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mbuf dma 64 bit
On Fri, Feb 13, 2026 at 11:37:27AM +0100, Mark Kettenis wrote:
> Getting the driver bits in will help the bounce buffers. And I don't
> think the rest of this diff should be considered before we have bounce
> buffers.
Driver bits are in. The idea of my diff is to mark network drivers
that can do 64 bit mbufs. If all interfaces during attach have
this feature, we allocate mbufs in high memory.
Problematic are hotplug PCI, CardBus and Thunderbolt busses which
attach devices that do not support 64 bit DMA. Machines running
i386 or with less than 2 GB RAM are not affected. USB ethernet or
USB wifi hotplug is not affected.
What options do we have to get this in?
1. Ignore these machines, devices won't work.
2. Detect the problem during ifconfig up and print an error.
Maybe it works after a reboot if the device is attached during boot.
3. Wait for mbuf bounce buffer diff for unsupported devices.
4. Wait until someone implements IOMMU. But this is not
available for all machines.
Question is how relevant are problematic setups for our user base.
Can we risk to do 1 or 2?
Is the mbuf bounce buffer implementation nearly finished and we can
commit it and do 3?
bluhm
Index: arch/amd64/amd64/autoconf.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/arch/amd64/amd64/autoconf.c,v
diff -u -p -r1.59 autoconf.c
--- arch/amd64/amd64/autoconf.c 12 Nov 2025 10:00:27 -0000 1.59
+++ arch/amd64/amd64/autoconf.c 4 Mar 2026 14:50:42 -0000
@@ -108,6 +108,23 @@ unmap_startup(void)
} while (p < (vaddr_t)endboot);
}
+void
+mbuf_dma_64bit_enable(void)
+{
+ struct ifnet *ifp;
+
+ TAILQ_FOREACH(ifp, &ifnetlist, if_list) {
+ if (!ISSET(ifp->if_xflags, IFXF_MBUF_64BIT)) {
+ printf("%s: restrict all mbufs to low memory\n",
+ ifp->if_xname);
+ return;
+ }
+ }
+
+ printf("enable mbufs in high memory\n");
+ m_pool_noconstraints();
+}
+
/*
* Determine i/o configuration for a machine.
*/
@@ -123,6 +140,8 @@ cpu_configure(void)
panic("configure: mainbus not configured");
intr_printconfig();
+
+ mbuf_dma_64bit_enable();
#if NIOAPIC > 0
lapic_set_lvt();
Index: dev/pci/if_bnxt.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_bnxt.c,v
diff -u -p -r1.67 if_bnxt.c
--- dev/pci/if_bnxt.c 19 Feb 2026 10:15:36 -0000 1.67
+++ dev/pci/if_bnxt.c 4 Mar 2026 14:47:53 -0000
@@ -654,7 +654,7 @@ bnxt_attach(struct device *parent, struc
strlcpy(ifp->if_xname, DEVNAME(sc), IFNAMSIZ);
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_MULTICAST | IFF_SIMPLEX;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = bnxt_ioctl;
ifp->if_qstart = bnxt_start;
ifp->if_watchdog = bnxt_watchdog;
Index: dev/pci/if_em.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_em.c,v
diff -u -p -r1.380 if_em.c
--- dev/pci/if_em.c 4 Mar 2026 14:15:36 -0000 1.380
+++ dev/pci/if_em.c 4 Mar 2026 14:47:53 -0000
@@ -1994,6 +1994,8 @@ em_setup_interface(struct em_softc *sc)
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
ifp->if_xflags = IFXF_MPSAFE;
+ if (ISSET(sc->sc_dmaflags, BUS_DMA_64BIT))
