From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4B33BC88E75 for ; Tue, 15 Sep 2026 12:03:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:To:Subject :MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=KVdxO6hdA6XFoL4rHOKE2J+GKfGaTMxnnC3apsX5p0I=; b=kQVZzBfRRWteMf rFELjHEgxcrjLzn/1qT5PrYzey5zFJUOqel5N2p426vD4NKRBHOf9owBjJaZuXhiPH5AaPY6VFEdq NR506xrgGjgO+HxQN5x9YZoUmtvtGJytN6XX0LfIs87rjZDlrdTeJ06H+0EaxMLu9DLZpuQxmSiDs 8LgPD76ti0lFW8YjaKo9qXDYcFY1rLAufHXggSYG+QKOpUkbKEmRw8iYcvKw0pgFQPk0IxXq7W58d vYxy85Q6dlHrOp9UV/SexVXqIuMMvCLA+TW/jnP396ZCsLgdB3J6y5N+5MqLj4XK+CvHnIWFOmP62 F+uAQfNJkIH5KbQdFUPw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6Rss-00000006NH4-2I2u; Tue, 15 Sep 2026 12:03:34 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6Rsp-00000006NFH-0LgN for linux-arm-kernel@lists.infradead.org; Tue, 15 Sep 2026 12:03:32 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C1827152B; Tue, 15 Sep 2026 05:03:26 -0700 (PDT) Received: from [10.0.152.207] (unknown [10.0.152.207]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 08D0B3F882; Tue, 15 Sep 2026 05:03:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789473810; bh=Ql0vV5t/7oOQyKnU8hNi/eOcAQrT9AGW0rHk2HmA1p8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=aWVZhsYBcnEVi7lPILurGmuO5pisKXymS/AazN08xcogj54Ibm4uDYy+5zHo/HURO 1WiVlMy6pWu9duiOc0MKswdsSRyuYtOd+0SScGItOHl+xwZewCpKoFKhWbQJZp2GGT 5HrCj+5BIZH868RarcLNhjBn+9KDigFUvxK+KD9I= Message-ID: <2adbde95-da5e-4d31-a606-9632b884b313@arm.com> Date: Tue, 15 Sep 2026 13:03:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 17/21] arm64: percpu: Implement preemptible return RMW ops To: Mark Rutland , linux-arm-kernel@lists.infradead.org References: <20260908151741.394589-1-mark.rutland@arm.com> <20260908151741.394589-18-mark.rutland@arm.com> Content-Language: en-GB From: Vladimir Murzin In-Reply-To: <20260908151741.394589-18-mark.rutland@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260915_050331_239856_64B7B36A X-CRM114-Status: GOOD ( 15.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ryan.roberts@arm.com, usama.anjum@arm.com, peterz@infradead.org, catalin.marinas@arm.com, david.laight.linux@gmail.com, stable@vger.kernel.org, ruanjinjie@huawei.com, james.morse@arm.com, yang@os.amperecomputing.com, cl@gentwo.org, maz@kernel.org, david@kernel.org, ljs@kernel.org, will@kernel.org, ardb@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/8/26 16:17, Mark Rutland wrote: > Use the PCPU GPR infrastructure to implement all of the RMW ops which > return a value. > > Test case: > > | u64 outline_this_cpu_add_return_u64(u64 __percpu *p, u64 v) > | { > | return this_cpu_add_return(*p, v); > | } > > Generated code before this patch (v7.2-rc4): > > | : > | paciasp > | stp x29, x30, [sp, #-32]! > | mrs x3, sp_el0 > | mov x29, sp > | ldr w2, [x3, #8] > | add w2, w2, #0x1 > | str w2, [x3, #8] > | mov x2, x0 > | mrs x4, tpidr_el1 > | add x2, x2, x4 > | 1: ldxr x0, [x2] > | add x0, x0, x1 > | stxr w5, x0, [x2] > | cbnz w5, 1b > | ldr x1, [x3, #8] > | sub x1, x1, #0x1 > | str w1, [x3, #8] > | cbz x1, 2f > | ldr x1, [x3, #8] > | cbnz x1, 3f > | 2: str x0, [sp, #24] > | bl 0 > | ldr x0, [sp, #24] > | 3: ldp x29, x30, [sp], #32 > | autiasp > | ret > > Generated code after this patch: > > | : > | mrs x3, sp_el0 > | mov w5, #0x10a0 > | strh w5, [x3, #20] > | mrs x5, tpidr_el1 > | add x4, x0, x5 > | 1: ldxr x2, [x4] > | add x2, x2, x1 > | stxr w6, x2, [x4] > | cbnz w6, 1b > | strh wzr, [x3, #20] > | mov x0, x2 > | ret > > Signed-off-by: Mark Rutland > Tested-by: Muhammad Usama Anjum > Cc: Ada Couprie Diaz > Cc: Ard Biesheuvel > Cc: Catalin Marinas > Cc: James Morse > Cc: Jinjie Ruan > Cc: Marc Zyngier > Cc: Peter Zijlstra > Cc: Vladimir Murzin > Cc: Will Deacon > Cc: Yang Shi > --- > arch/arm64/include/asm/percpu.h | 36 ++++++++++++++++++++++----------- > 1 file changed, 24 insertions(+), 12 deletions(-) > > diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h > index 504a7fefa2015..9fe44d04c871b 100644 > --- a/arch/arm64/include/asm/percpu.h > +++ b/arch/arm64/include/asm/percpu.h > @@ -201,24 +201,36 @@ __percpu_##name##_case_##sz(void __percpu *pcp, unsigned long val) \ > > #define __PERCPU_RET_OP_CASE(w, sfx, name, sz, op_llsc, op_lse) \ > static inline u##sz \ > -__percpu_##name##_return_case_##sz(void *ptr, unsigned long val) \ > +__percpu_##name##_return_case_##sz(void __percpu *pcp, unsigned long val) \ > { \ > + u16 *gprs = ¤t_thread_info()->pcpu_gprs; \ > + unsigned long addr; \ > + unsigned long off; \ > unsigned int loop; \ > u##sz ret; \ > \ > - asm volatile (ARM64_LSE_ATOMIC_INSN( \ > + asm volatile ( \ > + __PCPU_GPRS_BEGIN("%[gprs]", "%[pcp]", "%[off]", "%[addr]") \ > + ARM64_LSE_ATOMIC_INSN( \ > /* LL/SC */ \ > - "1: ldxr" #sfx "\t%" #w "[ret], %[ptr]\n" \ > + "1: ldxr" #sfx "\t%" #w "[ret], [%[addr]]\n" \ > #op_llsc "\t%" #w "[ret], %" #w "[ret], %" #w "[val]\n" \ > - " stxr" #sfx "\t%w[loop], %" #w "[ret], %[ptr]\n" \ > + " stxr" #sfx "\t%w[loop], %" #w "[ret], [%[addr]]\n" \ > " cbnz %w[loop], 1b", \ > /* LSE atomics */ \ > - #op_lse #sfx "\t%" #w "[val], %" #w "[ret], %[ptr]\n" \ > + #op_lse #sfx "\t%" #w "[val], %" #w "[ret], [%[addr]]\n"\ > #op_llsc "\t%" #w "[ret], %" #w "[ret], %" #w "[val]\n" \ > __nops(2)) \ > - : [loop] "=&r" (loop), [ret] "=&r" (ret), \ > - [ptr] "+Q"(*(u##sz *)ptr) \ > - : [val] "r" ((u##sz)(val))); \ > + __PCPU_GPRS_END("%[gprs]") \ > + : [gprs] "=Qo" (*gprs), \ > + [addr] "=&r" (addr), \ > + [off] "=&r" (off), \ > + [loop] "=&r" (loop), \ > + [ret] "=&r" (ret) \ > + : [pcp] "r" (pcp), \ > + [val] "r" ((u##sz)(val)) \ > + : "memory" \ > + ); \ > \ > return ret; \ > } > @@ -322,13 +334,13 @@ PERCPU_RET_OP(add, add, ldadd) > _pcp_wrap(__percpu_add_case_64, pcp, val) > > #define this_cpu_add_return_1(pcp, val) \ > - _pcp_protect_return(__percpu_add_return_case_8, pcp, val) > + _pcp_wrap_return(__percpu_add_return_case_8, pcp, val) > #define this_cpu_add_return_2(pcp, val) \ > - _pcp_protect_return(__percpu_add_return_case_16, pcp, val) > + _pcp_wrap_return(__percpu_add_return_case_16, pcp, val) > #define this_cpu_add_return_4(pcp, val) \ > - _pcp_protect_return(__percpu_add_return_case_32, pcp, val) > + _pcp_wrap_return(__percpu_add_return_case_32, pcp, val) > #define this_cpu_add_return_8(pcp, val) \ > - _pcp_protect_return(__percpu_add_return_case_64, pcp, val) > + _pcp_wrap_return(__percpu_add_return_case_64, pcp, val) > > #define this_cpu_and_1(pcp, val) \ > _pcp_wrap(__percpu_andnot_case_8, pcp, ~(u8)(val)) > -- 2.30.2 > FWIW, Reviewed-by: Vladimir Murzin