Re: [PATCH v3 18/34] x86/hyperv: Fix 'struct hv_enlightened_vmcs' definition

Maxim Levitsky
2022-05-11T11:31:22Z

On Thu, 2022-04-14 at 15:19 +0200, Vitaly Kuznetsov wrote:
> Section 1.9 of TLFS v6.0b says:
>
> "All structures are padded in such a way that fields are aligned
> naturally (that is, an 8-byte field is aligned to an offset of 8 bytes
> and so on)".
>
> 'struct enlightened_vmcs' has a glitch:
>
> ...
> struct {
> u32 nested_flush_hypercall:1; /* 836: 0 4 */
> u32 msr_bitmap:1; /* 836: 1 4 */
> u32 reserved:30; /* 836: 2 4 */
> } hv_enlightenments_control; /* 836 4 */
> u32 hv_vp_id; /* 840 4 */
> u64 hv_vm_id; /* 844 8 */
> u64 partition_assist_page; /* 852 8 */
> ...
>
> And the observed values in 'partition_assist_page' make no sense at
> all. Fix the layout by padding the structure properly.
>
> Fixes: 68d1eb72ee99 ("x86/hyper-v: define struct hv_enlightened_vmcs and clean field bits")
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/include/asm/hyperv-tlfs.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 5225a85c08c3..e7ddae8e02c6 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -548,7 +548,7 @@ struct hv_enlightened_vmcs {
> u64 guest_rip;
>
> u32 hv_clean_fields;
> - u32 hv_padding_32;
> + u32 padding32_1;
> u32 hv_synthetic_controls;
> struct {
> u32 nested_flush_hypercall:1;
> @@ -556,7 +556,7 @@ struct hv_enlightened_vmcs {
> u32 reserved:30;
> } __packed hv_enlightenments_control;
> u32 hv_vp_id;
> -
> + u32 padding32_2;
> u64 hv_vm_id;
> u64 partition_assist_page;
> u64 padding64_4[4];

Makes sense.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky