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Date: Fri, 27 Sep 2019 10:01:40 +0800 From: Zenghui Yu <yuzenghui@...wei.com> To: Marc Zyngier <maz@...nel.org>, <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org> CC: Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Jason Cooper <jason@...edaemon.net>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH 10/35] irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER) allocation On 2019/9/27 0:27, Marc Zyngier wrote: > On 26/09/2019 16:57, Marc Zyngier wrote: >> On 26/09/2019 16:19, Zenghui Yu wrote: >>> Hi Marc, >>> >>> Two more questions below. >>> >>> On 2019/9/25 22:41, Marc Zyngier wrote: >>>> On 25/09/2019 14:04, Zenghui Yu wrote: >>>>> Hi Marc, >>>>> >>>>> Some questions about this patch, mostly to confirm that I would >>>>> understand things here correctly. >>>>> >>>>> On 2019/9/24 2:25, Marc Zyngier wrote: >>>>>> GICv4.1 defines a new VPE table that is potentially shared between >>>>>> both the ITSs and the redistributors, following complicated affinity >>>>>> rules. >>>>>> >>>>>> To make things more confusing, the programming of this table at >>>>>> the redistributor level is reusing the GICv4.0 GICR_VPROPBASER register >>>>>> for something completely different. >>>>>> >>>>>> The code flow is somewhat complexified by the need to respect the >>>>>> affinities required by the HW, meaning that tables can either be >>>>>> inherited from a previously discovered ITS or redistributor. >>>>>> >>>>>> Signed-off-by: Marc Zyngier <maz@...nel.org> >>>>>> --- >>>>> >>>>> [...] >>>>> >>>>>> @@ -1962,6 +1965,65 @@ static bool its_parse_indirect_baser(struct its_node *its, >>>>>> return indirect; >>>>>> } >>>>>> >>>>>> +static u32 compute_common_aff(u64 val) >>>>>> +{ >>>>>> + u32 aff, clpiaff; >>>>>> + >>>>>> + aff = FIELD_GET(GICR_TYPER_AFFINITY, val); >>>>>> + clpiaff = FIELD_GET(GICR_TYPER_COMMON_LPI_AFF, val); >>>>>> + >>>>>> + return aff & ~(GENMASK(31, 0) >> (clpiaff * 8)); >>>>>> +} >>>>>> + >>>>>> +static u32 compute_its_aff(struct its_node *its) >>>>>> +{ >>>>>> + u64 val; >>>>>> + u32 svpet; >>>>>> + >>>>>> + /* >>>>>> + * Reencode the ITS SVPET and MPIDR as a GICR_TYPER, and compute >>>>>> + * the resulting affinity. We then use that to see if this match >>>>>> + * our own affinity. >>>>>> + */ >>>>>> + svpet = FIELD_GET(GITS_TYPER_SVPET, its->typer); >>> >>> The spec says, ITS does not share vPE table with Redistributors when >>> SVPET==0. It seems that we miss this rule and simply regard SVPET as >>> GICR_TYPER_COMMON_LPI_AFF here. Am I wrong? >> >> Correct. I missed the case where the ITS doesn't share anything. That's >> pretty unlikely though (you loose all the benefit of v4.1, and I don't >> really see how you'd make it work reliably). > > Actually, this is already handled... > >> >>> >>>>>> + val = FIELD_PREP(GICR_TYPER_COMMON_LPI_AFF, svpet); >>>>>> + val |= FIELD_PREP(GICR_TYPER_AFFINITY, its->mpidr); >>>>>> + return compute_common_aff(val); >>>>>> +} >>>>>> + >>>>>> +static struct its_node *find_sibbling_its(struct its_node *cur_its) >>>>>> +{ >>>>>> + struct its_node *its; >>>>>> + u32 aff; >>>>>> + >>>>>> + if (!FIELD_GET(GITS_TYPER_SVPET, cur_its->typer)) >>>>>> + return NULL; > > ... here. If SVPET is 0, there is no sibling, and we'll allocate a VPE > table as usual. Yes, I see. So we can safely encode the non-zero SVPET as COMMON_LPI_AFF in a GICR_TYPER when computing the affinity. Thanks, zenghui
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