On 8 Feb 2023, at 21:06, Mitchell Horne <mho...@freebsd.org> wrote: > > On 2/8/23 16:55, Jessica Clarke wrote: >> On 8 Feb 2023, at 20:52, Mitchell Horne <mho...@freebsd.org> wrote: >>> >>> The branch main has been updated by mhorne: >>> >>> URL: >>> https://cgit.FreeBSD.org/src/commit/?id=e6cf1a0826c9d7f229e41224ec7b783501636528 >>> >>> commit e6cf1a0826c9d7f229e41224ec7b783501636528 >>> Author: Mitchell Horne <mho...@freebsd.org> >>> AuthorDate: 2021-05-27 14:27:40 +0000 >>> Commit: Mitchell Horne <mho...@freebsd.org> >>> CommitDate: 2023-02-08 20:50:46 +0000 >>> >>> physmem: add ram0 pseudo-driver >>> >>> Its purpose is to reserve all I/O space belonging to physical memory >> If it’s RAM then it’s not I/O, and if it’s I/O then it’s not RAM? >> Jess > > 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’t 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’t include them (which doesn’t *belong* to physical memory, just resides in the same address space), reserving FDT/ACPI-reserved actual RAM memory regions so SYS_RES_MEMORY doesn’t include them (which isn’t 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. >>> >>> If needed, the device can be disabled with hint.ram.0.disabled="1" in >>> /boot/device.hints. >>> >>> 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(-) >>> >>> 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("$FreeBSD$"); >>> >>> #include <sys/param.h> >>> #include <sys/systm.h> >>> +#include <sys/bus.h> >>> #include <sys/kernel.h> >>> +#include <sys/module.h> >>> #include <sys/physmem.h> >>> >>> #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 = atop(phys_avail[nextidx - 1]); >>> } >>> -#endif >>> >>> #ifdef DDB >>> #include <ddb/ddb.h> >>> @@ -536,3 +539,98 @@ DB_SHOW_COMMAND_FLAGS(physmem, db_show_physmem, >>> DB_CMD_MEMSAFE) >>> } >>> >>> #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) == 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 = 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 = 0; avail_list[i + 1] != 0; i += 2) { >>> + start = avail_list[i]; >>> + end = 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) == NULL) >>> + panic("ram_attach: resource %d failed to attach", rid); >>> + rid++; >>> + } >>> + >>> + /* Now, reserve the excluded memory regions. */ >>> + for (i = 0, hwp = exregions; i < excnt; i++, hwp++) { >>> + start = hwp->addr; >>> + end = 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) == NULL) { >>> + if (bootverbose) >>> + device_printf(dev, "failed to reserve >>> region\n"); >>> + continue; >>> + } >>> + rid++; >>> + } >>> + >>> + return (0); >>> +} >>> + >>> +static device_method_t ram_methods[] = { >>> + /* 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 */
