linux-kernel - Re: [PATCH v3 1/6] x86/bugs: Add asm helpers for executing VERW

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Message-ID: <20231025220735.gpopnng76klkbuu3@desk>
Date:   Wed, 25 Oct 2023 15:07:35 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Andrew Cooper <andrew.cooper3@...rix.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, tony.luck@...el.com,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        antonio.gomez.iglesias@...ux.intel.com,
        Alyssa Milburn <alyssa.milburn@...el.com>
Subject: Re: [PATCH v3 1/6] x86/bugs: Add asm helpers for executing VERW

On Wed, Oct 25, 2023 at 10:10:41PM +0100, Andrew Cooper wrote:
> > +.align L1_CACHE_BYTES, 0xcc
> > +SYM_CODE_START_NOALIGN(mds_verw_sel)
> > +	UNWIND_HINT_UNDEFINED
> > +	ANNOTATE_NOENDBR
> > +	.word __KERNEL_DS
> 
> You need another .align here.  Otherwise subsequent code will still
> start in this cacheline and defeat the purpose of trying to keep it
> separate.

Right.

> > +SYM_CODE_END(mds_verw_sel);
> 
> Thinking about it, should this really be CODE and not a data entry?

Would that require adding a data equivalent of .entry.text and update
KPTI to keep it mapped? Or is there an easier option?

> P.S. Please CC on the full series.  Far less effort than fishing the
> rest off lore.

I didn't realize get_maintainer.pl isn't doing that already. Proposing
below update to MAINTAINERS:

---
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Date: Wed, 25 Oct 2023 14:50:41 -0700
Subject: [PATCH] MAINTAINERS: Update entry for X86 HARDWARE VULNERABILITIES

Add Andrew Cooper to maintainers of hardware vulnerabilities
mitigations.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 2894f0777537..bf8c8707b8f8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23382,6 +23382,7 @@ M:	Thomas Gleixner <tglx@...utronix.de>
 M:	Borislav Petkov <bp@...en8.de>
 M:	Peter Zijlstra <peterz@...radead.org>
 M:	Josh Poimboeuf <jpoimboe@...nel.org>
+M:	Andrew Cooper <andrew.cooper3@...rix.com>
 R:	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
 S:	Maintained
 F:	Documentation/admin-guide/hw-vuln/
-- 
2.34.1