> On 21 Mar 2026, at 11:50 AM, Sourav Poddar <[email protected]>
> wrote:
>
> hyperv_is_synic_enabled() is a global flag that returns true after the
> first CPU initializes SynIC. With -smp N, all subsequent CPUs skip
> hyperv_x86_synic_add() in hyperv_enable_synic(), leaving them without
> a synic object. This causes get_synic() to return NULL, making
> hyperv_sint_route_new() fail and triggering an assertion crash in
> hyperv_testdev.
>
> Fix by introducing hyperv_is_synic_present() which checks per-CPU
> whether a synic object is already attached instead of using the global
> flag.
I have sent this here
https://lists.nongnu.org/archive/html/qemu-devel/2026-03/msg06300.html
>
> Fixes: c4cf32fc63f1 ("kvm/hyperv: add synic feature to CPU only if its not
> enabled")
> Reported-by: Xudong Hao
> Signed-off-by: Sourav Poddar <[email protected]>
> ---
> hw/hyperv/hyperv.c | 5 +++++
> include/hw/hyperv/hyperv.h | 1 +
> target/i386/kvm/hyperv.c | 2 +-
> 3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> index 27e323a819..ff53cbc699 100644
> --- a/hw/hyperv/hyperv.c
> +++ b/hw/hyperv/hyperv.c
> @@ -60,6 +60,11 @@ static SynICState *get_synic(CPUState *cs)
> return SYNIC(object_resolve_path_component(OBJECT(cs), "synic"));
> }
>
> +bool hyperv_is_synic_present(CPUState *cs)
> +{
> + return get_synic(cs) != NULL;
> +}
> +
> static void synic_update(SynICState *synic, bool sctl_enable,
> hwaddr msg_page_addr, hwaddr event_page_addr)
> {
> diff --git a/include/hw/hyperv/hyperv.h b/include/hw/hyperv/hyperv.h
> index 63a8b65278..23091301d0 100644
> --- a/include/hw/hyperv/hyperv.h
> +++ b/include/hw/hyperv/hyperv.h
> @@ -81,6 +81,7 @@ void hyperv_synic_reset(CPUState *cs);
> void hyperv_synic_update(CPUState *cs, bool enable,
> hwaddr msg_page_addr, hwaddr event_page_addr);
> bool hyperv_is_synic_enabled(void);
> +bool hyperv_is_synic_present(CPUState *cs);
>
> /*
> * Process HVCALL_RESET_DEBUG_SESSION hypercall.
> diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
> index bd3c26d02b..420c76b5ff 100644
> --- a/target/i386/kvm/hyperv.c
> +++ b/target/i386/kvm/hyperv.c
> @@ -27,7 +27,7 @@ int hyperv_x86_synic_add(X86CPU *cpu)
> int hyperv_enable_synic(X86CPU *cpu)
> {
> int ret = 0;
> - if (!hyperv_is_synic_enabled()) {
> + if (!hyperv_is_synic_present(CPU(cpu))) {
> ret = hyperv_x86_synic_add(cpu);
> }
> return ret;
> --
> 2.53.0
>
