From: Borislav Petkov <bp@alien8.de>
To: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Babu Moger <babu.moger@amd.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
David.Kaplan@amd.com, Andrew Cooper <andrew.cooper3@citrix.com>,
Nikolay Borisov <nik.borisov@suse.com>,
gregkh@linuxfoundation.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 04/22] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
Date: Wed, 23 Aug 2023 03:27:28 +0200 [thread overview]
Message-ID: <20230823012728.GCZOVggFCpKiTgqffx@fat_crate.local> (raw)
In-Reply-To: <20230822215901.nkikxpcmlrssi42l@treble>
On Tue, Aug 22, 2023 at 02:59:01PM -0700, Josh Poimboeuf wrote:
> Yeah, I had seen that. The combination of spectre_v2_user=on with
> srso=off doesn't make a whole lot of sense, but... give the user what
> they want and all. Which would presumably be IBPB *without* the SRSO
> mitigation (aka SBPB).
Right.
> I don't think we need to worry about that, SBPB is >= fam19 but retbleed
> is <= fam17. So either way (0x17 or 0x19) entry_ibpb() should do IBPB.
Right, and SBPB is possible only on family => 0x19 anyway which is not
affected by retbleed.
I was worried that we might open some mitigation hole with the overwrite
but it seems we're fine:
family 0x17: retbleed=ibpb, srso=off - is fine, can't do SBPB anyway
family 0x19: retbleed=ibpb, srso=off - fine too, not affected by retbleed, can do SBPB
Unless I'm missing something again which is very likely, by now. ;-\
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-08-23 1:27 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-21 1:18 [PATCH 00/22] SRSO fixes/cleanups Josh Poimboeuf
2023-08-21 1:18 ` [PATCH 01/22] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
2023-08-21 5:42 ` Nikolay Borisov
2023-08-21 6:04 ` Borislav Petkov
2023-08-21 16:17 ` Josh Poimboeuf
2023-08-22 5:23 ` Borislav Petkov
2023-08-21 1:18 ` [PATCH 02/22] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
2023-08-21 5:42 ` Nikolay Borisov
2023-08-21 9:27 ` Andrew Cooper
2023-08-21 14:06 ` Borislav Petkov
2023-08-23 5:20 ` Borislav Petkov
2023-08-23 12:22 ` Andrew Cooper
2023-08-24 4:24 ` Borislav Petkov
2023-08-24 22:04 ` Josh Poimboeuf
2023-08-25 6:42 ` Borislav Petkov
2023-08-21 13:59 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 03/22] KVM: x86: Support IBPB_BRTYPE and SBPB Josh Poimboeuf
2023-08-21 9:34 ` Andrew Cooper
2023-08-21 16:23 ` Josh Poimboeuf
2023-08-21 16:35 ` Sean Christopherson
2023-08-21 16:46 ` Nikolay Borisov
2023-08-21 16:50 ` Sean Christopherson
2023-08-21 17:05 ` Josh Poimboeuf
2023-08-24 16:39 ` Sean Christopherson
2023-08-24 17:07 ` Josh Poimboeuf
2023-08-21 16:49 ` Sean Christopherson
2023-08-21 1:19 ` [PATCH 04/22] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
2023-08-21 14:16 ` Borislav Petkov
2023-08-21 16:36 ` Josh Poimboeuf
2023-08-22 5:54 ` Borislav Petkov
2023-08-22 6:07 ` Borislav Petkov
2023-08-22 21:59 ` Josh Poimboeuf
2023-08-23 1:27 ` Borislav Petkov [this message]
2023-08-21 1:19 ` [PATCH 05/22] x86/srso: Fix SBPB enablement for mitigations=off Josh Poimboeuf
2023-08-23 5:57 ` Borislav Petkov
2023-08-23 20:55 ` Josh Poimboeuf
2023-08-23 23:02 ` Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 06/22] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
2023-08-23 6:06 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 07/22] x86/srso: Remove default case in srso_select_mitigation() Josh Poimboeuf
2023-08-23 6:18 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 08/22] x86/srso: Downgrade retbleed IBPB warning to informational message Josh Poimboeuf
2023-08-24 4:43 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 09/22] x86/srso: Simplify exit paths Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 10/22] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
2023-08-24 4:48 ` Borislav Petkov
2023-08-24 21:40 ` Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 11/22] x86/srso: Slight simplification Josh Poimboeuf
2023-08-24 4:55 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 12/22] x86/srso: Remove redundant X86_FEATURE_ENTRY_IBPB check Josh Poimboeuf
2023-08-25 7:09 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 13/22] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
2023-08-25 7:25 ` Borislav Petkov
2023-08-21 1:19 ` [PATCH 14/22] x86/srso: Fix unret validation dependencies Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 15/22] x86/alternatives: Remove faulty optimization Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 16/22] x86/srso: Unexport untraining functions Josh Poimboeuf
2023-08-21 5:50 ` Nikolay Borisov
2023-08-21 1:19 ` [PATCH 17/22] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 18/22] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 19/22] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 20/22] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 21/22] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
2023-08-21 1:19 ` [PATCH 22/22] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
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