Re: [RFC PATCH v2 13/22] i386/xen: implement HYPERVISOR_memory_op

[Paul Durrant]

On 09/12/2022 09:56, David Woodhouse wrote:
> From: Joao Martins <joao.m.martins@oracle.com>
>
> Specifically XENMEM_add_to_physmap with space XENMAPSPACE_shared_info to
> allow the guest to set its shared_info page.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> [dwmw2: Use the xen_overlay device]
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   target/i386/trace-events |  1 +
>   target/i386/xen.c        | 59 +++++++++++++++++++++++++++++++++++++++-
>   2 files changed, 59 insertions(+), 1 deletion(-)
[snip]
> +static bool kvm_xen_hcall_memory_op(struct kvm_xen_exit *exit,
> +                                   int cmd, uint64_t arg, X86CPU *cpu)
> +{
> +    CPUState *cs = CPU(cpu);
> +    int err = 0;
> +
> +    switch (cmd) {
> +    case XENMEM_add_to_physmap: {
> +            struct xen_add_to_physmap xatp;
> +
> +            err = kvm_copy_from_gva(cs, arg, &xatp, sizeof(xatp));
> +            if (err) {
> +                break;
> +            }
> +
> +            switch (xatp.space) {
> +            case XENMAPSPACE_shared_info:
> +                break;
> +            default:
> +                err = -ENOSYS;
> +                break;

Don't you want to return false here?

  Paul

> +            }
> +
> +            err = xen_set_shared_info(cs, xatp.gpfn);
> +            break;
> +         }
> +
> +    default:
> +            return false;
> +    }
> +
> +    exit->u.hcall.result = err;
> +    return true;
> +}
> +