From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Michael Kelley <mikelley@microsoft.com>,
Chen Zhou <chenzhou10@huawei.com>
Cc: "linux-hyperv\@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"chenzhou10\@huawei.com" <chenzhou10@huawei.com>,
"tglx\@linutronix.de" <tglx@linutronix.de>,
"mingo\@redhat.com" <mingo@redhat.com>
Subject: RE: [PATCH] x86/hyper-v: remove unnecessary conversions to bool
Date: Mon, 13 Jan 2020 09:07:45 +0100 [thread overview]
Message-ID: <87tv4zpyni.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <MW2PR2101MB1052B01B542F0C0A576928CBD73A0@MW2PR2101MB1052.namprd21.prod.outlook.com>
Michael Kelley <mikelley@microsoft.com> writes:
> From: Vitaly Kuznetsov <vkuznets@redhat.com> Sent: Friday, January 10, 2020 4:00 AM
>>
>>
>> I'd suggest we get rid of bool functions completely instead, something
>> like (untested):
>
> Just curious: Why prefer returning a u16 instead of a bool? To avoid
> having to test 'ret' for zero in the return statements, or is there some
> broader reason?
Basically to preserve hypercall failure code and not hide it under 'false'.
>> - ipi_arg.cpu_mask);
>> - return ((ret == 0) ? true : false);
>> + return (u16)hv_do_fast_hypercall16(HVCALL_SEND_IPI, ipi_arg.vector,
>> + ipi_arg.cpu_mask);
>
> The cast to u16 seems a bit dangerous. The hypercall status code is indeed
> returned in the low 16 bits of the hypercall result value, so it works, and
> maybe that is why you suggested u16 as the function return value. But it
> is a non-obvious assumption.
This is not obvious, I agree, and we can create a wrapper for it but we
more or less must convert it to 'u16': uppper bits don't indicate a
failure (e.g. 'reps complete').
--
Vitaly
prev parent reply other threads:[~2020-01-13 8:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 7:20 [PATCH] x86/hyper-v: remove unnecessary conversions to bool Chen Zhou
2020-01-10 11:59 ` Vitaly Kuznetsov
2020-01-12 16:43 ` Michael Kelley
2020-01-13 8:07 ` Vitaly Kuznetsov [this message]
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