From nobody Mon Apr 6 21:55:28 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5AD6FC6FA82 for ; Fri, 2 Sep 2022 21:38:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231220AbiIBViI (ORCPT ); Fri, 2 Sep 2022 17:38:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231204AbiIBVh7 (ORCPT ); Fri, 2 Sep 2022 17:37:59 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA50EF5CCF for ; Fri, 2 Sep 2022 14:37:57 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id a19-20020aa780d3000000b0052bccd363f8so1610934pfn.22 for ; Fri, 02 Sep 2022 14:37:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date; bh=HDZJ0lSRQoma7HASH55s+Lq3/kCI0PVAr3SKG55mmDE=; b=rBbZGj2hyaPbBdrQ8ZAtAd8fBVTk/aNT+PMfh4D+6g9Dnr1lJ+8WgvE2JpQSQ5mpKr LT2dmPZTqjjH4ka2YE7gNLcVOQ7eD+OWNfyQ2AkU6DMz3lRStI2yu9n2MfIPoTx7L5ey +2YIepUmQxsASZ4ckcGjskYeuPdVvt1j/Wcq+jPORMIzjcCPcV4PD0zHxpxeC1Oq2wre +8hAszoekk7kAiAJsqgWbZ2ymL+wkxPxV5ctB6USiI8NBgGNkPygEfA6Bm89F2jwk/eS piZC+qd+beRl05PxC+rpuQfD/8nEToe3qBGP0kiN2/ERGnRCwcAREuiF7Yu7Hu4WltFr fYMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date; bh=HDZJ0lSRQoma7HASH55s+Lq3/kCI0PVAr3SKG55mmDE=; b=Kn+G9Q0suaGh6iGYP2regRgsv17jpE5UcnanBRA2vj14oscQF2q8p9D319i7DQDO13 fSzltOHqLAkbPYQ/3tLE0KKbFAG02ImLgaPRv6CYct2xJnKiinQybE1OnmnCFZ0ZElrj COzum8crtIXP8ZFaTkj8r4mtm0H/VXi+oNFhnTCQvpw4hMq7EipYTjaxSBcG7H53W3WC 4PDB9xaLvCK+F7ZOdrjRFbFTOPbDBzFzzNciNyVEngrodQIN9PoYKXoHcMrz0p+rIYX3 dRXIL7G9kYAzBBVlaB+EyhXOjwMKq+O6qtRbV9Icjy9xnoqVxFytIGWR7v3Nfuto3VYO cjhA== X-Gm-Message-State: ACgBeo2/ACkx4ewNzLFjek5eb8g6EFQfjQ8Td1ZHCURjlV/ktarcng/F 6xAoQahGDfHIDB02I0mH00kIN5Bi X-Google-Smtp-Source: AA6agR6rg/qLo+yQa1/A/MnMpENNlMrew4RjKFVFUDSg5m3sigIjZqHtxPyD4LsEch28EwHGn9DhXIq91Q== X-Received: from fawn.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5795]) (user=morbo job=sendgmr) by 2002:a17:90b:264a:b0:1fd:f88d:dbad with SMTP id pa10-20020a17090b264a00b001fdf88ddbadmr7040192pjb.93.1662154677243; Fri, 02 Sep 2022 14:37:57 -0700 (PDT) Date: Fri, 2 Sep 2022 21:37:50 +0000 In-Reply-To: <20220902213750.1124421-1-morbo@google.com> Mime-Version: 1.0 References: <20220902213750.1124421-1-morbo@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220902213750.1124421-3-morbo@google.com> Subject: [PATCH 2/2] x86/paravirt: add extra clobbers with ZERO_CALL_USED_REGS enabled From: Bill Wendling To: Juergen Gross , "Srivatsa S. Bhat (VMware)" , Alexey Makhalov , VMware PV-Drivers Reviewers , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Nathan Chancellor , Nick Desaulniers , llvm@lists.linux.dev Cc: Bill Wendling Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The ZERO_CALL_USED_REGS feature may zero out caller-saved registers before returning. In spurious_kernel_fault(), the "pte_offset_kernel()" call results in this assembly code: .Ltmp151: #APP # ALT: oldnstr .Ltmp152: .Ltmp153: .Ltmp154: .section .discard.retpoline_safe,"",@progbits .quad .Ltmp154 .text callq *pv_ops+536(%rip) .Ltmp155: .section .parainstructions,"a",@progbits .p2align 3, 0x0 .quad .Ltmp153 .byte 67 .byte .Ltmp155-.Ltmp153 .short 1 .text .Ltmp156: # ALT: padding .zero (-(((.Ltmp157-.Ltmp158)-(.Ltmp156-.Ltmp152))>0))*((.Ltmp157= -.Ltmp158)-(.Ltmp156-.Ltmp152)),144 .Ltmp159: .section .altinstructions,"a",@progbits .Ltmp160: .long .Ltmp152-.Ltmp160 .Ltmp161: .long .Ltmp158-.Ltmp161 .short 33040 .byte .Ltmp159-.Ltmp152 .byte .Ltmp157-.Ltmp158 .text .section .altinstr_replacement,"ax",@progbits # ALT: replacement 1 .Ltmp158: movq %rdi, %rax .Ltmp157: .text #NO_APP .Ltmp162: testb $-128, %dil The "testb" here is using %dil, but the %rdi register was cleared before returning from "callq *pv_ops+536(%rip)". Adding the proper constraints results in the use of a different register: movq %r11, %rdi # Similar to above. testb $-128, %r11b Link: https://github.com/KSPP/linux/issues/192 Signed-off-by: Bill Wendling Reported-and-tested-by: Nathan Chancellor --- arch/x86/include/asm/paravirt_types.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/p= aravirt_types.h index f04157456a49..b1ab5d94881b 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -414,8 +414,17 @@ int paravirt_disable_iospace(void); "=3Dc" (__ecx) #define PVOP_CALL_CLOBBERS PVOP_VCALL_CLOBBERS, "=3Da" (__eax) =20 -/* void functions are still allowed [re]ax for scratch */ +/* + * void functions are still allowed [re]ax for scratch. + * + * The ZERO_CALL_USED REGS feature may end up zeroing out callee-saved + * registers. Make sure we model this with the appropriate clobbers. + */ +#ifdef CONFIG_ZERO_CALL_USED_REGS +#define PVOP_VCALLEE_CLOBBERS "=3Da" (__eax), PVOP_VCALL_CLOBBERS +#else #define PVOP_VCALLEE_CLOBBERS "=3Da" (__eax) +#endif #define PVOP_CALLEE_CLOBBERS PVOP_VCALLEE_CLOBBERS =20 #define EXTRA_CLOBBERS , "r8", "r9", "r10", "r11" --=20 2.37.2.789.g6183377224-goog