From nobody Mon Apr 6 16:46:04 2026 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C8F63EFD3F for ; Wed, 18 Mar 2026 19:28:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.54 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773862126; cv=none; b=ROa27ya9igrWuF/chOwCzSRhoLU5DY7iKQrWIqUQ46NFVcFoF4MYhsEBgj9J5ALid2JizlXrFmIzf2Tg3zEolMTslIxMBIno88nMRHf9U5FxNLkwCIOo8wRQXMzZUfLAv/J+aYVxfM6WQBdwZSCXxG998ZDprZLgAnaWIf/KibU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773862126; c=relaxed/simple; bh=ldfZ9pUMnpA62gt1lRWUI5ABJgGgK868fR1jHFFi/Ss=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=TMdDGq7q/waSePlUGwBRnV8Ma7z/UVYZTX1FgHiDgWzN8P1YABKeEhxdEKF2rlWllQ+f3zuIBmrntxfpG3xkX712DMn2vytLILTybDRalzJkFj66IosMqEUC7AXOfTDJ85+B2BhZyzntfxCDa9LVU41Jc2dJ12+AwwCj3S661FE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=K8D9eX/y; arc=none smtp.client-ip=209.85.221.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="K8D9eX/y" Received: by mail-wr1-f54.google.com with SMTP id ffacd0b85a97d-43b4f48c47cso121885f8f.0 for ; Wed, 18 Mar 2026 12:28:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773862124; x=1774466924; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=es7C+aEomwQh9iBHWkp8TlDkFCtFsFHa7yh+in3kY0o=; b=K8D9eX/yps0+exnAs9dh3HnlJ9cOBBpZblGh0psRNdTVGKuhJti3In/eYNwaAXlUU1 uL1ap+NwN9IoQftIm793ymOPBSuJ8R9j/5WxcnGw76t2Y64K1hr4fLX1YONr4VqGzd3I W+jFH/OB2eAg8YUDmY7/oQ9OMbAQJ6jgovqO/dikc9ftomACZS26T68CTxqP1AgH+ZTq +z9b4BoroVMOJ8+z7YS+1dE/NyGdqQQlKLwCq3VP01kqKvwcisp24ppqXvVOLsfyamGD 88yIQmtvGGZmwKq8fsJJJ2e8+/m7lq6R+LmJ6XEJus1lUP7Wyp4L7Lj+b/XZMzQV/lBg RrjQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773862124; x=1774466924; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=es7C+aEomwQh9iBHWkp8TlDkFCtFsFHa7yh+in3kY0o=; b=NWRch9e0+HkPY8UOdj0KJwOTdYR2acOO13l+/2m0W0Hboms0aLC+IaxYjH74gLlioQ rBjp7m2w0ozX+32dhCF45UBK1Re89Au5wyFTPjdBfuN4Re6Uq5kGkho6XWvVYxbUif8x 4SKc+70Sybpmn/7SJVqINPHkEyOrlYZOsEbyB6FDJaNPGpYAUlErqgN4vtx6hRebu485 N1mAYj6MBM8Ak7GNZmEefvQ6CnLWofqCbyX+eTHjAMcq60n2XHWTW+eq6+OfYWDAPloD OiXOCak/mWLFTCo67y+ATTeD2bB0Mf2IG3vMBCQRSXeHtF+fEDMbnAPoCdS75gObfIP4 ikxw== X-Forwarded-Encrypted: i=1; AJvYcCXDqkhbWqz0F9PfSVb9V7R78mOCckdfPuJvjEcQ/1jdvlIKyQgT0T+7AkRkV6nV1bTJSahSBtSCwNtObic=@vger.kernel.org X-Gm-Message-State: AOJu0Yy8F5e2xxu+iY2hrBT+PWfP/y843LpvfaU/Y5Qdag+Ig/wi0tRq h9siJrSusR4hx6MNuFn9LOODLNCzU44rXQgw/DAvF9/5da59H0C5MGih X-Gm-Gg: ATEYQzzE7BfMAaYfzNgZXlLstwrcFa8vF53X1ybf3SQ430OP2FYBvAjhjAZM05yPLKi K+Q3r2SGkHzo0c2/YBfsP85w+482AXE6kewL4XBlfDa4QVt4A8CX5CtnhRRBXpxGHnuIRKqI3jE qigmI2lo3eNsd345kMEncySi7HZ/+WdElYqhjheRz+OWDw7WM0Gm0lIamzrETWCrEiVWJt/pnHe YsQDIAbUDvZT3cR6Y89Hp4kIS7zc5OfWRScqd4KEYKbQoBH4DqGHEZnZakLbCOEwbqudqNPrb4e 974K3HvS/PuhgZa2RXlpWbyXTf0Wmy2W6IbsH2niKqbGb3Sikx8rsjDbndUm5Cl+a+vbyHhGWbx klcvn8v8CqXoNFJ1bVHjfBTVt3KxnKIrXqgL5oPcVKrerO0r5g1yK0bMZRxiBFhTXCGwKiF2TWu yjsTNTnkU+UjP/Q4d5m2iCVePTywXU61jKUov09mILzR91R4Vyll+8+0I1pHX70GFOvqmnHJzTu eygYJcK9dOq0fWrZ+8O1D6hwKhQJ79D1lKT8CmIe3pC X-Received: by 2002:a05:6000:2403:b0:439:cb10:dfcd with SMTP id ffacd0b85a97d-43b527c9e61mr7808607f8f.39.1773862123486; Wed, 18 Mar 2026 12:28:43 -0700 (PDT) Received: from fedora ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43b5189971asm10003450f8f.30.2026.03.18.12.28.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 12:28:43 -0700 (PDT) From: Uros Bizjak To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , David Laight Subject: [PATCH v2] x86/asm: Improve clflush alternatives assembler template Date: Wed, 18 Mar 2026 20:28:22 +0100 Message-ID: <20260318192839.47075-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The inline asm used with alternative_input() specifies the address operand for clflush with the "a" input operand constraint and an explicit "(%[addr])" dereference: "clflush (%[addr])", [addr] "a" (addr) This forces the pointer into %rax and manually encodes the memory operand in the template. Instead, use the %a address operand modifier and relax the constraint from "a" to "r": "clflush %a[addr]", [addr] "r" (addr) This lets the compiler choose the register used for the address and formats the operand as a memory reference. Add a "memory" clobber to ensure the flush is not reordered across memory operations. Signed-off-by: Uros Bizjak Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: David Laight --- v2: Add "memory" clobber to ensure flush is not reordered across memory operations. --- arch/x86/include/asm/mwait.h | 3 ++- arch/x86/kernel/process.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index e4815e15dc9a..644ada6c0b3b 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -116,7 +116,8 @@ static __always_inline void mwait_idle_with_hints(u32 e= ax, u32 ecx) if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test(= )) { const void *addr =3D ¤t_thread_info()->flags; =20 - alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [add= r] "a" (addr)); + alternative_input("", "clflush %a[addr]", X86_BUG_CLFLUSH_MONITOR, + [addr] "r" (addr) : "memory"); __monitor(addr, 0, 0); =20 if (need_resched()) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 4c718f8adc59..63581789f7e7 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -921,7 +921,8 @@ static __cpuidle void mwait_idle(void) if (!current_set_polling_and_test()) { const void *addr =3D ¤t_thread_info()->flags; =20 - alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [add= r] "a" (addr)); + alternative_input("", "clflush %a[addr]", X86_BUG_CLFLUSH_MONITOR, + [addr] "r" (addr) : "memory"); __monitor(addr, 0, 0); if (need_resched()) goto out; --=20 2.53.0