Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> writes:
> For non VTL platforms vtl is always 0, and there is no need of
> get_vtl function. For VTL platforms get_vtl should always succeed
> and should return the correct VTL.
Nitpicking, an alternative summary:
"""
When Linux runs in a non-default VTL (CONFIG_HYPERV_VTL_MODE=y),
get_vtl() must never fail as the result it returns is used in
negotiations with the host. In the more generic case,
(CONFIG_HYPERV_VTL_MODE=n) the VTL is always zero so there's no need to
do the hypercall.
Make get_vtl() BUG() in case of failure and put the implementation under
"if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)" to avoid the call altogether in
the most generic use case.
"""
>
> Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> [V2]
> - Put the if else at function definition rather then at the caller
>
> arch/x86/hyperv/hv_init.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 783ed339f341..f0128fd4031d 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -394,6 +394,7 @@ static void __init hv_get_partition_id(void)
> local_irq_restore(flags);
> }
>
> +#if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
> static u8 __init get_vtl(void)
> {
> u64 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_REGISTERS;
> @@ -416,13 +417,16 @@ static u8 __init get_vtl(void)
> if (hv_result_success(ret)) {
> ret = output->as64.low & HV_X64_VTL_MASK;
> } else {
> - pr_err("Failed to get VTL(%lld) and set VTL to zero by default.\n", ret);
> - ret = 0;
> + pr_err("Failed to get VTL(error: %lld) exiting...\n", ret);
> + BUG();
> }
>
> local_irq_restore(flags);
> return ret;
> }
> +#else
> +static inline u8 get_vtl(void) { return 0; }
> +#endif
>
> /*
> * This function is to be invoked early in the boot sequence after the
> @@ -604,8 +608,7 @@ void __init hyperv_init(void)
> hv_query_ext_cap(0);
>
> /* Find the VTL */
> - if (!ms_hyperv.paravisor_present && hv_isolation_type_snp())
> - ms_hyperv.vtl = get_vtl();
> + ms_hyperv.vtl = get_vtl();
>
> return;
--
Vitaly
