Re: [Qemu-devel] [PATCH] target-s390x: Implement stfl and stfle

From: Richard Henderson <rth@twiddle.net>
To: Michal Marek <mmarek@suse.com>, Alexander Graf <agraf@suse.de>
Cc: qemu-devel@nongnu.org, Miroslav Benes <mbenes@suse.cz>,
	Eric Bischoff <ebischoff@suse.com>
Subject: Re: [Qemu-devel] [PATCH] target-s390x: Implement stfl and stfle
Date: Sat, 25 Feb 2017 11:05:55 +1100	[thread overview]
Message-ID: <a634716c-c998-c422-6802-946a283f8837@twiddle.net> (raw)
In-Reply-To: <20170224134411.28882-1-mmarek@suse.com>

On 02/25/2017 12:44 AM, Michal Marek wrote:
> +DEF_HELPER_1(stfl, void, env)

DEF_HELPER_FLAGS_1(stfl, TCG_CALL_NO_RWG, void, env)

since this touches no registers, and only writes to lomem which afaik cannot 
fault in kernel mode.

> +DEF_HELPER_3(stfle, i64, env, i64, i64)

Unfortunately, we are writing to cc_op, so we do have a TCG register write, so 
I guess this is the best we can do here.

> +static int do_stfle(CPUS390XState *env, uint64_t addr, int len)
> +{
> +    S390CPU *cpu = s390_env_get_cpu(env);
> +    uint8_t data[64];

S390FeatBitmap or S390FeatInit?  Or even a sizeof?
Hard coding 64 certainly doesn't seem right.

> +    memset(data, 0, sizeof(data));
> +    res = s390_fill_feat_block(cpu->model->features, S390_FEAT_TYPE_STFL, data);
> +    cpu_physical_memory_write(addr, data, MIN(res, len));

No, not physical memory, you need to write to virtual memory, at least for 
STFLE.  Which, as you'll recall can be used from user-mode.

r~