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From: Laurent Desnogues <laurent.desnogues@gmail.com>
Date: Wed, 23 May 2018 08:49:01 +0200
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Subject: [Qemu-devel] AArch64: ZCR and ARM_CP_SVE/ARM_CP_FPU flags
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To: Richard Henderson <richard.henderson@linaro.org>, Peter Maydell <peter.maydell@linaro.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Hi,

ZCR system registers are both flagged as ARM_CP_SVE and ARM_CP_FPU,
which results in an assertion failure in fp_access_check due to the
check of these flags in handle_sys:

    if ((ri->type & ARM_CP_SVE) && !sve_access_check(s)) {
        return;
    }
    if ((ri->type & ARM_CP_FPU) && !fp_access_check(s)) {
        return;
    }

sve_access_check calls fp_access_check so the assert
!s->fp_access_checked in the second call to fp_access_check will fail.

I took a quick look at sve_exception_el and given that it checks that
FPU is enabled, can't we just remove the ARM_CP_FPU flag from ZCR?

Alternatively the second call to fp_access_check when ARM_CP_FPU is
defined could be skipped if ARM_CP_SVE is set.

Thanks,

Laurent