From patchwork Sun Sep 10 08:29:02 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Guo Ren X-Patchwork-Id: 13378475 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C63D8EEB57E for ; Sun, 10 Sep 2023 08:31:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346538AbjIJIbY (ORCPT ); Sun, 10 Sep 2023 04:31:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbjIJIbX (ORCPT ); Sun, 10 Sep 2023 04:31:23 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21BA110FB; Sun, 10 Sep 2023 01:30:57 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29D41C433C8; Sun, 10 Sep 2023 08:30:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694334656; bh=b/96e8ctDdPWQM+BjwYA3uNNS7hx8TS7HxYP5gGaMAk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fm0Let9OCBGIoNmVO+tWV2aF3bPlay5iI8Eg7PyWvfi7GFcR5h1ddebm76ADuzdV7 zlubzUhzZnN7ilI1SHCW7LnbefedHejQCfbyv+YDibAe25M1WWhJ9HM9Ygu0MKgpjg PKSfW55K9A1jzU6xGL6jPhfzwTc9IUt0MaV2II6TtCd7IS6usoMlN/ZAWvixkzjOtq rNv5W9HtexkqJSf7hSzpCXV6D7KKxWjve2+8hp9N0bAmWZ4eg3LOdV9hAVxEpYjXJq ERqn1H+ZIRbtVR34pV7D++ZQWT9jRN0vpbpKgjQ8Vr9eBPWd1mHOtDfm7kL9MJO2mb D2Tzp6TLhUQkg== From: guoren@kernel.org To: paul.walmsley@sifive.com, anup@brainfault.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, palmer@rivosinc.com, longman@redhat.com, boqun.feng@gmail.com, tglx@linutronix.de, paulmck@kernel.org, rostedt@goodmis.org, rdunlap@infradead.org, catalin.marinas@arm.com, conor.dooley@microchip.com, xiaoguang.xing@sophgo.com, bjorn@rivosinc.com, alexghiti@rivosinc.com, keescook@chromium.org, greentime.hu@sifive.com, ajones@ventanamicro.com, jszhang@kernel.org, wefu@redhat.com, wuwei2016@iscas.ac.cn, leobras@redhat.com Cc: linux-arch@vger.kernel.org, linux-riscv@lists.infradead.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-csky@vger.kernel.org, Guo Ren , Guo Ren Subject: [PATCH V11 08/17] riscv: qspinlock: Add virt_spin_lock() support for KVM guest Date: Sun, 10 Sep 2023 04:29:02 -0400 Message-Id: <20230910082911.3378782-9-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20230910082911.3378782-1-guoren@kernel.org> References: <20230910082911.3378782-1-guoren@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Guo Ren Add a static key controlling whether virt_spin_lock() should be called or not. When running on bare metal set the new key to false. The KVM guests fall back to a Test-and-Set spinlock, because fair locks have horrible lock 'holder' preemption issues. The virt_spin_lock_key would shortcut for the queued_spin_lock_slowpath() function that allow virt_spin_lock to hijack it. Signed-off-by: Guo Ren Signed-off-by: Guo Ren --- .../admin-guide/kernel-parameters.txt | 4 +++ arch/riscv/include/asm/sbi.h | 8 +++++ arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ arch/riscv/kernel/sbi.c | 2 +- arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- 5 files changed, 64 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 61cacb8dfd0e..f75bedc50e00 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3927,6 +3927,10 @@ no_uaccess_flush [PPC] Don't flush the L1-D cache after accessing user data. + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use + native_queued_spinlock when the nopvspin option is enabled. + This would help vcpu=pcpu scenarios. + novmcoredd [KNL,KDUMP] Disable device dump. Device dump allows drivers to append dump data to vmcore so you can collect driver diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h index 501e06e52078..e0233b3d7a5f 100644 --- a/arch/riscv/include/asm/sbi.h +++ b/arch/riscv/include/asm/sbi.h @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { SBI_EXT_BASE_GET_MIMPID, }; +enum sbi_ext_base_impl_id { + SBI_EXT_BASE_IMPL_ID_BBL = 0, + SBI_EXT_BASE_IMPL_ID_OPENSBI, + SBI_EXT_BASE_IMPL_ID_XVISOR, + SBI_EXT_BASE_IMPL_ID_KVM, +}; + enum sbi_ext_time_fid { SBI_EXT_TIME_SET_TIMER = 0, }; @@ -269,6 +276,7 @@ int sbi_console_getchar(void); long sbi_get_mvendorid(void); long sbi_get_marchid(void); long sbi_get_mimpid(void); +long sbi_get_firmware_id(void); void sbi_set_timer(uint64_t stime_value); void sbi_shutdown(void); void sbi_send_ipi(unsigned int cpu); diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h index 8ea0fee80652..6b38d6616f14 100644 --- a/arch/riscv/include/asm/spinlock.h +++ b/arch/riscv/include/asm/spinlock.h @@ -4,6 +4,28 @@ #define __ASM_RISCV_SPINLOCK_H #ifdef CONFIG_QUEUED_SPINLOCKS +/* + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key + * would shortcut for the queued_spin_lock_slowpath() function that allow + * virt_spin_lock to hijack it. + */ +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); + +#define virt_spin_lock virt_spin_lock +static inline bool virt_spin_lock(struct qspinlock *lock) +{ + if (!static_branch_likely(&virt_spin_lock_key)) + return false; + + do { + while (atomic_read(&lock->val) != 0) + cpu_relax(); + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); + + return true; +} + #define _Q_PENDING_LOOPS (1 << 9) #endif diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c index 88eea3a99ee0..cdd45edc8db4 100644 --- a/arch/riscv/kernel/sbi.c +++ b/arch/riscv/kernel/sbi.c @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); } -static inline long sbi_get_firmware_id(void) +long sbi_get_firmware_id(void) { return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); } diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 0f084f037651..c57d15b05160 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include #include @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); EXPORT_SYMBOL(combo_qspinlock_key); #endif +#ifdef CONFIG_QUEUED_SPINLOCKS +static bool no_virt_spin_key = false; +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); + +static int __init no_virt_spin_setup(char *p) +{ + no_virt_spin_key = true; + + return 0; +} +early_param("no_virt_spin", no_virt_spin_setup); + +static void __init virt_spin_lock_init(void) +{ + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || + no_virt_spin_key) + static_branch_disable(&virt_spin_lock_key); + else + pr_info("Enable virt_spin_lock\n"); +} +#endif + static void __init riscv_spinlock_init(void) { #ifdef CONFIG_RISCV_COMBO_SPINLOCKS - if (!enable_qspinlock_key) { + if (!enable_qspinlock_key && + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { static_branch_disable(&combo_qspinlock_key); pr_info("Ticket spinlock: enabled\n"); } else { pr_info("Queued spinlock: enabled\n"); } #endif + +#ifdef CONFIG_QUEUED_SPINLOCKS + virt_spin_lock_init(); +#endif } extern void __init init_rt_signal_env(void);