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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v4] xen/arm: Allow QEMU platform to be built with GICv2
Hi Dongju, > On 18 Jan 2022, at 08:58, Dongjiu Geng <gengdongjiu1@xxxxxxxxx> wrote: > > Bertrand Marquis <Bertrand.Marquis@xxxxxxx> 于2022年1月18日周二 16:48写道： >> >> Hi Dongju, >> >>> On 18 Jan 2022, at 08:45, Dongjiu Geng <gengdongjiu1@xxxxxxxxx> wrote: >>> >>> Julien Grall <julien@xxxxxxx> 于2022年1月17日周一 22:16写道： >>>> >>>> Hi, >>>> >>>> On 17/01/2022 10:40, Dongjiu Geng wrote: >>>>> It turns out that QEMU has been supporting GICv2 virtualization since >>>>> v3.1.0. So remove the dependencies on GICv3. >>>> >>>> >>>> Technically, the current form of CONFIG_QEMU allows the same binary to >>>> boot on QEMU with GICv2 or GICv3. >>>> >>>>> If we want to use GICv3, >>>>> we can select the QEMU_LEGACY configuration. >>>> >>>> AFAIK, GICv3 is not a legacy feature... So it feels a bit odd to name it >>>> like that (see more below). >>> >>> Legacy means QEMU platform only supports GICV3, now it can support >>> both GICv2 and GICv3. The scope of support has been expanded >>> Not mean GICv3 is a legacy feature. >> >> You might be misleading a bit here. >> In the current configuration, Xen support GICv2, GICv3 and vgic. >> The only thing not supported is actually the new VGIC but this is an >> unsupported feature not fully functional which shall be used with caution. >> >> What issue exactly do you have in Qemu configured for gicv2 when you use the >> default configuration ? > > I want to use NEW_VGIC with GICv2, but QEMU only select GICV3, when > GICv3 is select, the NEW_VGIC can not be used. I try the NEW_VGIC > with GICv2, not found issue. so I want to remove this limitation. > If you think we should not support NEW_VGIC feature, we can ignore > this patch. thanks! Supporting GICv2 makes sense but using NEW_VGIC in Xen might not as it is not security supported and does not support ITS and MSIs. Do you have a reason to use the NEW_VGIC implementation instead of the standard one ? Cheers Bertrand > >> >> Cheers >> Bertrand >> >>> >>>> >>>>> >>>>> Signed-off-by: Dongjiu Geng <gengdongjiu1@xxxxxxxxx> >>>>> --- >>>>> xen/arch/arm/platforms/Kconfig | 10 +++++++++- >>>>> 1 file changed, 9 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/xen/arch/arm/platforms/Kconfig >>>>> b/xen/arch/arm/platforms/Kconfig >>>>> index c93a6b2756..41e82a42ee 100644 >>>>> --- a/xen/arch/arm/platforms/Kconfig >>>>> +++ b/xen/arch/arm/platforms/Kconfig >>>>> @@ -13,7 +13,15 @@ config ALL_PLAT >>>>> automatically select any of the related drivers. >>>>> >>>>> config QEMU >>>>> - bool "QEMU aarch virt machine support" >>>>> + bool "QEMU aarch virt machine support >= v3.1.0" >>>> >>>> This is a bit misleading. A user may select this thinking that this will >>>> select GICv3. However, this will not. >>>> >>>> This also raises the question of what is the default GIC version in QEMU >>>> (i.e. if you don't pass anything on the command line)? If this is GICv3, >>>> then I am afraid that this patch would be a no-go for me. >>>> >>>> Looking at overall discussion, you seem to push the patch only to allow >>>> building a tiny Xen for QEMU and the new vGIC. >>>> >>>> The default Xen (i.e. make defconfig) will also work on QEMU. Given that >>>> the new vGIC is a still in development, I am seriously considering to >>>> say that if you want to try it then you have to use the default >>>> configuration. >>>> >>>> @Dongjiu, is there any reason why you want to use the tiny QEMU config >>>> rather than the default configuration? >>> >>> Hi Julien, thanks for the reply, I do not use the tiny QEMU config. I >>> used the default configuration and selected the platform as QEMU. >>> But QEMU platform only slects GICV3, so I submit this patch to remove >>> the limitation because I want to use VGIC. VGIC can already support >>> GICv2 now. >>> >>>> >>>> @Bertrand, @Stefano, what do you think? >>>> >>>> Cheers, >>>> >>>> -- >>>> Julien Grall
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