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x86/hyperv: Restrict get_vtl to only VTL platforms

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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: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/1695182675-13405-1-git-send-email-ssengar@linux.microsoft.com
This commit is contained in:
Saurabh Sengar 2023-09-19 21:04:35 -07:00 committed by Wei Liu
parent ce9ecca023
commit f2a55d08d7
1 changed files with 7 additions and 4 deletions
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11
arch/x86/hyperv/hv_init.c
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@ -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 @@ skip_hypercall_pg_init:
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;