+ ifp->if_xflags |= IFXF_MBUF_64BIT;
ifp->if_ioctl = em_ioctl;
ifp->if_qstart = em_start;
ifp->if_watchdog = em_watchdog;
Index: dev/pci/if_ice.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ice.c,v
diff -u -p -r1.68 if_ice.c
--- dev/pci/if_ice.c 24 Feb 2026 20:14:29 -0000 1.68
+++ dev/pci/if_ice.c 4 Mar 2026 14:47:53 -0000
@@ -30657,7 +30657,7 @@ ice_attach_hook(struct device *self)
ifp->if_softc = sc;
strlcpy(ifp->if_xname, sc->sc_dev.dv_xname, IFNAMSIZ);
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = ice_ioctl;
ifp->if_qstart = ice_start;
ifp->if_watchdog = ice_watchdog;
Index: dev/pci/if_igc.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_igc.c,v
diff -u -p -r1.31 if_igc.c
--- dev/pci/if_igc.c 24 Feb 2026 23:01:10 -0000 1.31
+++ dev/pci/if_igc.c 4 Mar 2026 14:47:53 -0000
@@ -796,7 +796,7 @@ igc_setup_interface(struct igc_softc *sc
ifp->if_softc = sc;
strlcpy(ifp->if_xname, DEVNAME(sc), IFNAMSIZ);
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = igc_ioctl;
ifp->if_qstart = igc_start;
ifp->if_watchdog = igc_watchdog;
Index: dev/pci/if_ix.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ix.c,v
diff -u -p -r1.223 if_ix.c
--- dev/pci/if_ix.c 26 Feb 2026 23:38:10 -0000 1.223
+++ dev/pci/if_ix.c 4 Mar 2026 14:47:53 -0000
@@ -1929,7 +1929,7 @@ ixgbe_setup_interface(struct ix_softc *s
strlcpy(ifp->if_xname, sc->dev.dv_xname, IFNAMSIZ);
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = ixgbe_ioctl;
ifp->if_qstart = ixgbe_start;
ifp->if_timer = 0;
Index: dev/pci/if_ixl.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ixl.c,v
diff -u -p -r1.116 if_ixl.c
--- dev/pci/if_ixl.c 25 Feb 2026 23:40:49 -0000 1.116
+++ dev/pci/if_ixl.c 4 Mar 2026 14:47:53 -0000
@@ -1914,7 +1914,7 @@ ixl_attach(struct device *parent, struct
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = ixl_ioctl;
ifp->if_qstart = ixl_start;
ifp->if_watchdog = ixl_watchdog;
Index: dev/pci/if_ixv.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_ixv.c,v
diff -u -p -r1.2 if_ixv.c
--- dev/pci/if_ixv.c 14 Jul 2025 23:49:08 -0000 1.2
+++ dev/pci/if_ixv.c 4 Mar 2026 14:47:53 -0000
@@ -768,7 +768,7 @@ ixv_setup_interface(struct device *dev,
strlcpy(ifp->if_xname, sc->dev.dv_xname, IFNAMSIZ);
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = ixv_ioctl;
ifp->if_qstart = ixgbe_start;
ifp->if_timer = 0;
Index: dev/pci/if_mcx.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pci/if_mcx.c,v
diff -u -p -r1.121 if_mcx.c
--- dev/pci/if_mcx.c 19 Nov 2025 04:58:04 -0000 1.121
+++ dev/pci/if_mcx.c 4 Mar 2026 14:47:53 -0000
@@ -2953,7 +2953,7 @@ mcx_attach(struct device *parent, struct
strlcpy(ifp->if_xname, DEVNAME(sc), IFNAMSIZ);
ifp->if_softc = sc;
ifp->if_flags = IFF_BROADCAST | IFF_MULTICAST | IFF_SIMPLEX;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
ifp->if_ioctl = mcx_ioctl;
ifp->if_qstart = mcx_start;
ifp->if_watchdog = mcx_watchdog;
Index: dev/pv/if_vio.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/dev/pv/if_vio.c,v
diff -u -p -r1.78 if_vio.c
--- dev/pv/if_vio.c 15 Jan 2026 09:06:19 -0000 1.78
