Re: [PATCH v3] x86/hyper-v: Mark TLFS structures packed

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

>  /* Define virtual processor assist page structure. */
>  struct hv_vp_assist_page {
> @@ -519,7 +519,7 @@ struct hv_vp_assist_page {
>  	__u64 nested_enlightenments_control[2];
>  	__u32 enlighten_vmentry;
>  	__u64 current_nested_vmcs;
> -};
> +} __packed;
>  

This particular structure wasn't properly padded: u32 padding is missing
between 'enlighten_vmentry' and 'current_nested_vmcs'.

>  struct hv_enlightened_vmcs {
>  	u32 revision_id;
> @@ -693,7 +693,7 @@ struct hv_enlightened_vmcs {
>  		u32 nested_flush_hypercall:1;
>  		u32 msr_bitmap:1;
>  		u32 reserved:30;
> -	} hv_enlightenments_control;
> +	}  __packed hv_enlightenments_control;
>  	u32 hv_vp_id;
>  
>  	u64 hv_vm_id;
> @@ -703,7 +703,7 @@ struct hv_enlightened_vmcs {
>  	u64 padding64_5[7];
>  	u64 xss_exit_bitmap;
>  	u64 padding64_6[7];
> -};
> +} __packed;

struct hv_enlightened_vmcs also has a hole: we need an u16 padding after
'u16 host_tr_selector'.

Both these problems led to Enlightened VMCS for Hyper-V on KVM being
completely broken.

As this is not yet merged, v4 is coming to rescue!

-- 
Vitaly