From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CEF11E47DD; Sun, 24 Nov 2024 12:47:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732452459; cv=none; b=gTX49DFerOzmGTne4H9FLze4szNuUrNRZSfuqa/JEmVSioMB3Wk61TlVzDxKu9urIYn6Eb7IIbE/OlzYFimvw5fajKoWZigRGjhsBpH/kZYn+IYwjoDG+tV5VQ/f5w5dV3C6feNF9a0FxAguhgknTPXGXfmKUTcY7IrGMmKOGmE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732452459; c=relaxed/simple; bh=ttCOt0jBDmhYRap4VwYAB2ASolDkL1aMpZHI1JEHGlg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ky2wSeEJifj/WXSJt9sJ98q/l0QUnQuc+yqbktCfQZyGqCrRX5+kG6EeV5ry9o8rKnLljmfFEbuP+MMae1TKdomg/EIS3OywFuipc1oFZR1kbCgeQSaJR9D9Vpb+ZLXdr3a8x4jrvwn9D17R5lfcxYbMi4JWCQmWIlsbvpv4d78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b/3Jwbn0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b/3Jwbn0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10FA6C4CECC; Sun, 24 Nov 2024 12:47:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732452459; bh=ttCOt0jBDmhYRap4VwYAB2ASolDkL1aMpZHI1JEHGlg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b/3Jwbn02kgfVUVjghVk1haCdfCtoo6gGlgcMpQ7W09KBAOg3P+WAT/lBABY6ZNji PN5ZnJscVJOLDgOT1s7K5THsWIWx549v8wAODNaVyD2WWSwr0ddX7GLwbLM+QCEuvJ Wv7tH7PnoXg5GVhW0a69glDiZDTjYrqk273KtCZ4nvXuBnih209jm2VmVKeZJHT+Vp vK671xtiePJnso1FV6UF2urN/3YpjD/HPDevQ6+nnpHN9n90uRQnT/nax6udBHyrwo 2KIHkD8aI7faie/QX9Ql2HBY3Ta8y9Zq3JVB2Ia9onabsZzv615mrUIpV5BQEaeWOx gJz+eMusY0B3Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Thomas Gleixner , John Stultz , Sasha Levin , mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, rdunlap@infradead.org, paulmck@kernel.org Subject: [PATCH AUTOSEL 5.10 2/2] timekeeping: Always check for negative motion Date: Sun, 24 Nov 2024 07:47:31 -0500 Message-ID: <20241124124733.3338551-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241124124733.3338551-1-sashal@kernel.org> References: <20241124124733.3338551-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.230 Content-Transfer-Encoding: 8bit From: Thomas Gleixner [ Upstream commit c163e40af9b2331b2c629fd4ec8b703ed4d4ae39 ] clocksource_delta() has two variants. One with a check for negative motion, which is only selected by x86. This is a historic leftover as this function was previously used in the time getter hot paths. Since 135225a363ae timekeeping_cycles_to_ns() has unconditional protection against this as a by-product of the protection against 64bit math overflow. clocksource_delta() is only used in the clocksource watchdog and in timekeeping_advance(). The extra conditional there is not hurting anyone. Remove the config option and unconditionally prevent negative motion of the readout. Signed-off-by: Thomas Gleixner Acked-by: John Stultz Link: https://lore.kernel.org/all/20241031120328.599430157@linutronix.de Signed-off-by: Sasha Levin --- arch/x86/Kconfig | 1 - kernel/time/Kconfig | 5 ----- kernel/time/timekeeping_internal.h | 7 ------- 3 files changed, 13 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 0c802ade80406..e71101ced756e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -107,7 +107,6 @@ config X86 select ARCH_WANTS_THP_SWAP if X86_64 select BUILDTIME_TABLE_SORT select CLKEVT_I8253 - select CLOCKSOURCE_VALIDATE_LAST_CYCLE select CLOCKSOURCE_WATCHDOG select DCACHE_WORD_ACCESS select EDAC_ATOMIC_SCRUB diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index a09b1d61df6a5..5cbedc0a06efc 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -17,11 +17,6 @@ config ARCH_CLOCKSOURCE_DATA config ARCH_CLOCKSOURCE_INIT bool -# Clocksources require validation of the clocksource against the last -# cycle update - x86/TSC misfeature -config CLOCKSOURCE_VALIDATE_LAST_CYCLE - bool - # Timekeeping vsyscall support config GENERIC_TIME_VSYSCALL bool diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h index 4ca2787d1642e..1d4854d5c386e 100644 --- a/kernel/time/timekeeping_internal.h +++ b/kernel/time/timekeeping_internal.h @@ -15,7 +15,6 @@ extern void tk_debug_account_sleep_time(const struct timespec64 *t); #define tk_debug_account_sleep_time(x) #endif -#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) { u64 ret = (now - last) & mask; @@ -26,12 +25,6 @@ static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) */ return ret & ~(mask >> 1) ? 0 : ret; } -#else -static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) -{ - return (now - last) & mask; -} -#endif /* Semi public for serialization of non timekeeper VDSO updates. */ extern raw_spinlock_t timekeeper_lock; -- 2.43.0