[PATCH] RISC-V: Add kernel image sections to the resource tree
Nick Kossifidis
mick at ics.forth.gr
Wed Dec 23 20:16:28 EST 2020
Στις 2020-12-24 01:32, Atish Patra έγραψε:
> On Wed, Dec 23, 2020 at 1:17 PM Atish Patra <atishp at atishpatra.org>
> wrote:
>>
>> On Wed, Dec 23, 2020 at 12:02 PM Atish Patra <atishp at atishpatra.org>
>> wrote:
>> >
>> > On Tue, Dec 22, 2020 at 3:59 PM Nick Kossifidis <mick at ics.forth.gr> wrote:
>> > >
>> > > Στις 2020-12-19 01:52, Atish Patra έγραψε:
>> > > > On Thu, Nov 5, 2020 at 10:37 AM Palmer Dabbelt <palmer at dabbelt.com>
>> > > > wrote:
>> > > >>
>> > > >> On Mon, 12 Oct 2020 07:24:10 PDT (-0700), mick at ics.forth.gr wrote:
>> > > >> > This patch (previously part of my kexec/kdump series) populates
>> > > >> > /proc/iomem with the various sections of the kernel image. We need
>> > > >> > this for kexec-tools to be able to prepare the crashkernel image
>> > > >> > for kdump to work. Since resource tree initialization is not
>> > > >> > related to memory initialization I added the code to kernel/setup.c
>> > > >> > and removed the original code (derived from the arm64 tree) from
>> > > >> > mm/init.c.
>> > > >> >
>> > > >> > Signed-off-by: Nick Kossifidis <mick at ics.forth.gr>
>> > > >> > ---
>> > > >> > arch/riscv/kernel/setup.c | 160 ++++++++++++++++++++++++++++++++++++++
>> > > >> > arch/riscv/mm/init.c | 27 -------
>> > > >> > 2 files changed, 160 insertions(+), 27 deletions(-)
>> > > >> >
>> > > >> > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>> > > >> > index 2c6dd3293..450f0142f 100644
>> > > >> > --- a/arch/riscv/kernel/setup.c
>> > > >> > +++ b/arch/riscv/kernel/setup.c
>> > > >> > @@ -4,6 +4,8 @@
>> > > >> > * Chen Liqin <liqin.chen at sunplusct.com>
>> > > >> > * Lennox Wu <lennox.wu at sunplusct.com>
>> > > >> > * Copyright (C) 2012 Regents of the University of California
>> > > >> > + * Copyright (C) 2020 FORTH-ICS/CARV
>> > > >> > + * Nick Kossifidis <mick at ics.forth.gr>
>> > > >> > */
>> > > >> >
>> > > >> > #include <linux/init.h>
>> > > >> > @@ -48,6 +50,163 @@ atomic_t hart_lottery __section(.sdata);
>> > > >> > unsigned long boot_cpu_hartid;
>> > > >> > static DEFINE_PER_CPU(struct cpu, cpu_devices);
>> > > >> >
>> > > >> > +/*
>> > > >> > + * Place kernel memory regions on the resource tree so that
>> > > >> > + * kexec-tools can retrieve them from /proc/iomem. While there
>> > > >> > + * also add "System RAM" regions for compatibility with other
>> > > >> > + * archs, and the rest of the known regions for completeness.
>> > > >> > + */
>> > > >> > +static struct resource code_res = { .name = "Kernel code", };
>> > > >> > +static struct resource data_res = { .name = "Kernel data", };
>> > > >> > +static struct resource rodata_res = { .name = "Kernel rodata", };
>> > > >> > +static struct resource bss_res = { .name = "Kernel bss", };
>> > > >> > +
>> > > >> > +static int __init add_resource(struct resource *parent,
>> > > >> > + struct resource *res)
>> > > >> > +{
>> > > >> > + int ret = 0;
>> > > >> > +
>> > > >> > + ret = insert_resource(parent, res);
>> > > >> > + if (ret < 0) {
>> > > >> > + pr_err("Failed to add a %s resource at %llx\n",
>> > > >> > + res->name, (unsigned long long) res->start);
>> > > >> > + return ret;
>> > > >> > + }
>> > > >> > +
>> > > >> > + return 1;
>> > > >> > +}
>> > > >> > +
>> > > >> > +static int __init add_kernel_resources(struct resource *res)
>> > > >> > +{
>> > > >> > + int ret = 0;
>> > > >> > +
>> > > >> > + /*
>> > > >> > + * The memory region of the kernel image is continuous and
>> > > >> > + * was reserved on setup_bootmem, find it here and register
>> > > >> > + * it as a resource, then register the various segments of
>> > > >> > + * the image as child nodes
>> > > >> > + */
>> > > >> > + if (!(res->start <= code_res.start && res->end >= data_res.end))
>> > > >> > + return 0;
>> > > >> > +
>> > > >> > + res->name = "Kernel image";
>> > > >> > + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >> > +
>> > > >> > + /*
>> > > >> > + * We removed a part of this region on setup_bootmem so
>> > > >> > + * we need to expand the resource for the bss to fit in.
