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Peter Anvin" , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Paolo Bonzini , Vitaly Kuznetsov , Boris Ostrovsky , xen-devel@lists.xenproject.org Subject: [PATCH v2 1/5] x86/paravirt: Replace io_delay() hook with a bool Date: Tue, 16 Dec 2025 14:41:45 +0100 Message-ID: <20251216134150.2710-2-jgross@suse.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251216134150.2710-1-jgross@suse.com> References: <20251216134150.2710-1-jgross@suse.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-6.80 / 50.00]; REPLY(-4.00)[]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-0.989]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[17]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; R_RATELIMIT(0.00)[to_ip_from(RLfdszjqhz8kzzb9uwpzdm8png)]; TO_DN_SOME(0.00)[]; RCVD_TLS_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:mid,suse.com:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Level: X-Spam-Flag: NO X-Spam-Score: -6.80 The io_delay() paravirt hook is in no way performance critical and all users setting it to a different function than native_io_delay() are using an empty function as replacement. This enables to replace the hook with a bool indicating whether native_io_delay() should be called. Signed-off-by: Juergen Gross --- arch/x86/include/asm/io.h | 7 +++++-- arch/x86/include/asm/paravirt.h | 11 +---------- arch/x86/include/asm/paravirt_types.h | 3 +-- arch/x86/kernel/cpu/vmware.c | 2 +- arch/x86/kernel/kvm.c | 8 +------- arch/x86/kernel/paravirt.c | 3 +-- arch/x86/xen/enlighten_pv.c | 6 +----- 7 files changed, 11 insertions(+), 29 deletions(-) diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index ca309a3227c7..0448575569b9 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -245,9 +245,14 @@ extern void io_delay_init(void); #if defined(CONFIG_PARAVIRT) #include #else +#define call_io_delay() true +#endif static inline void slow_down_io(void) { + if (!call_io_delay()) + return; + native_io_delay(); #ifdef REALLY_SLOW_IO native_io_delay(); @@ -256,8 +261,6 @@ static inline void slow_down_io(void) #endif } -#endif - #define BUILDIO(bwl, type) \ static inline void out##bwl##_p(type value, u16 port) \ { \ diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index b5e59a7ba0d0..0ab798d234cc 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -53,16 +53,7 @@ static inline u64 paravirt_steal_clock(int cpu) void __init paravirt_set_cap(void); #endif -/* The paravirtualized I/O functions */ -static inline void slow_down_io(void) -{ - PVOP_VCALL0(cpu.io_delay); -#ifdef REALLY_SLOW_IO - PVOP_VCALL0(cpu.io_delay); - PVOP_VCALL0(cpu.io_delay); - PVOP_VCALL0(cpu.io_delay); -#endif -} +#define call_io_delay() pv_info.io_delay void native_flush_tlb_local(void); void native_flush_tlb_global(void); diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 3502939415ad..b4c15856eab5 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -36,6 +36,7 @@ struct pv_info { #ifdef CONFIG_PARAVIRT_XXL u16 extra_user_64bit_cs; /* __USER_CS if none */ #endif + bool io_delay; const char *name; }; @@ -51,8 +52,6 @@ struct pv_lazy_ops { struct pv_cpu_ops { /* hooks for various privileged instructions */ - void (*io_delay)(void); - #ifdef CONFIG_PARAVIRT_XXL unsigned long (*get_debugreg)(int regno); void (*set_debugreg)(int regno, unsigned long value); diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c index cb3f900c46fc..47db25d63c8d 100644 --- a/arch/x86/kernel/cpu/vmware.c +++ b/arch/x86/kernel/cpu/vmware.c @@ -338,7 +338,7 @@ arch_initcall(activate_jump_labels); static void __init vmware_paravirt_ops_setup(void) { pv_info.name = "VMware hypervisor"; - pv_ops.cpu.io_delay = paravirt_nop; + pv_info.io_delay = false; if (vmware_tsc_khz == 0) return; diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index df78ddee0abb..24e403cdce69 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -74,12 +74,6 @@ DEFINE_PER_CPU_DECRYPTED(struct kvm_steal_time, steal_time) __aligned(64) __visi static int has_steal_clock = 0; static int has_guest_poll = 0; -/* - * No need for any "IO delay" on KVM - */ -static void kvm_io_delay(void) -{ -} #define KVM_TASK_SLEEP_HASHBITS 8 #define KVM_TASK_SLEEP_HASHSIZE (1<