From: Wei Hu <[email protected]> Upstream mshv_synic_cpu_init()/_exit() skip programming the SynIC SIMP/SIEFP/SCONTROL registers when VMBus is active (hv_vmbus_exists()), assuming VMBus's hv_hyp_synic_enable_regs() already provisioned them.
That assumption is wrong for a *nested* root partition. There, VMBus programs the *nested* SynIC MSRs (HV_X64_MSR_NESTED_SIMP, ...) via hv_set_msr()'s nested remap, while mshv_synic reads/writes the *non-nested* SynIC MSRs (hv_get/set_non_nested_msr). As a result mshv maps the wrong message page, never receives the SYNIC intercept message that carries the async hypercall completion, and mshv_async_hvcall_handler blocks forever -- hanging SEV-SNP guest creation from user space. Gate the "VMBus owns the SynIC registers" optimization on !hv_nested so that a nested root partition programs its own non-nested SynIC registers, restoring correct intercept/async-hypercall delivery. No change for a non-nested (bare-metal) root. Signed-off-by: Wei Hu <[email protected]> --- drivers/hv/mshv_synic.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c index 7c168e5a740d..7d714ee5d226 100644 --- a/drivers/hv/mshv_synic.c +++ b/drivers/hv/mshv_synic.c @@ -472,7 +472,13 @@ static int mshv_synic_cpu_init(unsigned int cpu) * VMBus owns SIMP/SIEFP/SCONTROL when it is active. * See hv_hyp_synic_enable_regs() for that initialization. */ - bool vmbus_active = hv_vmbus_exists(); + /* + * On a nested root partition VMBus programs the *nested* SynIC MSRs + * (SIMP/SIEFP/SCONTROL) via hv_set_msr()'s nested remap, whereas the + * code below reads/writes the non-nested SynIC MSRs. So when nested, + * do not defer SynIC setup to VMBus -- set up our own registers. + */ + bool vmbus_active = hv_vmbus_exists() && !hv_nested; /* * Map the SYNIC message page. When VMBus is not active the @@ -593,7 +599,13 @@ static int mshv_synic_cpu_exit(unsigned int cpu) struct hv_synic_event_ring_page **event_ring_page = &spages->synic_event_ring_page; /* VMBus owns SIMP/SIEFP/SCONTROL when it is active */ - bool vmbus_active = hv_vmbus_exists(); + /* + * On a nested root partition VMBus programs the *nested* SynIC MSRs + * (SIMP/SIEFP/SCONTROL) via hv_set_msr()'s nested remap, whereas the + * code below reads/writes the non-nested SynIC MSRs. So when nested, + * do not defer SynIC setup to VMBus -- set up our own registers. + */ + bool vmbus_active = hv_vmbus_exists() && !hv_nested; /* Disable the interrupt */ sint.as_uint64 = hv_get_non_nested_msr(HV_MSR_SINT0 + HV_SYNIC_INTERCEPTION_SINT_INDEX); -- 2.43.0
