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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2022 08:32:27.6045 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ee3b017a-d0c7-43bc-82ae-08d9da5d0f7b X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT058.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR08MB5165 Hi, > On 17 Jan 2022, at 14:15, Julien Grall wrote: >=20 > Hi, >=20 > 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. >=20 >=20 > Technically, the current form of CONFIG_QEMU allows the same binary to bo= ot on QEMU with GICv2 or GICv3. >=20 >> If we want to use GICv3, >> we can select the QEMU_LEGACY configuration. >=20 > AFAIK, GICv3 is not a legacy feature... So it feels a bit odd to name it = like that (see more below). >=20 >> Signed-off-by: Dongjiu Geng >> --- >> 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/Kco= nfig >> 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 >=3D v3.1.0" >=20 > This is a bit misleading. A user may select this thinking that this will = select GICv3. However, this will not. >=20 > 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, th= en I am afraid that this patch would be a no-go for me. >=20 > Looking at overall discussion, you seem to push the patch only to allow b= uilding a tiny Xen for QEMU and the new vGIC. >=20 > 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 t= hat if you want to try it then you have to use the default configuration. >=20 > @Dongjiu, is there any reason why you want to use the tiny QEMU config ra= ther than the default configuration? >=20 > @Bertrand, @Stefano, what do you think? I do think that the new Legacy option is very misleading and users will ten= d to select Qemu instead of the legacy one where having GICv3 makes more se= nse. Using the new VGIC which is unsupported is not a standard use case so maybe= it would make more sense to create a specific Qemu entry for GICv2 using n= ew VGIC instead and keep the default as is. To sum up I am no in favour of a solution changing the existing QEMU. A sol= ution creating a new one for the wanted use case would be better for me. Cheers Bertrand >=20 > Cheers, >=20 > --=20 > Julien Grall