Re: [RFC PATCH v2 15/22] i386/xen: implement HYPERVISOR_vcpu_op

[Paul Durrant]

On 09/12/2022 09:56, David Woodhouse wrote:
> From: Joao Martins <joao.m.martins@oracle.com>
>
> This is simply when guest tries to register a vcpu_info
> and since vcpu_info placement is optional in the minimum ABI
> therefore we can just fail with -ENOSYS
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   target/i386/xen.c | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
>
> diff --git a/target/i386/xen.c b/target/i386/xen.c
> index 2847b4f864..9d1daadee1 100644
> --- a/target/i386/xen.c
> +++ b/target/i386/xen.c
> @@ -19,6 +19,7 @@
>   #include "standard-headers/xen/version.h"
>   #include "standard-headers/xen/memory.h"
>   #include "standard-headers/xen/hvm/hvm_op.h"
> +#include "standard-headers/xen/vcpu.h"
>   
>   static int kvm_gva_rw(CPUState *cs, uint64_t gva, void *_buf, size_t sz,
>                         bool is_write)
> @@ -194,6 +195,25 @@ static bool kvm_xen_hcall_hvm_op(struct kvm_xen_exit *exit,
>       }
>   }
>   
> +static bool kvm_xen_hcall_vcpu_op(struct kvm_xen_exit *exit, X86CPU *cpu,
> +                                  int cmd, int vcpu_id, uint64_t arg)
> +{
> +    int err;
> +
> +    switch (cmd) {
> +    case VCPUOP_register_vcpu_info:
> +        /* no vcpu info placement for now */
> +        err = -ENOSYS;

Again, should this patch be deferred until we actually implement 
something useful here? I.e. folding it into the subsequent patch? It's 
not like the boilerplate is massive.

  Paul