1. Patchew
  2. QEMU
  3. [PULL 000/153] Bigger than average pull request for QEMU 11.0
  4. View patch

[PULL 058/153] rust/hpet: Borrow HPETState.regs once in HPETState::post_load()

Paolo Bonzini posted 153 patches 1 week, 4 days ago
Maintainers: "Alex Bennée" <alex.bennee@linaro.org>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Thomas Huth <thuth@redhat.com>, Yonggang Luo <luoyonggang@gmail.com>, Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Cameron Esfahani <dirty@apple.com>, Roman Bolshakov <rbolshakov@ddn.com>, Phil Dennis-Jordan <phil@philjordan.eu>, Mads Ynddal <mads@ynddal.dk>, Magnus Kulke <magnus.kulke@linux.microsoft.com>, Wei Liu <wei.liu@kernel.org>, Stefano Stabellini <sstabellini@kernel.org>, Anthony PERARD <anthony@xenproject.org>, Paul Durrant <paul@xen.org>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, David Hildenbrand <david@kernel.org>, Igor Mammedov <imammedo@redhat.com>, Alistair Francis <alistair.francis@wdc.com>, Stefan Berger <stefanb@linux.vnet.ibm.com>, John Snow <jsnow@redhat.com>, Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>, Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Fam Zheng <fam@euphon.net>, Aarushi Mehta <mehta.aaru20@gmail.com>, Julia Suvorova <jusual@redhat.com>, Stefano Garzarella <sgarzare@redhat.com>, Stefan Weil <sw@weilnetz.de>, Samuel Thibault <samuel.thibault@ens-lyon.org>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, Zhao Liu <zhao1.liu@intel.com>, Peter Maydell <peter.maydell@linaro.org>, Mauro Carvalho Chehab <mchehab+huawei@kernel.org>, "Daniel P. Berrangé" <berrange@redhat.com>, Luc Michel <luc@lmichel.fr>, Damien Hedde <damien.hedde@dahe.fr>, Peter Xu <peterx@redhat.com>, Fabiano Rosas <farosas@suse.de>, Markus Armbruster <armbru@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Ani Sinha <anisinha@redhat.com>, Christian Schoenebeck <qemu_oss@crudebyte.com>, Greg Kurz <groug@kaod.org>, "Michael S. Tsirkin" <mst@redhat.com>, Dongjiu Geng <gengdongjiu1@gmail.com>, Aurelien Jarno <aurelien@aurel32.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, "Cédric Le Goater" <clg@kaod.org>, Steven Lee <steven_lee@aspeedtech.com>, Troy Lee <leetroy@gmail.com>, Jamin Lin <jamin_lin@aspeedtech.com>, Andrew Jeffery <andrew@codeconstruct.com.au>, Joel Stanley <joel@jms.id.au>, Tyrone Ting <kfting@nuvoton.com>, Hao Wu <wuhaotsh@google.com>, Beniamino Galvani <b.galvani@gmail.com>, Strahinja Jankovic <strahinja.p.jankovic@gmail.com>, Niek Linnenbank <nieklinnenbank@gmail.com>, Samuel Tardieu <sam@rfc1149.net>, Antony Pavlov <antonynpavlov@gmail.com>, Igor Mitsyanko <i.mitsyanko@gmail.com>, Jean-Christophe Dubois <jcd@tribudubois.net>, Andrey Smirnov <andrew.smirnov@gmail.com>, Bernhard Beschow <shentey@gmail.com>, Rob Herring <robh@kernel.org>, Subbaraya Sundeep <sundeep.lkml@gmail.com>, Jan Kiszka <jan.kiszka@web.de>, Felipe Balbi <balbi@kernel.org>, Radoslaw Biernacki <rad@semihalf.com>, Leif Lindholm <leif.lindholm@oss.qualcomm.com>, Eric Auger <eric.auger@redhat.com>, Alexandre Iooss <erdnaxe@crans.org>, Shannon Zhao <shannon.zhaosl@gmail.com>, Gerd Hoffmann <kraxel@redhat.com>, Laurent Vivier <laurent@vivier.eu>, Michael Rolnik <mrolnik@gmail.com>, Raphael Norwitz <raphael@enfabrica.net>, Helge Deller <deller@gmx.de>, "Clément Chigot" <chigot@adacore.com>, Frederic Konrad <konrad.frederic@yahoo.fr>, Alberto Garcia <berto@igalia.com>, Yoshinori Sato <yoshinori.sato@nifty.com>, Magnus Damm <magnus.damm@gmail.com>, Palmer Dabbelt <palmer@dabbelt.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>, Halil Pasic <pasic@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Jason Herne <jjherne@linux.ibm.com>, Vijai Kumar K <vijai@behindbytes.com>, Nicholas Piggin <npiggin@gmail.