linux-kernel - Re: [PATCH 5.10 38/58] KVM: arm64: Allow indirect vectors to be used without SPECTRE

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Date:   Fri, 11 Mar 2022 00:48:59 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>
Subject: Re: [PATCH 5.10 38/58] KVM: arm64: Allow indirect vectors to be used
 without SPECTRE_V3A

Hi!

What is going on here?

> commit 5bdf3437603d4af87f9c7f424b0c8aeed2420745 upstream.

Upstream commit 5bdf is very different from this. In particular,

>  arch/arm64/kvm/hyp/smccc_wa.S    |   66 +++++++++++++++++++++++++++++++++++++++

I can't find smccc_wa.S, neither in mainline, nor in -next. And it
looks buggy. I suspect loop_k24 should loop 24 times, but it does 8
loops AFAICT. Same problem with loop_k32.

Best regards,
							Pavel
> --- a/arch/arm64/kvm/hyp/smccc_wa.S
> +++ b/arch/arm64/kvm/hyp/smccc_wa.S
> +
> +	.global	__spectre_bhb_loop_k24
> +SYM_DATA_START(__spectre_bhb_loop_k24)
> +	esb
> +	sub	sp, sp, #(8 * 2)
> +	stp	x0, x1, [sp, #(8 * 0)]
> +	mov	x0, #8
> +2:	b	. + 4
> +	subs	x0, x0, #1
> +	b.ne	2b
> +	dsb	nsh
> +	isb
> +	ldp	x0, x1, [sp, #(8 * 0)]
> +	add	sp, sp, #(8 * 2)
> +1:	.org __spectre_bhb_loop_k24 + __SPECTRE_BHB_LOOP_SZ
> +	.org 1b
> +SYM_DATA_END(__spectre_bhb_loop_k24)
> +
> +	.global	__spectre_bhb_loop_k32
> +SYM_DATA_START(__spectre_bhb_loop_k32)
> +	esb
> +	sub	sp, sp, #(8 * 2)
> +	stp	x0, x1, [sp, #(8 * 0)]
> +	mov	x0, #8
> +2:	b	. + 4
> +	subs	x0, x0, #1
> +	b.ne	2b
> +	dsb	nsh
> +	isb
> +	ldp	x0, x1, [sp, #(8 * 0)]
> +	add	sp, sp, #(8 * 2)
> +1:	.org __spectre_bhb_loop_k32 + __SPECTRE_BHB_LOOP_SZ
> +	.org 1b
> +SYM_DATA_END(__spectre_bhb_loop_k32)
> 

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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