>> > > >> > + */
>> > > >> > + res->end = bss_res.end;
>> > > >> > +
>> > > >> > + ret = add_resource(&iomem_resource, res);
>> > > >> > + if (ret < 0)
>> > > >> > + return ret;
>> > > >> > +
>> > > >> > + ret = add_resource(res, &code_res);
>> > > >> > + if (ret < 0)
>> > > >> > + return ret;
>> > > >> > +
>> > > >> > + ret = add_resource(res, &rodata_res);
>> > > >> > + if (ret < 0)
>> > > >> > + return ret;
>> > > >> > +
>> > > >> > + ret = add_resource(res, &data_res);
>> > > >> > + if (ret < 0)
>> > > >> > + return ret;
>> > > >> > +
>> > > >> > + ret = add_resource(res, &bss_res);
>> > > >> > +
>> > > >> > + return ret;
>> > > >> > +}
>> > > >> > +
>> > > >> > +static void __init init_resources(void)
>> > > >> > +{
>> > > >> > + struct memblock_region *region = NULL;
>> > > >> > + struct resource *res = NULL;
>> > > >> > + int ret = 0;
>> > > >> > +
>> > > >> > + code_res.start = __pa_symbol(_text);
>> > > >> > + code_res.end = __pa_symbol(_etext) - 1;
>> > > >> > + code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >> > +
>> > > >> > + rodata_res.start = __pa_symbol(__start_rodata);
>> > > >> > + rodata_res.end = __pa_symbol(__end_rodata) - 1;
>> > > >> > + rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >> > +
>> > > >> > + data_res.start = __pa_symbol(_data);
>> > > >> > + data_res.end = __pa_symbol(_edata) - 1;
>> > > >> > + data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >> > +
>> > > >> > + bss_res.start = __pa_symbol(__bss_start);
>> > > >> > + bss_res.end = __pa_symbol(__bss_stop) - 1;
>> > > >> > + bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >> > +
>> > > >> > + /*
>> > > >> > + * Start by adding the reserved regions, if they overlap
>> > > >> > + * with /memory regions, insert_resource later on will take
>> > > >> > + * care of it.
>> > > >> > + */
>> > > >> > + for_each_memblock(reserved, region) {
>> > > >> > + res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
>> > > >
>> > > > Is there a specific reason to invoke memblock_alloc while iterating
>> > > > reserved regions ?
>> > > > memblock_alloc also adds calls memblock_reserve. So we are modifying
>> > > > the reserved region entries
>> > > > while iterating it. It resulted in below warning for rv32.
>> > > >
>> > > > [ 0.000000] ------------[ cut here ]------------
>> > > > [ 0.000000] WARNING: CPU: 0 PID: 0 at kernel/resource.c:795
>> > > > __insert_resource+0x8e/0xd0
>> > > > [ 0.000000] Modules linked in:
>> > > > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
>> > > > 5.10.0-00022-ge20097fb37e2-dirty #549
>> > > > [ 0.000000] epc: c00125c2 ra : c001262c sp : c1c01f50
>> > > > [ 0.000000] gp : c1d456e0 tp : c1c0a980 t0 : ffffcf20
>> > > > [ 0.000000] t1 : 00000000 t2 : 00000000 s0 : c1c01f60
>> > > > [ 0.000000] s1 : ffffcf00 a0 : ffffff00 a1 : c1c0c0c4
>> > > > [ 0.000000] a2 : 80c12b15 a3 : 80402000 a4 : 80402000
>> > > > [ 0.000000] a5 : c1c0c0c4 a6 : 80c12b15 a7 : f5faf600
>> > > > [ 0.000000] s2 : c1c0c0c4 s3 : c1c0e000 s4 : c1009a80
>> > > > [ 0.000000] s5 : c1c0c000 s6 : c1d48000 s7 : c1613b4c
>> > > > [ 0.000000] s8 : 00000fff s9 : 80000200 s10: c1613b40
>> > > > [ 0.000000] s11: 00000000 t3 : c1d4a000 t4 : ffffffff
>> > > > [ 0.000000] t5 : c1008e38 t6 : 00000001
>> > > > [ 0.000000] status: 00000100 badaddr: 00000000 cause: 00000003
>> > > > [ 0.000000] irq event stamp: 0
>> > > > [ 0.000000] hardirqs last enabled at (0): [<00000000>] 0x0
>> > > > [ 0.000000] hardirqs last disabled at (0): [<00000000>] 0x0
>> > > > [ 0.000000] softirqs last enabled at (0): [<00000000>] 0x0
>> > > > [ 0.000000] softirqs last disabled at (0): [<00000000>] 0x0
>> > > > [ 0.000000] random: get_random_bytes called from __warn+0xd8/0x11e
>> > > > with crng_init=0
>> > > > [ 0.000000] ---[ end trace 0000000000000000 ]---
>> > > > [ 0.000000] Failed to add a Kernel code resource at 80402000
>> > > >
>> > > > Here is the fix that works:
>> > > > --- a/arch/riscv/kernel/setup.c
>> > > > +++ b/arch/riscv/kernel/setup.c
>> > > > @@ -127,7 +127,9 @@ static void __init init_resources(void)
>> > > > {
>> > > > struct memblock_region *region = NULL;
>> > > > struct resource *res = NULL;
>> > > > - int ret = 0;
>> > > > + int ret = 0, i = 0;
>> > > > + int num_mem_res;
>> > > > + struct resource *mem_res;
>> > > >
>> > > > code_res.start = __pa_symbol(_text);
>> > > > code_res.end = __pa_symbol(_etext) - 1;
>> > > > @@ -145,16 +147,17 @@ static void __init init_resources(void)
>> > > > bss_res.end = __pa_symbol(__bss_stop) - 1;
>> > > > bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>> > > >
>> > > > + num_mem_res = memblock.memory.cnt + memblock.reserved.cnt;
>> > > > + mem_res = memblock_alloc(num_mem_res * sizeof(*mem_res),
>> > > > SMP_CACHE_BYTES);
>> > > > + if (!mem_res)
>> > > > + panic("%s: Failed to allocate %zu bytes\n", __func__,
>> > > > num_mem_res * sizeof(*mem_res));
>> > > > /*
>> > > > * Start by adding the reserved regions, if they overlap
>> > > > * with /memory regions, insert_resource later on will take
>> > > > * care of it.
