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: Tue, 22 Aug 2023 07:54:52 +0200 [thread overview]
Message-ID: <20230822055452.GDZORNrNdYc3OmGygU@fat_crate.local> (raw)
In-Reply-To: <20230821163649.dyhxdeewlf6eerda@treble>
On Mon, Aug 21, 2023 at 09:36:49AM -0700, Josh Poimboeuf wrote:
> Hm? How exactly is this overriding the retbleed IBPB mitigation?
Sorry, clearly -ETOOMANYMITIGATIONS.
I meant the spectre_v2_user thing which does
indirect_branch_prediction_barrier() based on X86_FEATURE_USE_IBPB.
indirect_branch_prediction_barrier() uses x86_pred_cmd to select which
MSR bits to set and it is initialized by default to PRED_CMD_IBPB.
If you goto pred_cmd, you will overwrite it with PRED_CMD_SBPB here.
I think it should not overwrite it and simply return like before.
Meaning: if SRSO mitigation is off but the spectre_v2_user isn't so you
get what you want.
If you do mitigations=off - which is what most use cases do when they
don't care about mitigations - then it'll work too.
I don't see a sensible use case where user->user spectre_v2 is enabled
but SRSO is off. Maybe there is...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-08-22 5:54 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 [this message]
2023-08-22 6:07 ` Borislav Petkov
2023-08-22 21:59 ` Josh Poimboeuf
2023-08-23 1:27 ` Borislav Petkov
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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