Re: [PATCH v2 1/3] KVM: arm64: Only read HPFAR_EL2 when value is architecturally valid

[Marc Zyngier <maz@kernel.org>]

On Wed, 02 Apr 2025 21:17:23 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
> 
> KVM's logic for deciding when HPFAR_EL2 is UNKNOWN doesn't align with
> the architecture. Most notably, KVM assumes HPFAR_EL2 contains the
> faulting IPA even in the case of an SEA.
> 
> Align the logic with the architecture rather than attempting to
> paraphrase it. Additionally, take the opportunity to improve the
> language around ARM erratum #834220 such that it actually describes the
> bug.
> 
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
>  arch/arm64/include/asm/esr.h           | 22 ++++++++++--
>  arch/arm64/kvm/hyp/include/hyp/fault.h | 46 ++++++++++++++++----------
>  2 files changed, 48 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
> index d1b1a33f9a8b..92fb26e90840 100644
> --- a/arch/arm64/include/asm/esr.h
> +++ b/arch/arm64/include/asm/esr.h
> @@ -121,6 +121,15 @@
>  #define ESR_ELx_FSC_SEA_TTW(n)	(0x14 + (n))
>  #define ESR_ELx_FSC_SECC	(0x18)
>  #define ESR_ELx_FSC_SECC_TTW(n)	(0x1c + (n))
> +#define ESR_ELx_FSC_ADDRSZ	(0x00)
> +
> +/*
> + * Annoyingly, the negative levels for Address size faults aren't laid out
> + * contiguously (or in the desired order)
> + */
> +#define ESR_ELx_FSC_ADDRSZ_nL(n)	((n) == -1 ? 0x25 : 0x2C)
> +#define ESR_ELx_FSC_ADDRSZ_L(n)		((n) < 0 ? ESR_ELx_FSC_ADDRSZ_nL(n) : \
> +						   (ESR_ELx_FSC_ADDRSZ + (n)))

Oh gawd, D128 and its level -2. Do we really want to add this now? I'd
rather leave it to whoever already lives in th future. Specially given
that the helper you introduce below doesn't make any use of it.

Otherwise looks OK.

	M.

-- 
Jazz isn't dead. It just smells funny.