diff mbox series

[XEN,v8,07/22] xen/arm: ffa: enforce dependency on 4k pages

Message ID 20230413071424.3273490-8-jens.wiklander@linaro.org (mailing list archive)
State New, archived
Headers show
Series Xen FF-A mediator | expand

Commit Message

Jens Wiklander April 13, 2023, 7:14 a.m. UTC 
Adds a BUILD_BUG_ON() to assert the dependency on 4k pages in the FF-A
mediator since the current implementation only works if Xen page size is
the same as the FFA page size.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
---
 xen/arch/arm/tee/ffa.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

Comments

Henry Wang April 13, 2023, 10:55 a.m. UTC | #1 
Hi Jens,

> -----Original Message-----
> Subject: [XEN PATCH v8 07/22] xen/arm: ffa: enforce dependency on 4k pages
> 
> Adds a BUILD_BUG_ON() to assert the dependency on 4k pages in the FF-A
> mediator since the current implementation only works if Xen page size is
> the same as the FFA page size.
> 
> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

Reviewed-by: Henry Wang <Henry.Wang@arm.com>

Kind regards,
Henry
Jens Wiklander April 13, 2023, 1:53 p.m. UTC | #2 
Hi Henry,

On Thu, Apr 13, 2023 at 12:55 PM Henry Wang <Henry.Wang@arm.com> wrote:
>
> Hi Jens,
>
> > -----Original Message-----
> > Subject: [XEN PATCH v8 07/22] xen/arm: ffa: enforce dependency on 4k pages
> >
> > Adds a BUILD_BUG_ON() to assert the dependency on 4k pages in the FF-A
> > mediator since the current implementation only works if Xen page size is
> > the same as the FFA page size.
> >
> > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> > Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
>
> Reviewed-by: Henry Wang <Henry.Wang@arm.com>

I'll add that.

Thanks,
Jens

>
> Kind regards,
> Henry
diff mbox series

Patch

diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index cf7b7545aa03..90ed71cbfda3 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -57,6 +57,16 @@ 
 #define FFA_MY_VERSION          MAKE_FFA_VERSION(FFA_MY_VERSION_MAJOR, \
                                                  FFA_MY_VERSION_MINOR)
 
+/*
+ * The FF-A specification explicitly works with 4K pages as a measure of
+ * memory size, for example, FFA_RXTX_MAP takes one parameter "RX/TX page
+ * count" which is the number of contiguous 4K pages allocated. Xen may use
+ * a different page size depending on the configuration to avoid confusion
+ * with PAGE_SIZE use a special define when it's a page size as in the FF-A
+ * specification.
+ */
+#define FFA_PAGE_SIZE                   SZ_4K
+
 /*
  * Flags and field values used for the MSG_SEND_DIRECT_REQ/RESP:
  * BIT(31): Framework or partition message
@@ -256,6 +266,17 @@  static bool ffa_probe(void)
     unsigned int major_vers;
     unsigned int minor_vers;
 
+    /*
+     * FF-A often works in units of 4K pages and currently it's assumed
+     * that we can map memory using that granularity. See also the comment
+     * above the FFA_PAGE_SIZE define.
+     *
+     * It is possible to support a PAGE_SIZE larger than 4K in Xen, but
+     * until that is fully handled in this code make sure that we only use
+     * 4K page sizes.
+     */
+    BUILD_BUG_ON(PAGE_SIZE != FFA_PAGE_SIZE);
+
     /*
      * psci_init_smccc() updates this value with what's reported by EL-3
      * or secure world.