>> > > > */
>> > > > for_each_reserved_mem_region(region) {
>> > > > - res = memblock_alloc(sizeof(struct resource),
>> > > > SMP_CACHE_BYTES);
>> > > > - if (!res)
>> > > > - panic("%s: Failed to allocate %zu bytes\n",
>> > > > __func__,
>> > > > - sizeof(struct resource));
>> > > > + res = &mem_res[i++];
>> > > >
>> > > > res->name = "Reserved";
>> > > > res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
>> > > > @@ -181,11 +184,8 @@ static void __init init_resources(void)
>> > > >
>> > > > /* Add /memory regions to the resource tree */
>> > > > for_each_mem_region(region) {
>> > > > - res = memblock_alloc(sizeof(struct resource),
>> > > > SMP_CACHE_BYTES);
>> > > > - if (!res)
>> > > > - panic("%s: Failed to allocate %zu bytes\n",
>> > > > __func__,
>> > > > - sizeof(struct resource));
>> > > >
>> > > > + res = &mem_res[i++];
>> > > >
>> > > > If this looks okay to you, I will send the patch.
>> > > >
>> > >
>> > > The problem is that we don't want to include all reserved regions within
>> > > /memory such as the device tree or initramfs, since they'll get modified
>> > > and/or freed later on. So pre-allocating resources for all reserved
>> > > regions doesn't seem the right thing to do. My goal here was to allocate
>> > > a resource on each itteration and free it if not needed / on failure, I
>> > > free the failed resource on failure but not if it's not needed as you
>> > > noted.
>> > >
>> > > As for the issue of memblock_alloc() calling memblock_reserve(), we
>> > > don't add any new reserved regions at this point directly through
>> > > memblock_reserve(), and memblock_reserve() will run on neighboring
>> > > regions that memblock_merge_regions() will later on merge together, so
>> > > it'll work on a single growing region instead of creating new ones.
>>
>> Forgot to add this:
>> The contiguous region memory allocation and merging happens for RV64
>> but doesn't happen for RV32.
>> Here is a boot log with additional printk messages which clearly
>> indicate that memory regions are not contiguous.
>>
>> [ 0.000000] memblock_reserve: [0xc03fff80-0xc03fffff]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03fff40-0xc03fff5f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 5
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03fff00-0xc03fff1f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 6
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffec0-0xc03ffedf]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 7
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffe80-0xc03ffe9f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 8
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffe40-0xc03ffe5f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 9
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffe00-0xc03ffe1f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 10
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffdc0-0xc03ffddf]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 11
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffd80-0xc03ffd9f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 12
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffd40-0xc03ffd5f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 13
>> [ 0.000000] memblock_alloc_try_nid: 32 bytes align=0x40 nid=-1
>> from=0x00000000 max_addr=0x00000000 setup_arch+0x19c/0x3fe
>> [ 0.000000] memblock_reserve: [0xc03ffd00-0xc03ffd1f]
>> memblock_alloc_range_nid+0xa8/0x112
>> [ 0.000000] init_resources: resvd region memory.cnt 1 reserved.cnt
>> 14
>>
>> I am looking into the memblock allocation code to find out if this is
>> expected.
>>
>
> Ahh found it. memblock_align is called with SMP_CACHE_BYTES (64) bytes
> alignment.
> Using a 32byte alignment solves the memory resource warning I was
> seeing on RV32 boot.
>
> I still prefer one time allocation before the loop instead of
> memblock_alloc invocation
> in every iteration (both mem_region & reserved_mem_region). This is
> happening during boot time.
> The less work it does, it is better. Let me know if you think there
> are any downsides to this approach.
>
> Otherwise, I will revise my patch and send it.
>
ACK, we'll loose some memory for the reserved regions we'll ignore but
it's safer / simpler that way.
Thanks for debugging this, I guess we'll need a patch for the
SMP_CACHE_BYTES issue, we'll need a cache.h.
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