Messages in this thread | | | Subject | Re: [PATCH v5 16/23] irqchip/gic-v4.1: Eagerly vmap vPEs | From | Zenghui Yu <> | Date | Fri, 20 Mar 2020 10:31:20 +0800 |
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Hi Marc,
On 2020/3/19 18:55, Marc Zyngier wrote: > On 2020-03-17 02:49, Zenghui Yu wrote: >> Hi Marc, >> >> On 2020/3/5 4:33, Marc Zyngier wrote: >>> Now that we have HW-accelerated SGIs being delivered to VPEs, it >>> becomes required to map the VPEs on all ITSs instead of relying >>> on the lazy approach that we would use when using the ITS-list >>> mechanism. >>> >>> Signed-off-by: Marc Zyngier <maz@kernel.org> >> >> Before GICv4.1, we use vlpi_count to evaluate whether the vPE has been >> mapped on the specified ITS, and use this refcount to only issue VMOVP >> to those involved ITSes. It's broken after this patch. >> >> We may need to re-evaluate "whether the vPE is mapped" now that we're at >> GICv4.1, otherwise *no* VMOVP will be issued on the v4.1 capable machine >> (I mean those without single VMOVP support). >> >> What I'm saying is something like below (only an idea, it even can't >> compile), any thoughts? >> >> >> diff --git a/drivers/irqchip/irq-gic-v3-its.c >> b/drivers/irqchip/irq-gic-v3-its.c >> index 2e12bc52e3a2..3450b5e847ca 100644 >> --- a/drivers/irqchip/irq-gic-v3-its.c >> +++ b/drivers/irqchip/irq-gic-v3-its.c >> @@ -198,7 +198,8 @@ static u16 get_its_list(struct its_vm *vm) >> if (!is_v4(its)) >> continue; >> >> - if (vm->vlpi_count[its->list_nr]) >> + if (vm->vlpi_count[its->list_nr] || >> + gic_requires_eager_mapping()) >> __set_bit(its->list_nr, &its_list); >> } >> >> @@ -1295,7 +1296,8 @@ static void its_send_vmovp(struct its_vpe *vpe) >> if (!is_v4(its)) >> continue; >> >> - if (!vpe->its_vm->vlpi_count[its->list_nr]) >> + if (!vpe->its_vm->vlpi_count[its->list_nr] && >> + !gic_requires_eager_mapping()) >> continue; >> >> desc.its_vmovp_cmd.col = &its->collections[col_id]; > > It took me a while to wrap my head around that one, but you're as usual > spot on. > > The use of gic_requires_eager_mapping() is a bit confusing here, as it > isn't > so much that the VPE is eagerly mapped, but the predicate on which we > evaluate > the need for a VMOVP. How about this: > > diff --git a/drivers/irqchip/irq-gic-v3-its.c > b/drivers/irqchip/irq-gic-v3-its.c > index cd6451e190c9..348f7a909a69 100644 > --- a/drivers/irqchip/irq-gic-v3-its.c > +++ b/drivers/irqchip/irq-gic-v3-its.c > @@ -189,6 +189,15 @@ static DEFINE_IDA(its_vpeid_ida); > #define gic_data_rdist_rd_base() (gic_data_rdist()->rd_base) > #define gic_data_rdist_vlpi_base() (gic_data_rdist_rd_base() + > SZ_128K) > > +/* > + * Skip ITSs that have no vLPIs mapped, unless we're on GICv4.1, as we > + * always have vSGIs mapped. > + */ > +static bool require_its_list_vmovp(struct its_vm *vm, struct its_node > *its) > +{ > + return (gic_rdists->has_rvpeid || vm->vlpi_count[its->list_nr]); > +} > + > static u16 get_its_list(struct its_vm *vm) > { > struct its_node *its; > @@ -198,7 +207,7 @@ static u16 get_its_list(struct its_vm *vm) > if (!is_v4(its)) > continue; > > - if (vm->vlpi_count[its->list_nr]) > + if (require_its_list_vmovp(vm, its)) > __set_bit(its->list_nr, &its_list); > } > > @@ -1295,7 +1304,7 @@ static void its_send_vmovp(struct its_vpe *vpe) > if (!is_v4(its)) > continue; > > - if (!vpe->its_vm->vlpi_count[its->list_nr]) > + if (!require_its_list_vmovp(vpe->its_vm, its)) > continue; > > desc.its_vmovp_cmd.col = &its->collections[col_id];
Indeed this looks much clearer. We're actually evaluating the need for issuing VMOVP to a specified ITS, on system using its_list_map feature (though we evaluate it by checking whether the vPE is mapped on this ITS).
Thanks, Zenghui
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