On 25.07.2025 17:06, Edwin Török wrote:
> 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.to...@cloud.com>
> ---
> 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);
I'm fine with this change, and in isolation it can have my ack.
> --- 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 */
I'm not happy about this change: PAGE_SIZE is a Xen-internal entity, which
has no specific meaning in the public interface. (The fact that under io/
there are a number of similar references doesn't justify the use here.)
Jan
