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acpidmar(4): Store PCI domain in softc for segment mapping
On Wed, Jul 29, 2026 at 11:12:52PM +0200, Mark Kettenis wrote:
> > Date: Tue, 28 Jul 2026 15:39:46 +0200
> > From: hshoexer <hshoexer@yerbouti.franken.de>
> >
> > Hi,
> >
> > with this change I store the PCI domain in the softc. Later I use
> > that value when mapping domain to segment. Instead of counting.
>
> The way acpipci(4) works we already have a 1:1 mapping between PCI
> segments and PCI domains. Technically that isn't necessarily correct,
> but in practice that seems to be the only workable approach.
>
> > Also fall back to segment 0, when ACPI did not provide a segment.
>
> If APCI doesn't provide a segment, we already set it to 0. This is
> required by the standard. So...
>
> > This actually enforces use of the IOMMU.
> >
> > While there:
> > - tweak printf to use segment instead of PCI domain
> > - use ACPI provided segment instead of hardcoded 0 in ivhd_showpage()
> >
> > ok?
> >
> > Take care,
> > HJ.
> >
> > -----------------------------------------------------------------------------
> > diff --git a/sys/arch/amd64/pci/acpipci.c b/sys/arch/amd64/pci/acpipci.c
> > index e3121987654..e5e861662d7 100644
> > --- a/sys/arch/amd64/pci/acpipci.c
> > +++ b/sys/arch/amd64/pci/acpipci.c
> > @@ -66,6 +66,7 @@ struct acpipci_softc {
> > char sc_memex_name[32];
> > int sc_bus;
> > uint32_t sc_seg;
> > + int sc_domain;
> > };
> >
> > int acpipci_match(struct device *, void *, void *);
> > @@ -97,15 +98,14 @@ int
> > acpipci_domain_to_seg(int domain)
> > {
> > struct acpipci_softc *sc;
> > - int i, d = 0;
> > + int i;
> >
> > for (i = 0; i < acpipci_cd.cd_ndevs; i++) {
> > sc = (struct acpipci_softc *)acpipci_cd.cd_devs[i];
> > if (sc == NULL)
> > continue;
> > - if (d == domain)
> > + if (sc->sc_domain == domain)
> > return sc->sc_seg;
> > - d++;
> > }
> >
> > return -1;
> > @@ -147,6 +147,9 @@ acpipci_attach(struct device *parent, struct device *self, void *aux)
> > aml_evalinteger(sc->sc_acpi, sc->sc_node, "_SEG", 0, NULL, &seg);
> > sc->sc_seg = seg;
> >
> > + /* Assigned when the PCI bus attaches. */
> > + sc->sc_domain = -1;
> > +
> > if (aml_evalname(sc->sc_acpi, sc->sc_node, "_CRS", 0, NULL, &res)) {
> > printf(": can't find resources\n");
> >
> > @@ -210,6 +213,7 @@ acpipci_attach_bus(struct device *parent, struct acpipci_softc *sc)
> > pba.pba_pmemex = sc->sc_memex;
> > pba.pba_domain = pci_ndomains++;
> > pba.pba_bus = sc->sc_bus;
> > + sc->sc_domain = pba.pba_domain;
> >
> > /* Enable MSI in ACPI 2.0 and above, unless we're told not to. */
> > if (sc->sc_acpi->sc_fadt->hdr.revision >= 2 &&
> > diff --git a/sys/dev/acpi/acpidmar.c b/sys/dev/acpi/acpidmar.c
> > index 57b90ddb193..cf18265fd09 100644
> > --- a/sys/dev/acpi/acpidmar.c
> > +++ b/sys/dev/acpi/acpidmar.c
> > @@ -2581,9 +2581,8 @@ acpidmar_pci_hook(pci_chipset_tag_t pc, struct pci_attach_args *pa)
> >
> > segment = acpipci_domain_to_seg(pa->pa_domain);
> > if (segment < 0) {
> > - DPRINTF(1, "acpidmar: no ACPI segment for pci domain %d\n",
> > - pa->pa_domain);
> > - return;
> > + /* Fall back to segment 0. */
> > + segment = 0;
> > }
>
> So it we ever get a -1 here, somethings is really wrong. So I'd
> probably turn this into:
>
> KASSERT(segment >= 0);
good point! Uupdated diff below.
ok?
>
> Otherwise this looks good.
>
> I'm still curious to see any x86 AML that actually uses non-zero _SEG
> numbers.
