Messages in this thread Patch in this message | | | Date | Tue, 02 Apr 2024 13:35:35 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH] irqchip/gic-v3-its: Don't need VSYNC if VMAPP with {V, Alloc}=={0, x} |
| |
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).
> 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?
> --- > 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.
Thanks,
M.
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index fca888b36680..2a537cbfcb07 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -786,6 +786,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its, struct its_cmd_block *cmd, struct its_cmd_desc *desc) { + struct its_vpe *vpe = valid_vpe(its, desc->its_vmapp_cmd.vpe); unsigned long vpt_addr, vconf_addr; u64 target; bool alloc; @@ -798,6 +799,11 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its, if (is_v4_1(its)) { alloc = !atomic_dec_return(&desc->its_vmapp_cmd.vpe->vmapp_count); its_encode_alloc(cmd, alloc); + /* + * Unmapping a VPE is self-synchronizing on GICv4.1, + * no need to issue a VSYNC. + */ + vpe = NULL; } goto out; @@ -832,7 +838,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its, out: its_fixup_cmd(cmd); - return valid_vpe(its, desc->its_vmapp_cmd.vpe); + return vpe; } static struct its_vpe *its_build_vmapti_cmd(struct its_node *its, -- Without deviation from the norm, progress is not possible.
| |