linux-kernel - Re: [RFC PATCH v1 10/15] KVM: VMX: Use WRMSRNS or its immediate form when available

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250331203811.GCZ-r9M9Zrww_b7IjJ@fat_crate.local>
Date: Mon, 31 Mar 2025 22:38:11 +0200
From: Borislav Petkov <bp@...en8.de>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: "Xin Li (Intel)" <xin@...or.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, linux-hyperv@...r.kernel.org,
	virtualization@...ts.linux.dev, linux-edac@...r.kernel.org,
	kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
	linux-ide@...r.kernel.org, linux-pm@...r.kernel.org,
	bpf@...r.kernel.org, llvm@...ts.linux.dev, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
	hpa@...or.com, jgross@...e.com, andrew.cooper3@...rix.com,
	peterz@...radead.org, acme@...nel.org, namhyung@...nel.org,
	mark.rutland@....com, alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, wei.liu@...nel.org,
	ajay.kaher@...adcom.com, alexey.amakhalov@...adcom.com,
	bcm-kernel-feedback-list@...adcom.com, tony.luck@...el.com,
	pbonzini@...hat.com, vkuznets@...hat.com, seanjc@...gle.com,
	luto@...nel.org, boris.ostrovsky@...cle.com, kys@...rosoft.com,
	haiyangz@...rosoft.com, decui@...rosoft.com
Subject: Re: [RFC PATCH v1 10/15] KVM: VMX: Use WRMSRNS or its immediate form
 when available

On Mon, Mar 31, 2025 at 04:27:23PM -0400, Konrad Rzeszutek Wilk wrote:
> Is that the right path forward?
> 
> That is replace the MSR write to disable speculative execution with a
> non-serialized WRMSR? Doesn't that mean the WRMSRNS is speculative?

Ha, interesting question.

If the WRMSR is non-serializing, when do speculative things like indirect
branches and the like get *actually* cleared and can such a speculation window
be used to leak branch data even if IBRS is actually enabled for example...

Fun.

This change needs to be run by hw folks and I guess until then WRMSRNS should
not get anywhere near mitigation MSRs like SPEC_CTRL or PRED_CMD...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette