[RFC PATCH v1 01/10] pmu.h: add a BUILD_BUG_ON to ensure it fits within one page

[Edwin Török <edwin.torok@xxxxxxxxx>]

Linux already has a similar BUILD_BUG_ON.
Currently this struct is ~224 bytes on x86-64.

No functional change.

Signed-off-by: Edwin Török <edwin.torok@xxxxxxxxx>
---
 xen/arch/x86/cpu/vpmu.c  | 1 +
 xen/include/public/pmu.h | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/xen/arch/x86/cpu/vpmu.c b/xen/arch/x86/cpu/vpmu.c
index c28192ea26..7be79c2d00 100644
--- a/xen/arch/x86/cpu/vpmu.c
+++ b/xen/arch/x86/cpu/vpmu.c
@@ -401,6 +401,7 @@ static int vpmu_arch_initialise(struct vcpu *v)
     uint8_t vendor = current_cpu_data.x86_vendor;
     int ret;
 
+    BUILD_BUG_ON(sizeof(struct xen_pmu_data) > PAGE_SIZE);
     BUILD_BUG_ON(sizeof(struct xen_pmu_intel_ctxt) > XENPMU_CTXT_PAD_SZ);
     BUILD_BUG_ON(sizeof(struct xen_pmu_amd_ctxt) > XENPMU_CTXT_PAD_SZ);
     BUILD_BUG_ON(sizeof(struct xen_pmu_regs) > XENPMU_REGS_PAD_SZ);
diff --git a/xen/include/public/pmu.h b/xen/include/public/pmu.h
index af8b7babdd..15decc024d 100644
--- a/xen/include/public/pmu.h
+++ b/xen/include/public/pmu.h
@@ -93,6 +93,9 @@ DEFINE_XEN_GUEST_HANDLE(xen_pmu_params_t);
  * Architecture-independent fields of xen_pmu_data are WO for the hypervisor
  * and RO for the guest but some fields in xen_pmu_arch can be writable
  * by both the hypervisor and the guest (see arch-$arch/pmu.h).
+ *
+ * PAGE_SIZE bytes of memory are allocated.
+ * This struct cannot be larger than PAGE_SIZE.
  */
 struct xen_pmu_data {
     /* Interrupted VCPU */
-- 
2.47.1