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, "Collin L. Walling" <walling@linux.ibm.com>, Amit Shah <amit@kernel.org>, Yanan Wang <wangyanan55@huawei.com>, Riku Voipio <riku.voipio@iki.fi>, Paul Burton <paulburton@kernel.org>, Aleksandar Rikalo <arikalo@gmail.com>, Jonathan Cameron <jonathan.cameron@huawei.com>, Fan Ni <fan.ni@samsung.com>, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, "Hervé Poussineau" <hpoussin@reactos.org>, BALATON Zoltan <balaton@eik.bme.hu>, Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>, Dmitry Osipenko <dmitry.osipenko@collabora.com>, Dmitry Fleytman <dmitry.fleytman@gmail.com>, Ninad Palsule <ninad@linux.ibm.com>, Glenn Miles <milesg@linux.ibm.com>, "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>, Corey Minyard <cminyard@mvista.com>, Patrick Leis <venture@google.com>, Alejandro Jimenez <alejandro.j.jimenez@oracle.com>, Sairaj Kodilkar <sarunkod@amd.com>, Jason Wang <jasowang@redhat.com>, Yi Liu <yi.l.liu@intel.com>, "Clément Mathieu--Drif" <clement.mathieu--drif@eviden.com>, David Woodhouse <dwmw2@infradead.org>, Sergio Lopez <slp@redhat.com>, Alexander Graf <graf@amazon.com>, Dorjoy Chowdhury <dorjoychy111@gmail.com>, Song Gao <gaosong@loongson.cn>, Bibo Mao <maobibo@loongson.cn>, Jiaxun Yang <jiaxun.yang@flygoat.com>, Huacai Chen <chenhuacai@kernel.org>, Jia Liu <proljc@gmail.com>, Gautam Menghani <gautam@linux.ibm.com>, Aditya Gupta <adityag@linux.ibm.com>, Xiao Guangrong <xiaoguangrong.eric@gmail.com>, Alexander Bulekov <alxndr@bu.edu>, Bandan Das <bsd@redhat.com>, Darren Kenny <darren.kenny@oracle.com>, Qiuhao Li <Qiuhao.Li@outlook.com>, Artyom Tarasenko <atar4qemu@gmail.com>, Gustavo Romero <gustavo.romero@linaro.org>, Francisco Iglesias <francisco.iglesias@amd.com>, Pavel Pisa <pisa@cmp.felk.cvut.cz>, Vikram Garhwal <vikram.garhwal@bytedance.com>, Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>, Max Filippov <jcmvbkbc@gmail.com>, Jiri Pirko <jiri@resnulli.us>, Sven Schnelle <svens@stackframe.org>, Stafford Horne <shorne@gmail.com>, Elena Ufimtseva <elena.ufimtseva@oracle.com>, Jagannathan Raman <jag.raman@oracle.com>, Chinmay Rath <rathc@linux.ibm.com>, Sai Pavan Boddu <sai.pavan.boddu@amd.com>, Ran Wang <wangran@bosc.ac.cn>, Anup Patel <anup.patel@wdc.com>, Eric Farman <farman@linux.ibm.com>, Matthew Rosato <mjrosato@linux.ibm.com>, Ilya Leoshkevich <iii@linux.ibm.com>, Tony Krowiak <akrowiak@linux.ibm.com>, Farhan Ali <alifm@linux.ibm.com>, Nina Schoetterl-Glausch <nsg@linux.ibm.com>, Jared Rossi <jrossi@linux.ibm.com>, Zhuoying Cai <zycai@linux.ibm.com>, Cornelia Huck <cohuck@redhat.com>, Hannes Reinecke <hare@suse.com>, Bin Meng <bmeng.cn@gmail.com>, Titus Rwantare <titusr@google.com>, Bastian Koppelmann <kbastian@mail.uni-paderborn.de>, Jeuk Kim <jeuk20.kim@samsung.com>, "Hongren (Zenithal) Zheng" <i@zenithal.me>, "Canokeys.org" <contact@canokeys.org>, John Levon <john.levon@nutanix.com>, Thanos Makatos <thanos.makatos@nutanix.com>, Alex Williamson <alex@shazbot.org>, Tomita Moeko <tomitamoeko@gmail.com>, Viresh Kumar <viresh.kumar@linaro.org>, Mathieu Poirier <mathieu.poirier@linaro.org>, Manos Pitsidianakis <manos.pitsidianakis@linaro.org>, "Gonglei (Arei)" <arei.gonglei@huawei.com>, Eric Blake <eblake@redhat.com>, Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>, Jesper Devantier <foss@defmacro.it>, Huai-Cheng Kuo <hchkuo@avery-design.com.tw>, Chris Browy <cbrowy@avery-design.com>, Zhenzhong Duan <zhenzhong.duan@intel.com>, "Dr. David Alan Gilbert" <dave@treblig.org>, Zhang Chen <zhangckid@gmail.com>, Li Zhijian <lizhijian@fujitsu.com>, Mahmoud Mandour <ma.mandourr@gmail.com>, Pierrick Bouvier <pierrick.bouvier@linaro.org>, Cleber Rosa <crosa@redhat.com>, Michael Roth <michael.roth@amd.com>, Maksim Davydov <davydov-max@yandex-team.ru>, David Gibson <david@gibson.dropbear.id.au>, Hyman Huang <yong.huang@smartx.com>, Brian Cain <brian.cain@oss.qualcomm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Pedro Barbuda <pbarbuda@microsoft.com>, Mohamed Mediouni <mohamed@unpredictable.fr>, Coiby Xu <Coiby.Xu@gmail.com>
[PULL 058/153] rust/hpet: Borrow HPETState.regs once in HPETState::post_load()
Posted by Paolo Bonzini 1 week, 4 days ago 
From: Zhao Liu <zhao1.liu@intel.com>

