Date: Wed, 8 Feb 2023 21:13:28 +0000 From: Jessica Clarke <jrtc27@freebsd.org> To: Mitchell Horne <mhorne@freebsd.org> Cc: "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: e6cf1a0826c9 - main - physmem: add ram0 pseudo-driver Message-ID: <505D72C8-1F67-46C8-A6EF-39392841FBF5@freebsd.org> In-Reply-To: <d2156648-6181-6721-12e3-dae5ae15e49c@freebsd.org> References: <202302082052.318KqOE6052473@gitrepo.freebsd.org> <26339898-C02C-42D4-916A-2B6AD2562B02@freebsd.org> <d2156648-6181-6721-12e3-dae5ae15e49c@freebsd.org>
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On 8 Feb 2023, at 21:06, Mitchell Horne <mhorne@freebsd.org> wrote: >=20 > On 2/8/23 16:55, Jessica Clarke wrote: >> On 8 Feb 2023, at 20:52, Mitchell Horne <mhorne@FreeBSD.org> wrote: >>>=20 >>> The branch main has been updated by mhorne: >>>=20 >>> URL: = https://cgit.FreeBSD.org/src/commit/?id=3De6cf1a0826c9d7f229e41224ec7b7835= 01636528 >>>=20 >>> commit e6cf1a0826c9d7f229e41224ec7b783501636528 >>> Author: Mitchell Horne <mhorne@FreeBSD.org> >>> AuthorDate: 2021-05-27 14:27:40 +0000 >>> Commit: Mitchell Horne <mhorne@FreeBSD.org> >>> CommitDate: 2023-02-08 20:50:46 +0000 >>>=20 >>> physmem: add ram0 pseudo-driver >>>=20 >>> Its purpose is to reserve all I/O space belonging to physical = memory >> If it=E2=80=99s RAM then it=E2=80=99s not I/O, and if it=E2=80=99s = I/O then it=E2=80=99s not RAM? >> Jess >=20 > Yes, they are distinct. And yet, they share an address space. So this = is to assist in the SYS_RES_MEMORY resource bookkeeping. Did I misuse = some terminology, or what is your actual question? The commit message just doesn=E2=80=99t make sense to me, it switches = between talking about I/O space and memory (same applies to the comments in the code). Is this reserving I/O parts of the address space so SYS_RES_MEMORY doesn=E2=80=99t include them (which doesn=E2=80=99t = *belong* to physical memory, just resides in the same address space), reserving FDT/ACPI-reserved actual RAM memory regions so SYS_RES_MEMORY doesn=E2=80=99= t include them (which isn=E2=80=99t I/O space), or both? Currently it = reads to me as describing part of one and part of the other, but neither fully. Jess >>> from nexus, preventing it from being handed out by = bus_alloc_resource() >>> to callers such as xenpv_alloc_physmem(), which looks for the = first >>> available free range it can get. This mimics the existing = pseudo-driver >>> on x86. >>>=20 >>> If needed, the device can be disabled with = hint.ram.0.disabled=3D"1" in >>> /boot/device.hints. >>>=20 >>> Reviewed by: imp >>> MFC after: 1 month >>> Differential Revision: https://reviews.freebsd.org/D32343 >>> --- >>> sys/kern/subr_physmem.c | 100 = +++++++++++++++++++++++++++++++++++++++++++++++- >>> 1 file changed, 99 insertions(+), 1 deletion(-) >>>=20 >>> diff --git a/sys/kern/subr_physmem.c b/sys/kern/subr_physmem.c >>> index 498ad2440f40..bb6af5a580aa 100644 >>> --- a/sys/kern/subr_physmem.c >>> +++ b/sys/kern/subr_physmem.c >>> @@ -40,7 +40,9 @@ __FBSDID("$FreeBSD$"); >>>=20 >>> #include <sys/param.h> >>> #include <sys/systm.h> >>> +#include <sys/bus.h> >>> #include <sys/kernel.h> >>> +#include <sys/module.h> >>> #include <sys/physmem.h> >>>=20 >>> #ifdef _KERNEL >>> @@ -49,7 +51,9 @@ __FBSDID("$FreeBSD$"); >>> #include <vm/vm_page.h> >>> #include <vm/vm_phys.h> >>> #include <vm/vm_dumpset.h> >>> + >>> #include <machine/md_var.h> >>> +#include <machine/resource.h> >>> #else >>> #include <stdarg.h> >>> #include <stdio.h> >>> @@ -524,7 +528,6 @@ physmem_init_kernel_globals(void) >>> panic("No memory entries in phys_avail"); >>> Maxmem =3D atop(phys_avail[nextidx - 1]); >>> } >>> -#endif >>>=20 >>> #ifdef DDB >>> #include <ddb/ddb.h> >>> @@ -536,3 +539,98 @@ DB_SHOW_COMMAND_FLAGS(physmem, db_show_physmem, = DB_CMD_MEMSAFE) >>> } >>>=20 >>> #endif /* DDB */ >>> + >>> +/* >>> + * ram pseudo driver - this reserves I/O space resources = corresponding to physical >>> + * memory regions. >>> + */ >>> + >>> +static void >>> +ram_identify(driver_t *driver, device_t parent) >>> +{ >>> + >>> + if (resource_disabled("ram", 0)) >>> + return; >>> + if (BUS_ADD_CHILD(parent, 0, "ram", 0) =3D=3D NULL) >>> + panic("ram_identify"); >>> +} >>> + >>> +static int >>> +ram_probe(device_t dev) >>> +{ >>> + >>> + device_quiet(dev); >>> + device_set_desc(dev, "System RAM"); >>> + return (BUS_PROBE_SPECIFIC); >>> +} >>> + >>> +static int >>> +ram_attach(device_t dev) >>> +{ >>> + vm_paddr_t avail_list[PHYS_AVAIL_COUNT]; >>> + rman_res_t start, end; >>> + struct region *hwp; >>> + int rid, i; >>> + >>> + rid =3D 0; >>> + >>> + /* Get the avail list. */ >>> + bzero(avail_list, sizeof(avail_list)); >>> + regions_to_avail(avail_list, EXFLAG_NOALLOC | EXFLAG_NODUMP, >>> + PHYS_AVAIL_COUNT, 0, NULL, NULL); >>> + >>> + /* Reserve all memory regions. */ >>> + for (i =3D 0; avail_list[i + 1] !=3D 0; i +=3D 2) { >>> + start =3D avail_list[i]; >>> + end =3D avail_list[i + 1]; >>> + >>> + if (bootverbose) >>> + device_printf(dev, >>> + "reserving memory region: %jx-%jx\n", >>> + (uintmax_t)start, (uintmax_t)end); >>> + >>> + if (bus_alloc_resource(dev, SYS_RES_MEMORY, &rid, start, = end, >>> + end - start, 0) =3D=3D NULL) >>> + panic("ram_attach: resource %d failed to = attach", rid); >>> + rid++; >>> + } >>> + >>> + /* Now, reserve the excluded memory regions. */ >>> + for (i =3D 0, hwp =3D exregions; i < excnt; i++, hwp++) { >>> + start =3D hwp->addr; >>> + end =3D hwp->addr + hwp->size; >>> + >>> + if (bootverbose) >>> + device_printf(dev, >>> + "reserving excluded region: %jx-%jx\n", >>> + (uintmax_t)start, (uintmax_t)(end - 1)); >>> + >>> + /* >>> + * Best-effort attempt to reserve the range. This may = fail, as >>> + * sometimes the excluded ranges provided by the device = tree >>> + * will cover or overlap some I/O range. >>> + */ >>> + if (bus_alloc_resource(dev, SYS_RES_MEMORY, &rid, start, = end, >>> + end - start, 0) =3D=3D NULL) { >>> + if (bootverbose) >>> + device_printf(dev, "failed to reserve = region\n"); >>> + continue; >>> + } >>> + rid++; >>> + } >>> + >>> + return (0); >>> +} >>> + >>> +static device_method_t ram_methods[] =3D { >>> + /* Device interface */ >>> + DEVMETHOD(device_identify, ram_identify), >>> + DEVMETHOD(device_probe, ram_probe), >>> + DEVMETHOD(device_attach, ram_attach), >>> + >>> + DEVMETHOD_END >>> +}; >>> + >>> +DEFINE_CLASS_0(ram, ram_driver, ram_methods, /* no softc */ 1); >>> +DRIVER_MODULE(ram, nexus, ram_driver, 0, 0); >>> +#endif /* _KERNEL */
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