Re: [PATCH v2 1/4] KVM: arm64: Forbid kprobing of the VHE world-switch code

From: Marc Zyngier <marc.zyngier@arm.com>
To: James Morse <james.morse@arm.com>, linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Will Deacon <will.deacon@arm.com>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v2 1/4] KVM: arm64: Forbid kprobing of the VHE world-switch code
Date: Fri, 1 Feb 2019 13:34:11 +0000	[thread overview]
Message-ID: <e0b2aac7-f5b0-52c7-b4de-2c31c9b9d19d@arm.com> (raw)
In-Reply-To: <20190124163257.233929-2-james.morse@arm.com>

On 24/01/2019 16:32, James Morse wrote:
> On systems with VHE the kernel and KVM's world-switch code run at the
> same exception level. Code that is only used on a VHE system does not
> need to be annotated as __hyp_text as it can reside anywhere in the
> kernel text.
> 
> __hyp_text was also used to prevent kprobes from patching breakpoint
> instructions into this region, as this code runs at a different
> exception level. While this is no longer true with VHE, KVM still
> switches VBAR_EL1, meaning a kprobe's breakpoint executed in the
> world-switch code will cause a hyp-panic.

[...]

For what it is worth, I've now queued this patch as a fix for 5.0.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...