+++ dev/pv/if_vio.c 4 Mar 2026 14:47:53 -0000
@@ -750,7 +750,7 @@ negotiate:
ifp->if_capabilities = 0;
ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
- ifp->if_xflags = IFXF_MPSAFE;
+ ifp->if_xflags = IFXF_MPSAFE | IFXF_MBUF_64BIT;
#if NVLAN > 0
ifp->if_capabilities |= IFCAP_VLAN_MTU;
ifp->if_capabilities |= IFCAP_VLAN_HWOFFLOAD;
Index: kern/uipc_mbuf.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_mbuf.c,v
diff -u -p -r1.304 uipc_mbuf.c
--- kern/uipc_mbuf.c 5 Feb 2026 03:26:00 -0000 1.304
+++ kern/uipc_mbuf.c 4 Mar 2026 14:50:42 -0000
@@ -1480,6 +1480,17 @@ m_pool_init(struct pool *pp, u_int size,
pool_set_constraints(pp, &kp_dma_contig);
}
+void
+m_pool_noconstraints(void)
+{
+ int i;
+
+ pool_set_constraints(&mbpool, &kp_mbuf_contig);
+
+ for (i = 0; i < nitems(mclsizes); i++)
+ pool_set_constraints(&mclpools[i], &kp_mbuf_contig);
+}
+
u_int
m_pool_used(void)
{
Index: net/if.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/net/if.h,v
diff -u -p -r1.223 if.h
--- net/if.h 9 Dec 2025 03:33:06 -0000 1.223
+++ net/if.h 4 Mar 2026 14:47:53 -0000
@@ -232,6 +232,7 @@ struct if_status_description {
#define IFXF_AUTOCONF4 0x80 /* [N] v4 autoconf (aka dhcp) enabled */
#define IFXF_MONITOR 0x100 /* [N] only used for bpf */
#define IFXF_LRO 0x200 /* [N] TCP large recv offload */
+#define IFXF_MBUF_64BIT 0x400 /* [I] mbuf with 64 bit DMA supported */
#define IFXF_CANTCHANGE \
(IFXF_MPSAFE|IFXF_CLONED)
Index: sys/mbuf.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/sys/mbuf.h,v
diff -u -p -r1.269 mbuf.h
--- sys/mbuf.h 5 Feb 2026 03:26:00 -0000 1.269
+++ sys/mbuf.h 4 Mar 2026 14:50:42 -0000
@@ -441,6 +441,7 @@ void m_align(struct mbuf *, int);
struct mbuf *m_clget(struct mbuf *, int, u_int);
void m_extref(struct mbuf *, struct mbuf *);
void m_pool_init(struct pool *, u_int, u_int, const char *);
+void m_pool_noconstraints(void);
u_int m_pool_used(void);
void m_extfree_pool(caddr_t, u_int, void *);
void m_adj(struct mbuf *, int);
Index: uvm/uvm_extern.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/uvm/uvm_extern.h,v
diff -u -p -r1.187 uvm_extern.h
--- uvm/uvm_extern.h 13 Nov 2025 10:55:51 -0000 1.187
+++ uvm/uvm_extern.h 4 Mar 2026 14:50:42 -0000
@@ -358,6 +358,7 @@ extern const struct kmem_pa_mode kp_zero
extern const struct kmem_pa_mode kp_dma;
extern const struct kmem_pa_mode kp_dma_contig;
extern const struct kmem_pa_mode kp_dma_zero;
+extern const struct kmem_pa_mode kp_mbuf_contig;
extern const struct kmem_pa_mode kp_pageable;
extern const struct kmem_pa_mode kp_none;
Index: uvm/uvm_km.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/uvm/uvm_km.c,v
diff -u -p -r1.159 uvm_km.c
--- uvm/uvm_km.c 13 Nov 2025 10:55:51 -0000 1.159
+++ uvm/uvm_km.c 4 Mar 2026 14:50:42 -0000
@@ -745,6 +745,11 @@ const struct kmem_pa_mode kp_dma_zero =
.kp_zero = 1
};
+const struct kmem_pa_mode kp_mbuf_contig = {
+ .kp_constraint = &no_constraint,
+ .kp_maxseg = 1
+};
+
const struct kmem_pa_mode kp_zero = {
.kp_constraint = &no_constraint,
.kp_zero = 1
mbuf dma 64 bit