>
> > /* Record PCI-PCI bridge forwarding windows */
> > @@ -2608,7 +2607,7 @@ acpidmar_pci_hook(pci_chipset_tag_t pc, struct pci_attach_args *pa)
> > PCI_SUBCLASS(reg) == PCI_SUBCLASS_BRIDGE_ISA) {
> > /* For ISA Bridges, map 0-16Mb as 1:1 */
> > printf("dmar: %.4x:%.2x:%.2x.%x mapping ISA\n",
> > - pa->pa_domain, bus, dev, fun);
> > + segment, bus, dev, fun);
> > domain_map_pthru(dom, 0x00, 16*1024*1024);
> >
> > /* Keep the identity mapped IOVA range out of the allocator */
> > @@ -2917,7 +2916,7 @@ ivhd_showpage(struct iommu_softc *iommu, int sid, paddr_t paddr)
> > if (show > 10)
> > return;
> > show++;
> > - dom = acpidmar_pci_attach(acpidmar_sc, 0, sid, 0);
> > + dom = acpidmar_pci_attach(acpidmar_sc, iommu->segment, sid, 0);
> > if (!dom)
> > return;
> > printf("DTE: %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
> >
> >
------------
acpidmar(4): Store PCI domain in softc for segment mapping
Ensure we get a valid segement and enforce use of the IOMMU.
While there:
- tweak printf to use segment instead of PCI domain
- use ACPI provided segment instead of hardcoded 0 in ivhd_showpage()
---
sys/arch/amd64/pci/acpipci.c | 10 +++++++---
sys/dev/acpi/acpidmar.c | 10 +++-------
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/sys/arch/amd64/pci/acpipci.c b/sys/arch/amd64/pci/acpipci.c
index e3121987654..e5e861662d7 100644
--- a/sys/arch/amd64/pci/acpipci.c
+++ b/sys/arch/amd64/pci/acpipci.c
@@ -66,6 +66,7 @@ struct acpipci_softc {
char sc_memex_name[32];
int sc_bus;
uint32_t sc_seg;
+ int sc_domain;
};
int acpipci_match(struct device *, void *, void *);
@@ -97,15 +98,14 @@ int
acpipci_domain_to_seg(int domain)
{
struct acpipci_softc *sc;
- int i, d = 0;
+ int i;
for (i = 0; i < acpipci_cd.cd_ndevs; i++) {
sc = (struct acpipci_softc *)acpipci_cd.cd_devs[i];
if (sc == NULL)
continue;
- if (d == domain)
+ if (sc->sc_domain == domain)
return sc->sc_seg;
- d++;
}
return -1;
@@ -147,6 +147,9 @@ acpipci_attach(struct device *parent, struct device *self, void *aux)
aml_evalinteger(sc->sc_acpi, sc->sc_node, "_SEG", 0, NULL, &seg);
sc->sc_seg = seg;
+ /* Assigned when the PCI bus attaches. */
+ sc->sc_domain = -1;
+
if (aml_evalname(sc->sc_acpi, sc->sc_node, "_CRS", 0, NULL, &res)) {
printf(": can't find resources\n");
@@ -210,6 +213,7 @@ acpipci_attach_bus(struct device *parent, struct acpipci_softc *sc)
pba.pba_pmemex = sc->sc_memex;
pba.pba_domain = pci_ndomains++;
pba.pba_bus = sc->sc_bus;
+ sc->sc_domain = pba.pba_domain;
/* Enable MSI in ACPI 2.0 and above, unless we're told not to. */
if (sc->sc_acpi->sc_fadt->hdr.revision >= 2 &&
diff --git a/sys/dev/acpi/acpidmar.c b/sys/dev/acpi/acpidmar.c
index 5771a54ffc9..57581f0e48a 100644
--- a/sys/dev/acpi/acpidmar.c
+++ b/sys/dev/acpi/acpidmar.c
@@ -2556,11 +2556,7 @@ acpidmar_pci_hook(pci_chipset_tag_t pc, struct pci_attach_args *pa)
reg = pci_conf_read(pc, pa->pa_tag, PCI_CLASS_REG);
segment = acpipci_domain_to_seg(pa->pa_domain);
- if (segment < 0) {
- DPRINTF(1, "acpidmar: no ACPI segment for pci domain %d\n",
- pa->pa_domain);
- return;
- }
+ KASSERT(segment >= 0);
/* Record PCI-PCI bridge forwarding windows */
bhlc = pci_conf_read(pc, pa->pa_tag, PCI_BHLC_REG);
@@ -2584,7 +2580,7 @@ acpidmar_pci_hook(pci_chipset_tag_t pc, struct pci_attach_args *pa)
PCI_SUBCLASS(reg) == PCI_SUBCLASS_BRIDGE_ISA) {
/* For ISA Bridges, map 0-16Mb as 1:1 */
printf("dmar: %.4x:%.2x:%.2x.%x mapping ISA\n",
- pa->pa_domain, bus, dev, fun);
+ segment, bus, dev, fun);
domain_map_pthru(dom, 0x00, 16*1024*1024);
/* Keep the identity mapped IOVA range out of the allocator */
@@ -2893,7 +2889,7 @@ ivhd_showpage(struct iommu_softc *iommu, int sid, paddr_t paddr)
if (show > 10)
return;
show++;
- dom = acpidmar_pci_attach(acpidmar_sc, 0, sid, 0);
+ dom = acpidmar_pci_attach(acpidmar_sc, iommu->segment, sid, 0);
if (!dom)
return;
printf("DTE: %.8x %.8x %.8x %.8x %.8x %.8x %.8x %.8x\n",
--
2.55.0
acpidmar(4): Store PCI domain in softc for segment mapping