[PATCH] RISC-V: Add kernel image sections to the resource tree
Nick Kossifidis
mick at ics.forth.gr
Tue Dec 22 18:58:26 EST 2020
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. The
issue is that we call memblock_alloc() for the first time inside the
loop and for_each_mem_region() macro uses pointer arithmetic on the
initial array of reserved memblocks, we could use
for_each_memblock_type() macro but it's not on memblock.h anymore OR we
could call memblock_alloc() before the loop so that the array is not
expanded while itterating.
How about this, does it work for you ?:
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 1d85e9bf7..460cfddb7 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -127,8 +127,16 @@ static void __init init_resources(void)
{
struct memblock_region *region = NULL;
struct resource *res = NULL;
+ struct resource *mem_resources = NULL;
+ size_t mem_resources_sz = 0;
int ret = 0;
+ mem_resources_sz = memblock.memory.cnt * sizeof(struct resource);
+ mem_resources = memblock_alloc(mem_resources_sz, SMP_CACHE_BYTES);
+ if (!mem_resources)
+ panic("%s: Failed to allocate %zu bytes\n", __func__,
+ sizeof(struct resource));
+
code_res.start = __pa_symbol(_text);
code_res.end = __pa_symbol(_etext) - 1;
code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
@@ -171,20 +179,21 @@ static void __init init_resources(void)
* Ignore any other reserved regions within
* system memory.
*/
- if (memblock_is_memory(res->start))
+ if (memblock_is_memory(res->start)) {
+ memblock_free((phys_addr_t) res, sizeof(struct resource));
continue;
+ }
ret = add_resource(&iomem_resource, res);
- if (ret < 0)
+ if (ret < 0) {
+ memblock_free((phys_addr_t) res, sizeof(struct resource));
goto error;
+ }
}
/* 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_resources++;
if (unlikely(memblock_is_nomap(region))) {
res->name = "Reserved";
@@ -205,9 +214,9 @@ static void __init init_resources(void)
return;
error:
- memblock_free((phys_addr_t) res, sizeof(struct resource));
/* Better an empty resource tree than an inconsistent one */
release_child_resources(&iomem_resource);
+ memblock_free((phys_addr_t) mem_resources, mem_resources_sz);
}
Regards,
Nick
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