linux-kernel - Re: [PATCH v15 4/6] KVM: arm64: Set PSTATE.EXLOCK when entering an exception

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: <ac3b2d52-5b24-441b-bcdc-463ae9c78b3d@sirena.org.uk>
Date: Thu, 21 Aug 2025 21:44:21 +0100
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Shuah Khan <shuah@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org, kvmarm@...ts.linux.dev,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v15 4/6] KVM: arm64: Set PSTATE.EXLOCK when entering an
 exception

On Wed, Aug 20, 2025 at 11:02:11PM +0100, Marc Zyngier wrote:
> Mark Brown <broonie@...nel.org> wrote:

> > As per DDI 0487 RWTXBY we need to manage PSTATE.EXLOCK when entering an

> Nit: please use an underscore between the type of a statement and its
> "name", as it makes it a bit more readable (R_WTXBY).

Updated as you request.  I have seen both usages - the non _ version
plays nicer with searching the PDF to find the rules since you can just
copy it directly into a PDF viewer.

> > +	// EL, or to GCSCR_ELx.EXLOCKEN for an exception to the same
> > +	// exception level.  See ARM DDI 0487 RWTXBY, D.1.3.2 in K.a.
> > +	new |= enter_exception64_gcs(vcpu, mode, target_mode);
> > +
> >  	new |= PSR_D_BIT;
> >  	new |= PSR_A_BIT;
> >  	new |= PSR_I_BIT;

> But that's not the only case where we have to deal with EXLOCK, is it?
> What of ERET and its PAuth variants? R_TYTWB says:

> <quote>
> If in AArch64 state, any of the following situations can cause an
> illegal exception return:
> 
> [...]
> 
> - If the Effective value of GCSCR_ELx.EXLOCKEN is 1 and PSTATE.EXLOCK
>   is 0, the execution of an exception return instruction to return to
>   the current Exception level ELx.
> </quote>

> My reading of the spec is that this needs handling.

Am I right in thinking that this handling is needed for the NV case
only?

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)