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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 26 Oct 2015 09:52:12 +0000
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Subject: Re: [Qemu-devel] [PATCH v4 03/13] target-arm: Add support for
	AArch32 S2 negative t0sz
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To: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>, Alexander Graf <agraf@suse.de>, Sergey Fedorov <serge.fdrv@gmail.com>, Laurent Desnogues <laurent.desnogues@gmail.com>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>

On 26 October 2015 at 09:20, Edgar E. Iglesias
<edgar.iglesias@xilinx.com> wrote:
> Yes, sounds good. I've changed the patch to the following:
>
> @@ -6521,8 +6521,24 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>       */
>      int32_t t0sz = extract32(tcr->raw_tcr, 0, 6);
>      if (va_size == 64) {
> +        /* AArch64 translation.  */
>          t0sz = MIN(t0sz, 39);
>          t0sz = MAX(t0sz, 16);
> +    } else if (mmu_idx != ARMMMUIdx_S2NS) {
> +        /* AArch32 stage 1 translation.  */
> +        t0sz = extract32(t0sz, 0, 3);
> +    } else {
> +        /* AArch32 stage 2 translation.  */
> +        bool sext = extract32(t0sz, 4, 1);
> +        bool sign = extract32(t0sz, 3, 1);
> +        t0sz = sextract32(t0sz, 0, 4);
> +
> +        /* If the sign-extend bit is not the same as t0sz[3], the result
> +         * is unpredictable. Flag this as a guest error.  */
> +        if (sign != sext) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "AArch32: VTCR.S / VTCR.T0SZ[3] missmatch\n");
> +        }
>      }
>

Looks good, but maybe we should just do all the extracts
on tcr->raw_tcr, rather than extracting 6 bits of it and
then re-extracting some subset of bits from that extract
(for the 32-bit stage 1 case in particular it would be
simpler).

-- PMM