Commit f2a55d08 authored by Saurabh Sengar's avatar Saurabh Sengar Committed by Wei Liu
Browse files

x86/hyperv: Restrict get_vtl to only VTL platforms 



When Linux runs in a non-default VTL (CONFIG_HYPERV_VTL_MODE=y),
get_vtl() must never fail as its return value 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: default avatarSaurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/1695182675-13405-1-git-send-email-ssengar@linux.microsoft.com
parent ce9ecca0

arch/x86/hyperv/hv_init.c

+7 −4
Original line number Diff line number Diff line
@@ -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
@@ -604,7 +608,6 @@ 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();



	return;