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d="scan'208";a="118253079" From: Andrew Cooper To: Xen-devel CC: Andrew Cooper , Jan Beulich , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Wei Liu , Stefano Stabellini , Julien Grall , Volodymyr Babchuk , Bertrand Marquis , Oleksii Kurochko , Shawn Anastasio , Henry Wang Subject: [PATCH v3 01/10] xen/version: Calculate xen_capabilities_info once at boot Date: Tue, 15 Aug 2023 22:06:41 +0100 Message-ID: <20230815210650.2735671-2-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230815210650.2735671-1-andrew.cooper3@citrix.com> References: <20230815210650.2735671-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 The arch_get_xen_caps() infrastructure is horribly inefficient for something that is constant after features have been resolved on boot. Every instance used snprintf() to format constants into a string (which gets shorter when %d gets resolved!), and which get double buffered on the stack. Switch to using string literals with the "3.0" inserted - these numbers haven't changed in 18 years (The Xen 3.0 release was Dec 5th 2005). Use initcalls to format the data into xen_cap_info, which is deliberately not of type xen_capabilities_info_t because a 1k array is a silly overhead for storing a maximum of 77 chars (the x86 version) and isn't liable to need any more space in the forseeable future. This speeds up the the XENVER_capabilities hypercall, but the purpose of the change is to allow us to introduce a better XENVER_* API that doesn't force the use of a 1k buffer on the stack. Signed-off-by: Andrew Cooper Reviewed-by: Stefano Stabellini Acked-by: Jan Beulich --- CC: Jan Beulich CC: Roger Pau Monné CC: Wei Liu CC: Stefano Stabellini CC: Julien Grall CC: Volodymyr Babchuk CC: Bertrand Marquis CC: Oleksii Kurochko CC: Shawn Anastasio CC: Henry Wang v3: * CC new-arch folks so they're aware v2: * New Moving to __initcall() also allows new architectures to not implement this API, and I'm going to recommend strongly that they dont. Its a very dubious way of signalling about 3 bits of info to the toolstack, and inefficient to use (the toolstack has to do string parsing on the result figure out if PV64/PV32/HVM is available). --- xen/arch/arm/setup.c | 20 +++++++------------- xen/arch/x86/setup.c | 31 ++++++++++--------------------- xen/common/kernel.c | 3 ++- xen/include/xen/hypercall.h | 2 -- xen/include/xen/version.h | 2 ++ 5 files changed, 21 insertions(+), 37 deletions(-) diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c index 44ccea03ca14..3592c9ebc1cd 100644 --- a/xen/arch/arm/setup.c +++ b/xen/arch/arm/setup.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -1286,24 +1287,17 @@ void __init start_xen(unsigned long boot_phys_offset, switch_stack_and_jump(idle_vcpu[0]->arch.cpu_info, init_done); } -void arch_get_xen_caps(xen_capabilities_info_t *info) +static int __init init_xen_cap_info(void) { - /* Interface name is always xen-3.0-* for Xen-3.x. */ - int major = 3, minor = 0; - char s[32]; - - (*info)[0] = '\0'; - #ifdef CONFIG_ARM_64 - snprintf(s, sizeof(s), "xen-%d.%d-aarch64 ", major, minor); - safe_strcat(*info, s); + safe_strcat(xen_cap_info, "xen-3.0-aarch64 "); #endif if ( cpu_has_aarch32 ) - { - snprintf(s, sizeof(s), "xen-%d.%d-armv7l ", major, minor); - safe_strcat(*info, s); - } + safe_strcat(xen_cap_info, "xen-3.0-armv7l "); + + return 0; } +__initcall(init_xen_cap_info); /* * Local variables: diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index 2bfc1fd00f8c..206f0c50a136 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -2049,35 +2049,24 @@ void __init noreturn __start_xen(unsigned long mbi_p) unreachable(); } -void arch_get_xen_caps(xen_capabilities_info_t *info) +static int __init cf_check init_xen_cap_info(void) { - /* Interface name is always xen-3.0-* for Xen-3.x. */ - int major = 3, minor = 0; - char s[32]; - - (*info)[0] = '\0'; - if ( IS_ENABLED(CONFIG_PV) ) { - snprintf(s, sizeof(s), "xen-%d.%d-x86_64 ", major, minor); - safe_strcat(*info, s); + safe_strcat(xen_cap_info, "xen-3.0-x86_64 "); if ( opt_pv32 ) - { - snprintf(s, sizeof(s), "xen-%d.%d-x86_32p ", major, minor); - safe_strcat(*info, s); - } + safe_strcat(xen_cap_info, "xen-3.0-x86_32p "); } if ( hvm_enabled ) - { - snprintf(s, sizeof(s), "hvm-%d.%d-x86_32 ", major, minor); - safe_strcat(*info, s); - snprintf(s, sizeof(s), "hvm-%d.%d-x86_32p ", major, minor); - safe_strcat(*info, s); - snprintf(s, sizeof(s), "hvm-%d.%d-x86_64 ", major, minor); - safe_strcat(*info, s); - } + safe_strcat(xen_cap_info, + "hvm-3.0-x86_32 " + "hvm-3.0-x86_32p " + "hvm-3.0-x86_64 "); + + return 0; } +__initcall(init_xen_cap_info); int __hwdom_init xen_in_range(unsigned long mfn) { diff --git a/xen/common/kernel.c b/xen/common/kernel.c index 52aa28762782..f822480a8ef3 100644 --- a/xen/common/kernel.c +++ b/xen/common/kernel.c @@ -30,6 +30,7 @@ enum system_state system_state = SYS_STATE_early_boot; static xen_commandline_t saved_cmdline; static const char __initconst opt_builtin_cmdline[] = CONFIG_CMDLINE; +char __ro_after_init xen_cap_info[128]; static int assign_integer_param(const struct kernel_param *param, uint64_t val) { @@ -537,7 +538,7 @@ long do_xen_version(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg) memset(info, 0, sizeof(info)); if ( !deny ) - arch_get_xen_caps(&info); + safe_strcpy(info, xen_cap_info); if ( copy_to_guest(arg, info, ARRAY_SIZE(info)) ) return -EFAULT; diff --git a/xen/include/xen/hypercall.h b/xen/include/xen/hypercall.h index f307dfb59760..15b6be6ec818 100644 --- a/xen/include/xen/hypercall.h +++ b/xen/include/xen/hypercall.h @@ -56,6 +56,4 @@ common_vcpu_op(int cmd, struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg); -void arch_get_xen_caps(xen_capabilities_info_t *info); - #endif /* __XEN_HYPERCALL_H__ */ diff --git a/xen/include/xen/version.h b/xen/include/xen/version.h index 93c58773630c..4856ad1b446d 100644 --- a/xen/include/xen/version.h +++ b/xen/include/xen/version.h @@ -19,6 +19,8 @@ const char *xen_deny(void); const char *xen_build_info(void); int xen_build_id(const void **p, unsigned int *len); +extern char xen_cap_info[128]; + #ifdef BUILD_ID void xen_build_init(void); int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,