Messages in this thread | | | Date | Tue, 02 Apr 2024 14:43:06 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH] irqchip/gic-v3-its: Don't need VSYNC if VMAPP with {V, Alloc}=={0, x} |
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On Tue, 02 Apr 2024 14:32:40 +0100, Tangnianyao <tangnianyao@huawei.com> wrote: > > > > On 4/2/2024 20:35, Marc Zyngier wrote: > > On Tue, 02 Apr 2024 12:41:47 +0100, > > t00849498 <tangnianyao@huawei.com> wrote: > >> From GIC spec, a VMAPP with {V, Alloc}=={0, x} is self-synchronizing, > > It'd be nice to quote the part of the spec (5.3.19). > yes, that's quote from GIC spec. > >> This means the ITS command queue does not show the command as > >> consumed until all of its effects are completed. A VSYNC with unmapped > >> vpeid is not needed. > >> > >> Signed-off-by: t00849498 <tangnianyao@huawei.com> > > Previous contributions with the same email address had the name > > "Nianyao Tang" associated with it. Was it wrong in the past? Or is the > > above wrong? > Sorry, the above name is wrong, should be "Nianyao Tang". > > > >> --- > >> drivers/irqchip/irq-gic-v3-its.c | 4 ++++ > >> 1 file changed, 4 insertions(+) > >> > >> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > >> index fca888b36680..a0ca5dcbb245 100644 > >> --- a/drivers/irqchip/irq-gic-v3-its.c > >> +++ b/drivers/irqchip/irq-gic-v3-its.c > >> @@ -789,6 +789,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its, > >> unsigned long vpt_addr, vconf_addr; > >> u64 target; > >> bool alloc; > >> + bool unmap_v4_1 = !desc->its_vmapp_cmd.valid && is_v4_1(its); > >> > >> its_encode_cmd(cmd, GITS_CMD_VMAPP); > >> its_encode_vpeid(cmd, desc->its_vmapp_cmd.vpe->vpe_id); > >> @@ -832,6 +833,9 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its, > >> out: > >> its_fixup_cmd(cmd); > >> > >> + if (unmap_v4_1) > >> + return NULL; > >> + > >> return valid_vpe(its, desc->its_vmapp_cmd.vpe); > >> } > >> > > This is a bit ugly. We already have a whole block dedicated to > > handling VMAPP with V=0 and GICv4.1, and it'd be more readable to keep > > all that code together. Something like the untested patch below. > > Thank you for quick fix, it would be great to remove this VSYNC. ITS handling VSYNC unmap > vpeid may waste some time, trigger exception and needed to be > handled.
Do you actually see an exception being delivered from this?
In any case, feel free to respin the patch after having tested this diff, with the commit message fixed and a Fixes: tag attached to it.
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
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