Misc HW patches for 2026-03-23

[PULL 15/27] hw/hyperv: Fix SynIC not initialized except on first vCPU

Philippe Mathieu-Daudé posted 27 patches 1 week, 3 days ago

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[PULL 15/27] hw/hyperv: Fix SynIC not initialized except on first vCPU

Posted by Philippe Mathieu-Daudé 1 week, 3 days ago

From: Sourav Poddar <souravpoddar93042@gmail.com>

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(), 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.

Fixes: c4cf32fc63f1 ("kvm/hyperv: add synic feature to CPU only if its not enabled")
Reported-by: Xudong Hao <xudong.hao@intel.com>
Co-authored-by: Ani Sinha <anisinha@redhat.com>
Signed-off-by: Sourav Poddar <souravpoddar93042@gmail.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Message-ID: <20260320154752.204725-1-anisinha@redhat.com>
[PMD: Reworded subject]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/hyperv/hyperv.h | 1 +
 hw/hyperv/hyperv.c         | 5 +++++
 target/i386/kvm/hyperv.c   | 2 +-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/hw/hyperv/hyperv.h b/include/hw/hyperv/hyperv.h
index 63a8b65278f..23091301d06 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/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
index aa278b179e6..a42c2850e35 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);
+}
+
 static void synic_update(SynICState *synic, bool sctl_enable,
                          hwaddr msg_page_addr, hwaddr event_page_addr)
 {
diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
index bd3c26d02b5..420c76b5ff5 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