Date: Wed, 8 Feb 2023 17:06:17 -0400 From: Mitchell Horne <mhorne@freebsd.org> To: Jessica Clarke <jrtc27@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: <d2156648-6181-6721-12e3-dae5ae15e49c@freebsd.org> In-Reply-To: <26339898-C02C-42D4-916A-2B6AD2562B02@freebsd.org> References: <202302082052.318KqOE6052473@gitrepo.freebsd.org> <26339898-C02C-42D4-916A-2B6AD2562B02@freebsd.org>
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On 2/8/23 16:55, Jessica Clarke wrote: > On 8 Feb 2023, at 20:52, Mitchell Horne <mhorne@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 <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 >> >> 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? >> 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 */ >
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