From nobody Wed Feb 8 22:26:25 2023 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4PBvjy4p2rz3n20m; Wed, 8 Feb 2023 22:26:46 +0000 (UTC) (envelope-from mhorne@freebsd.org) Received: from smtp.freebsd.org (smtp.freebsd.org [96.47.72.83]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4PBvjy4G6fz3wrR; Wed, 8 Feb 2023 22:26:46 +0000 (UTC) (envelope-from mhorne@freebsd.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1675895206; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=poIoXZ2e05sKkODcaDmGzcW4kZ7LMtg+Wv/bl5mb3Ic=; b=X09zqpgxTnEW+dq5hCRc5/kSs0vTLEaI3o2Hs+oXpGJZTEgBF5MxPvcaNufWt2RP36/oW0 OrnBWr6mDoek9iBcvNEE2EtXcD3EwE8I5HE3Gq/9GO3igKdwyqY3yoNi7Nh80xUpRJ7cRy Mjmz7J+rCZvkcgIc1Oz9HcPa/sAf1SwbXzcz7tTQNc+f8r9mZqfqKQF5i2kbwpFHWjNdtQ F7cbFWFlKJZ+9vYZNY5LXX4rcFOkhLM0VyNx3wN0OCiRNhbuVP6pl1TjiLOmLLh/C3SsrQ cg8r9SQ4L/T4agW7DDGZXCbjTfmRA4G0tx2bjsGVxhyJufmLO0QTN67KxisGLA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1675895206; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=poIoXZ2e05sKkODcaDmGzcW4kZ7LMtg+Wv/bl5mb3Ic=; b=TWaGtjBi+VhikW0lsQlHrUAIqtH6g8Gvw+KRouGW7OoXRzXGgkTQ0ZAJbiWTnv2no3XK+A l4JBu4nxB7rd94t7irVNVoKsBSVFnE4wnOBIa43bfuTEHFprWrORNY72g6JaUqesNiJdYk w3pOOAm2RJBmpXPYI6R+7FhRiW9NfBkIWEdwWYHXo+MDYpiaFwznHQhaI6BptrJZCXn9P5 o5SEaAZg8V/ACg5WVM7i9eBzBIHRTZPBvoefDcdIdL+jA7WAANiVnQZ3ug16oi87Fym/WT 20ge6379uXp3tPZGcgkOc3aKLgZepoiVflYEl69egMdCxbe6p9CkEufaoQYcbg== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1675895206; a=rsa-sha256; cv=none; b=O/PgPyjNCd2wRKqGMhxvQ8dwYuGrNPMJoT5N67fKaaE+2hs4Fy2TXj7JWa8BoImay0XczL eEG0uNThWCq130HfpPh47/CR4bDfDO8me/RjdhymdUakxbOGII9zREhvW1Ep71/jOPcdUj sbzTDvf7AFS2jSfBtokqHotmfLuCeqrvyqwtwRy9QH28eSJubLhN3+3LbmtxJkfDND+L4Q cYbL1g+5siiWa5lKi5IrAHoeND+FLN60auZq/xHZ1krWuJDw6/tjQZlc+2LKucJJtTg4Kr t7M5181Jr63U7MtVI5y2gJ5YonQILtBxSUw4KiGqBoZX3jJDM6cTeA83yFFiHQ== Received: from [192.168.1.151] (host-173-212-76-127.public.eastlink.ca [173.212.76.127]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mhorne) by smtp.freebsd.org (Postfix) with ESMTPSA id 4PBvjy1Shwz15LR; Wed, 8 Feb 2023 22:26:45 +0000 (UTC) (envelope-from mhorne@freebsd.org) Message-ID: <5cfc2de7-4b08-283b-b9fc-c990f236ff3e@freebsd.org> Date: Wed, 8 Feb 2023 18:26:25 -0400 List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: git: e6cf1a0826c9 - main - physmem: add ram0 pseudo-driver Content-Language: en-CA To: Jessica Clarke Cc: "src-committers@freebsd.org" , "dev-commits-src-all@freebsd.org" , "dev-commits-src-main@freebsd.org" References: <202302082052.318KqOE6052473@gitrepo.freebsd.org> <26339898-C02C-42D4-916A-2B6AD2562B02@freebsd.org> <505D72C8-1F67-46C8-A6EF-39392841FBF5@freebsd.org> From: Mitchell Horne In-Reply-To: <505D72C8-1F67-46C8-A6EF-39392841FBF5@freebsd.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ThisMailContainsUnwantedMimeParts: N On 2/8/23 17:13, Jessica Clarke wrote: > On 8 Feb 2023, at 21:06, Mitchell Horne wrote: >> >> On 2/8/23 16:55, Jessica Clarke wrote: >>> On 8 Feb 2023, at 20:52, Mitchell Horne wrote: >>>> >>>> The branch main has been updated by mhorne: >>>> >>>> URL: https://cgit.FreeBSD.org/src/commit/?id=e6cf1a0826c9d7f229e41224ec7b783501636528 >>>> >>>> commit e6cf1a0826c9d7f229e41224ec7b783501636528 >>>> Author: Mitchell Horne >>>> AuthorDate: 2021-05-27 14:27:40 +0000 >>>> Commit: Mitchell Horne >>>> 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 Okay sure, perhaps the term I am searching for but missing is "physical address space". We know that some regions of physical address space correspond to RAM/memory/"physical memory". Other portions of the address space correspond to memory-mapped I/O regions belonging to one or more devices. Device drivers allocate SYS_RES_MEMORY resources using e.g. bus_alloc_resource(). They do this to declare ownership of the particular range of physical address space that they will use for I/O. If it's not RF_SHAREABLE, then it can't be handed out again. Memory/RAM is handed out by a different set of APIs, and therefore never touches SYS_RES_MEMORY resources. However, it is true that the (tangible) physical memory in the system maps to a set of regions in the (abstract) physical address space. This is the sense in which I used the word "belong". The purpose of the change is to reserve, from the system-wide SYS_RES_MEMORY rman, those portions of the physical address space that correspond to real physical memory/RAM. > >>>> 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 >>>> #include >>>> +#include >>>> #include >>>> +#include >>>> #include >>>> >>>> #ifdef _KERNEL >>>> @@ -49,7 +51,9 @@ __FBSDID("$FreeBSD$"); >>>> #include >>>> #include >>>> #include >>>> + >>>> #include >>>> +#include >>>> #else >>>> #include >>>> #include >>>> @@ -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 >>>> @@ -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 */ >