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[PATCH RFC V2 36/37] tcg/mttcg: enable threads to unregister in tcg_ctxs
From: |
Salil Mehta |
Subject: |
[PATCH RFC V2 36/37] tcg/mttcg: enable threads to unregister in tcg_ctxs[] |
Date: |
Tue, 26 Sep 2023 11:36:53 +0100 |
From: Miguel Luis <miguel.luis@oracle.com>
[This patch is just for reference. It has problems as it does not takes care of
the TranslationBlocks and their assigned regions during CPU unrealize]
When using TCG acceleration in a multi-threaded context each vCPU has its own
thread registered in tcg_ctxs[] upon creation and tcg_cur_ctxs stores the
current
number of threads that got created. Although, the lack of a mechanism to
unregister these threads is a problem when exercising vCPU hotplug/unplug
due to the fact that tcg_cur_ctxs gets incremented everytime a vCPU gets
hotplugged but never gets decremented everytime a vCPU gets unplugged, therefore
breaking the assert stating tcg_cur_ctxs < tcg_max_ctxs after a certain amount
of vCPU hotplugs.
Suggested-by: Salil Mehta <salil.mehta@huawei.com>
[SM: Check Things To Do Section,
https://lore.kernel.org/all/20200613213629.21984-1-salil.mehta@huawei.com/]
Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
---
accel/tcg/tcg-accel-ops-mttcg.c | 1 +
include/tcg/tcg.h | 1 +
tcg/tcg.c | 23 +++++++++++++++++++++++
3 files changed, 25 insertions(+)
diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
index b276262007..5cf9747ef2 100644
--- a/accel/tcg/tcg-accel-ops-mttcg.c
+++ b/accel/tcg/tcg-accel-ops-mttcg.c
@@ -127,6 +127,7 @@ static void *mttcg_cpu_thread_fn(void *arg)
qemu_mutex_unlock_iothread();
rcu_remove_force_rcu_notifier(&force_rcu.notifier);
rcu_unregister_thread();
+ tcg_unregister_thread();
return NULL;
}
diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 0875971719..6c1cd2a618 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -785,6 +785,7 @@ static inline void *tcg_malloc(int size)
void tcg_init(size_t tb_size, int splitwx, unsigned max_cpus);
void tcg_register_thread(void);
+void tcg_unregister_thread(void);
void tcg_prologue_init(TCGContext *s);
void tcg_func_start(TCGContext *s);
diff --git a/tcg/tcg.c b/tcg/tcg.c
index ddfe9a96cb..6760f40823 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -742,6 +742,14 @@ static void alloc_tcg_plugin_context(TCGContext *s)
#endif
}
+static void free_tcg_plugin_context(TCGContext *s)
+{
+#ifdef CONFIG_PLUGIN
+ g_ptr_array_unref(s->plugin_tb->insns);
+ g_free(s->plugin_tb);
+#endif
+}
+
/*
* All TCG threads except the parent (i.e. the one that called tcg_context_init
* and registered the target's TCG globals) must register with this function
@@ -791,6 +799,21 @@ void tcg_register_thread(void)
tcg_ctx = s;
}
+
+void tcg_unregister_thread(void)
+{
+ TCGContext *s = tcg_ctx;
+ unsigned int n;
+
+ /* Unclaim an entry in tcg_ctxs */
+ n = qatomic_fetch_dec(&tcg_cur_ctxs);
+ g_assert(n > 1);
+ qatomic_store_release(&tcg_ctxs[n - 1], 0);
+
+ free_tcg_plugin_context(s);
+
+ g_free(s);
+}
#endif /* !CONFIG_USER_ONLY */
/* pool based memory allocation */
--
2.34.1
- [PATCH RFC V2 29/37] arm/virt: Update the guest(via GED) about CPU hot-(un)plug events, (continued)
- [PATCH RFC V2 29/37] arm/virt: Update the guest(via GED) about CPU hot-(un)plug events, Salil Mehta, 2023/09/26
- [PATCH RFC V2 30/37] hw/arm: Changes required for reset and to support next boot, Salil Mehta, 2023/09/26
- [PATCH RFC V2 31/37] physmem, gdbstub: Common helping funcs/changes to *unrealize* vCPU, Salil Mehta, 2023/09/26
- [PATCH RFC V2 32/37] target/arm: Add support of *unrealize* ARMCPU during vCPU Hot-unplug, Salil Mehta, 2023/09/26
- [PATCH RFC V2 35/37] hw/arm: Support hotplug capability check using _OSC method, Salil Mehta, 2023/09/26
- Re: [PATCH RFC V2 35/37] hw/arm: Support hotplug capability check using _OSC method, Gavin Shan, 2023/09/29
- [PATCH RFC V2 36/37] tcg/mttcg: enable threads to unregister in tcg_ctxs[],
Salil Mehta <=
- [PATCH RFC V2 37/37] hw/arm/virt: Expose cold-booted CPUs as MADT GICC Enabled, Salil Mehta, 2023/09/26