linux-kernel - Re: [PATCH v3 00/20] SRSO fixes/cleanups

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Message-ID: <ZPb8we3RAespXmXI@gmail.com>
Date:   Tue, 5 Sep 2023 12:02:41 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Babu Moger <babu.moger@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, David.Kaplan@....com,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        gregkh@...uxfoundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 00/20] SRSO fixes/cleanups


* Borislav Petkov <bp@...en8.de> wrote:

> On Mon, Sep 04, 2023 at 10:04:44PM -0700, Josh Poimboeuf wrote:
> > v3:
> > - drop kvm patches (to be picked up by Sean)
> > - fix "no microcode, no microcode" printk
> > - fix "Safe Ret" capitalization in documentation
> > - fix chopped line in commit log
> > - drop "x86/srso: Remove redundant X86_FEATURE_ENTRY_IBPB check" patch
> > 
> > Josh Poimboeuf (20):
> >   x86/srso: Fix srso_show_state() side effect
> >   x86/srso: Set CPUID feature bits independently of bug or mitigation
> >     status
> >   x86/srso: Don't probe microcode in a guest
> >   x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
> >   x86/srso: Fix SBPB enablement for (possible) future fixed HW
> >   x86/srso: Print actual mitigation if requested mitigation isn't
> >     possible
> >   x86/srso: Print mitigation for retbleed IBPB case
> >   x86/srso: Fix vulnerability reporting for missing microcode
> >   x86/srso: Fix unret validation dependencies
> >   x86/alternatives: Remove faulty optimization
> >   x86/srso: Improve i-cache locality for alias mitigation
> >   x86/srso: Unexport untraining functions
> >   x86/srso: Remove 'pred_cmd' label
> >   x86/bugs: Remove default case for fully switched enums
> >   x86/srso: Move retbleed IBPB check into existing 'has_microcode' code
> >     block
> >   x86/srso: Disentangle rethunk-dependent options
> >   x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
> >   x86/retpoline: Remove .text..__x86.return_thunk section
> >   x86/nospec: Refactor UNTRAIN_RET[_*]
> >   x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
> > 
> >  Documentation/admin-guide/hw-vuln/srso.rst |  24 ++-
> >  arch/x86/include/asm/nospec-branch.h       |  69 ++++-----
> >  arch/x86/include/asm/processor.h           |   2 -
> >  arch/x86/kernel/alternative.c              |   8 -
> >  arch/x86/kernel/cpu/amd.c                  |  28 ++--
> >  arch/x86/kernel/cpu/bugs.c                 | 102 ++++++------
> >  arch/x86/kernel/vmlinux.lds.S              |  10 +-
> >  arch/x86/lib/retpoline.S                   | 171 +++++++++++----------
> >  include/linux/objtool.h                    |   3 +-
> >  scripts/Makefile.vmlinux_o                 |   3 +-
> >  10 files changed, 201 insertions(+), 219 deletions(-)
> 
> They all look good to me, thanks!
> 
> Acked-by: Borislav Petkov (AMD) <bp@...en8.de>

I've applied them to tip:x86/bugs, thanks guys!

Below is the delta diff from v2 to v3.

Thanks,

	Ingo

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index 4516719e00b5..e715bfc09879 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -57,7 +57,7 @@ The possible values in this file are:
 
  * 'Vulnerable: Safe RET, no microcode':
 
-   The "Safe Ret" mitigation (see below) has been applied to protect the
+   The "Safe RET" mitigation (see below) has been applied to protect the
    kernel, but the IBPB-extending microcode has not been applied.  User
    space tasks may still be vulnerable.
 
@@ -139,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d538043c776d..016a32613259 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2494,7 +2494,7 @@ static void __init srso_select_mitigation(void)
 
 	case SRSO_CMD_IBPB_ON_VMEXIT:
 		if (IS_ENABLED(CONFIG_CPU_SRSO)) {
-			if (has_microcode) {
+			if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) {
 				setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT);
 				srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT;
 			}
@@ -2505,7 +2505,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 }
 
 #undef pr_fmt