From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
tony.luck@intel.com, ak@linux.intel.com,
tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, kvm@vger.kernel.org,
Alyssa Milburn <alyssa.milburn@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
antonio.gomez.iglesias@linux.intel.com,
Alyssa Milburn <alyssa.milburn@intel.com>
Subject: Re: [PATCH v3 1/6] x86/bugs: Add asm helpers for executing VERW
Date: Wed, 25 Oct 2023 14:49:09 -0700 [thread overview]
Message-ID: <20231025214909.yxcldnporsnicrdi@treble> (raw)
In-Reply-To: <da782a61-e7f6-45fa-88e9-9d974dcc1a87@citrix.com>
On Wed, Oct 25, 2023 at 10:30:52PM +0100, Andrew Cooper wrote:
> On 25/10/2023 10:28 pm, Josh Poimboeuf wrote:
> > On Wed, Oct 25, 2023 at 10:10:41PM +0100, Andrew Cooper wrote:
> >> On 25/10/2023 9:52 pm, Pawan Gupta wrote:
> >>> diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S
> >>> index bfb7bcb362bc..f8ba0c0b6e60 100644
> >>> --- a/arch/x86/entry/entry.S
> >>> +++ b/arch/x86/entry/entry.S
> >>> @@ -20,3 +23,16 @@ SYM_FUNC_END(entry_ibpb)
> >>> EXPORT_SYMBOL_GPL(entry_ibpb);
> >>>
> >>> .popsection
> >>> +
> >>> +.pushsection .entry.text, "ax"
> >>> +
> >>> +.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.
> >>
> >>> +SYM_CODE_END(mds_verw_sel);
> >> Thinking about it, should this really be CODE and not a data entry?
> >>
> >> It lives in .entry.text but it really is data and objtool shouldn't be
> >> writing ORC data for it at all.
> >>
> >> (Not to mention that if it's marked as STT_OBJECT, objdump -d will do
> >> the sensible thing and not even try to disassemble it).
> >>
> >> ~Andrew
> >>
> >> P.S. Please CC on the full series. Far less effort than fishing the
> >> rest off lore.
> > +1 to putting it in .rodata or so.
>
> It's necessarily in .entry.text so it doesn't explode with KPTI active.
Ah, right. In general tooling doesn't take too kindly to putting data
in a text section. But it might be ok.
--
Josh
next prev parent reply other threads:[~2023-10-25 21:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-25 20:52 [PATCH v3 0/6] Delay VERW Pawan Gupta
2023-10-25 20:52 ` [PATCH v3 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-25 21:10 ` Andrew Cooper
2023-10-25 21:28 ` Josh Poimboeuf
2023-10-25 21:30 ` Andrew Cooper
2023-10-25 21:49 ` Josh Poimboeuf [this message]
2023-10-25 22:07 ` Pawan Gupta
2023-10-25 22:13 ` Andrew Cooper
2023-10-27 13:48 ` Pawan Gupta
2023-10-27 14:12 ` Andrew Cooper
2023-10-27 14:24 ` Pawan Gupta
2023-10-26 13:44 ` Nikolay Borisov
2023-10-26 13:58 ` Andrew Cooper
2023-10-25 20:52 ` [PATCH v3 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-26 16:25 ` Nikolay Borisov
2023-10-26 19:29 ` Pawan Gupta
2023-10-26 19:40 ` Dave Hansen
2023-10-26 21:15 ` Pawan Gupta
2023-10-26 22:13 ` Pawan Gupta
2023-10-26 22:17 ` Dave Hansen
2023-10-25 20:53 ` [PATCH v3 3/6] x86/entry_32: " Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-10-26 16:14 ` Nikolay Borisov
2023-10-26 19:07 ` Pawan Gupta
2023-10-26 19:30 ` Sean Christopherson
2023-10-26 20:17 ` Sean Christopherson
2023-10-26 21:27 ` Pawan Gupta
2023-10-26 20:48 ` Pawan Gupta
2023-10-26 21:22 ` Sean Christopherson
2023-10-26 22:03 ` Pawan Gupta
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