Re: [PATCH v5 19/22] hvm/params: Add a new delivery type for event-channel in HVM_PARAM_CALLBACK_IRQ

From: "Jan Beulich" <JBeulich@suse.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: hangaohuai@huawei.com, xen-devel@lists.xen.org,
	stefano.stabellini@citrix.com, shannon.zhao@linaro.org,
	Shannon Zhao <zhaoshenglong@huawei.com>
Subject: Re: [PATCH v5 19/22] hvm/params: Add a new delivery type for event-channel in HVM_PARAM_CALLBACK_IRQ
Date: Fri, 04 Mar 2016 05:20:39 -0700	[thread overview]
Message-ID: <56D98BA702000078000D9610@prv-mh.provo.novell.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1603041202010.17938@kaball.uk.xensource.com>

>>> On 04.03.16 at 13:09, <stefano.stabellini@eu.citrix.com> wrote:
> On Fri, 4 Mar 2016, Jan Beulich wrote:
>> >>> On 04.03.16 at 07:15, <zhaoshenglong@huawei.com> wrote:
>> > From: Shannon Zhao <shannon.zhao@linaro.org>
>> > 
>> > Add a new delivery type:
>> > val[63:56] == 3: val[15:8] is flag: val[7:0] is a PPI.
>> > To the flag, bit 8 stands the interrupt mode is edge(1) or level(0) and
>> > bit 9 stands the interrupt polarity is active low(1) or high(0).
>> > 
>> > Cc: Jan Beulich <jbeulich@suse.com>
>> > Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
>> 
>> The set of Cc-s is too narrow - all REST maintainers should be copied.
>> 
>> > --- a/xen/include/public/hvm/params.h
>> > +++ b/xen/include/public/hvm/params.h
>> > @@ -55,6 +55,16 @@
>> >   * if this delivery method is available.
>> >   */
>> >  
>> > +#define HVM_PARAM_CALLBACK_TYPE_EVENT    3
>> > +/*
>> > + * val[55:16] need to be zero.
>> > + * val[15:8] is flag of event-channel interrupt:
>> > + *  bit 8: interrupt is edge(1) or level(0) triggered
>> > + *  bit 9: interrupt is active low(1) or high(0)
>> > + * val[7:0] is PPI number used by event-channel.
>> > + * This is only used by ARM/ARM64.
>> > + */
>> 
>> I think the name of the constant needs improvement. The low 8
>> bits make this extremely ARM specific, so perhaps
>> HVM_PARAM_CALLBACK_TYPE_PPI?
> 
> That would be OK for me.
> 
> 
>> Albeit - wouldn't the
>> vector and/or GSI ones be re-usable for this purpose? (I
>> don't know enough about ARM to be certain.)
> 
> Vector is an x86 thing, while GSI is an ACPI term. There is probably a
> PPI to GSI mapping on ARM ACPI systems, but I wouldn't want this
> HVM_PARAM to work only with ACPI: it should work with device tree
> systems too, where GSI has no meaning.

Okay. Then how about making _VECTOR x86-specific, and the
new one ARM-specific (via #ifdef), at once allowing (if so
wanted) both to share the same numeric value?

Jan

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