vm-device: support batch update interrupt source group GSI

Split interrupt source group restore into two steps, first restore
the irqfd for each interrupt source entry, and second restore the
GSI routing of the entire interrupt source group.

This patch will reduce restore latency of interrupt source group,
and in a 200-concurrent restore test, the patch reduced the
average IOAPIC restore time from 15ms to 1ms.

Signed-off-by: Yong He <alexyonghe@tencent.com>

devices/src/gic.rs

@@ -98,9 +98,14 @@ impl Gic {
                     i as InterruptIndex,
                     InterruptSourceConfig::LegacyIrq(config),
                     false,
+                    false,
                 )
                 .map_err(Error::EnableInterrupt)?;
         }
+
+        self.interrupt_source_group
+            .set_gsi()
+            .map_err(Error::EnableInterrupt)?;
         Ok(())
     }
 

devices/src/ioapic.rs

@@ -237,9 +237,14 @@ impl Ioapic {
         if state.is_some() {
             for (irq, entry) in ioapic.used_entries.iter().enumerate() {
                 if *entry {
-                    ioapic.update_entry(irq)?;
+                    ioapic.update_entry(irq, false)?;
                 }
             }
+
+            ioapic
+                .interrupt_source_group
+                .set_gsi()
+                .map_err(Error::UpdateInterrupt)?;
         }
 
         Ok(ioapic)
@@ -278,7 +283,7 @@ impl Ioapic {
                 }
                 // The entry must be updated through the interrupt source
                 // group.
-                if let Err(e) = self.update_entry(index) {
+                if let Err(e) = self.update_entry(index, true) {
                     error!("Failed updating IOAPIC entry: {:?}", e);
                 }
                 // Store the information this IRQ is now being used.
@@ -329,7 +334,7 @@ impl Ioapic {
         }
     }
 
-    fn update_entry(&self, irq: usize) -> Result<()> {
+    fn update_entry(&self, irq: usize, set_gsi: bool) -> Result<()> {
         let entry = self.reg_entries[irq];
 
         // Validate Destination Mode value, and retrieve Destination ID
@@ -386,6 +391,7 @@ impl Ioapic {
                 irq as InterruptIndex,
                 InterruptSourceConfig::MsiIrq(config),
                 interrupt_mask(entry) == 1,
+                set_gsi,
             )
             .map_err(Error::UpdateInterrupt)?;
 

devices/src/legacy/gpio_pl061.rs

@@ -361,10 +361,15 @@ mod tests {
             _index: InterruptIndex,
             _config: InterruptSourceConfig,
             _masked: bool,
+            _set_gsi: bool,
         ) -> result::Result<(), std::io::Error> {
             Ok(())
         }
 
+        fn set_gsi(&self) -> result::Result<(), std::io::Error> {
+            Ok(())
+        }
+
         fn notifier(&self, _index: InterruptIndex) -> Option<EventFd> {
             Some(self.event_fd.try_clone().unwrap())
         }

devices/src/legacy/rtc_pl031.rs

@@ -413,10 +413,15 @@ mod tests {
             _index: InterruptIndex,
             _config: InterruptSourceConfig,
             _masked: bool,
+            _set_gsi: bool,
         ) -> result::Result<(), std::io::Error> {
             Ok(())
         }
 
+        fn set_gsi(&self) -> result::Result<(), std::io::Error> {
+            Ok(())
+        }
+
         fn notifier(&self, _index: InterruptIndex) -> Option<EventFd> {
             Some(self.event_fd.try_clone().unwrap())
         }

devices/src/legacy/serial.rs

@@ -365,9 +365,13 @@ mod tests {
             _index: InterruptIndex,
             _config: InterruptSourceConfig,
             _masked: bool,
+            _set_gsi: bool,
         ) -> result::Result<(), std::io::Error> {
             Ok(())
         }
+        fn set_gsi(&self) -> result::Result<(), std::io::Error> {
+            Ok(())
+        }
         fn notifier(&self, _index: InterruptIndex) -> Option<EventFd> {
             Some(self.event_fd.try_clone().unwrap())
         }

devices/src/legacy/uart_pl011.rs

@@ -485,9 +485,13 @@ mod tests {
             _index: InterruptIndex,
             _config: InterruptSourceConfig,
             _masked: bool,
+            _set_gsi: bool,
         ) -> result::Result<(), std::io::Error> {
             Ok(())
         }
+        fn set_gsi(&self) -> result::Result<(), std::io::Error> {
+            Ok(())
+        }
         fn notifier(&self, _index: InterruptIndex) -> Option<EventFd> {
             Some(self.event_fd.try_clone().unwrap())
         }