interface *xen_xc;
>  xenforeignmemory_handle *xen_fmem;
> --
> 2.21.3