Timers in post_load() access the same HPETState, which is the "self"
HPETState.

So there's no need to access HPETState from child HPETTimer again and
again. Instead, just cache and borrow HPETState.regs at the beginning,
and this could save some CPU cycles and reduce borrow() calls.

It's safe, because post_load() is called with BQL protection, so that
there's no other chance to modify the regs.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20251113051937.4017675-15-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/hw/timer/hpet/src/device.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/rust/hw/timer/hpet/src/device.rs b/rust/hw/timer/hpet/src/device.rs
index da938f356e9..abbaebc405e 100644
--- a/rust/hw/timer/hpet/src/device.rs
+++ b/rust/hw/timer/hpet/src/device.rs
@@ -882,9 +882,11 @@ fn pre_save(&self) -> Result<(), migration::Infallible> {
     }
 
     fn post_load(&self, _version_id: u8) -> Result<(), migration::Infallible> {
+        let regs = self.regs.borrow();
+
         for timer in self.timers.iter().take(self.num_timers) {
             let mut t = timer.borrow_mut();
-            let cnt = t.get_state().regs.borrow().counter;
+            let cnt = regs.counter;
 
             t.cmp64 = t.calculate_cmp64(cnt, t.regs.cmp);
             t.last = CLOCK_VIRTUAL.get_ns() - NANOSECONDS_PER_SECOND;
@@ -893,7 +895,7 @@ fn post_load(&self, _version_id: u8) -> Result<(), migration::Infallible> {
         // Recalculate the offset between the main counter and guest time
         if !self.hpet_offset_saved {
             self.hpet_offset
-                .set(ticks_to_ns(self.regs.borrow().counter) - CLOCK_VIRTUAL.get_ns());
+                .set(ticks_to_ns(regs.counter) - CLOCK_VIRTUAL.get_ns());
         }
 
         Ok(())
-- 
2.52.0

Patchew 2.1-devel-b67e4c2

© 2016 - 2026 Red Hat, Inc.