[RFC] arm64: extra entries in /proc/iomem for kexec
AKASHI Takahiro
takahiro.akashi at linaro.org
Wed Mar 14 21:41:11 PDT 2018
On Wed, Mar 14, 2018 at 08:39:23AM +0000, Ard Biesheuvel wrote:
> On 14 March 2018 at 08:29, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote:
> > In the last couples of months, there were some problems reported [1],[2]
> > around arm64 kexec/kdump. Where those phenomenon look different,
> > the root cause would be that kexec/kdump doesn't take into account
> > crucial "reserved" regions of system memory and unintentionally corrupts
> > them.
> >
> > Given that kexec-tools looks for all the information by seeking the file,
> > /proc/iomem, the first step to address said problems is to expand this file's
> > format so that it will have enough information about system memory and
> > its usage.
> >
> > Attached is my experimental code: With this patch applied, /proc/iomem sees
> > something like the below:
> >
> > (format A)
> > 40000000-5871ffff : System RAM
> > 40080000-40f1ffff : Kernel code
> > 41040000-411e8fff : Kernel data
> > 54400000-583fffff : Crash kernel
> > 58590000-585effff : EFI Resources
> > 58700000-5871ffff : EFI Resources
> > 58720000-58b5ffff : System RAM
> > 58720000-58b5ffff : EFI Resources
> > 58b60000-5be3ffff : System RAM
> > 58b61018-58b61947 : EFI Memory Map
> > 59a7b118-59a7b667 : EFI Configuration Tables
> > 5be40000-5becffff : System RAM <== (A-1)
> > 5be40000-5becffff : EFI Resources
> > 5bed0000-5bedffff : System RAM
> > 5bee0000-5bffffff : System RAM
> > 5bee0000-5bffffff : EFI Resources
> > 5c000000-5fffffff : System RAM
> > 8000000000-ffffffffff : PCI Bus 0000:00
> >
> > Meanwhile, the workaround I suggested in [3] gave us a simpler view:
> >
> > (format B)
> > 40000000-5871ffff : System RAM
> > 40080000-40f1ffff : Kernel code
> > 41040000-411e9fff : Kernel data
> > 54400000-583fffff : Crash kernel
> > 58590000-585effff : reserved
> > 58700000-5871ffff : reserved
> > 58720000-58b5ffff : reserved
> > 58b60000-5be3ffff : System RAM
> > 58b61000-58b61fff : reserved
> > 59a7b318-59a7b867 : reserved
> > 5be40000-5becffff : reserved <== (B-1)
> > 5bed0000-5bedffff : System RAM
> > 5bee0000-5bffffff : reserved
> > 5c000000-5fffffff : System RAM
> > 5ec00000-5edfffff : reserved
> > 8000000000-ffffffffff : PCI Bus 0000:00
> >
> > Here all the regions to be protected are named just "reserved" whether
> > they are NOMAP regions or simply-memblock_reserve'd. They are not very
> > useful for anything but kexec/kdump which knows what they mean.
> >
> > Alternatively, we may want to give them more specific names, based on
> > related efi memory map descriptors and else, that will characterize
> > their contents:
> >
> > (format C)
> > 40000000-5871ffff : System RAM
> > 40080000-40f1ffff : Kernel code
> > 41040000-411e9fff : Kernel data
> > 54400000-583fffff : Crash kernel
> > 58590000-585effff : ACPI Reclaim Memory
> > 58700000-5871ffff : ACPI Reclaim Memory
> > 58720000-58b5ffff : System RAM
> > 58720000-5878ffff : Runtime Data
> > 58790000-587dffff : Runtime Code
> > 587e0000-5882ffff : Runtime Data
> > 58830000-5887ffff : Runtime Code
> > 58880000-588cffff : Runtime Data
> > 588d0000-5891ffff : Runtime Code
> > 58920000-5896ffff : Runtime Data
> > 58970000-589bffff : Runtime Code
> > 589c0000-58a5ffff : Runtime Data
> > 58a60000-58abffff : Runtime Code
> > 58ac0000-58b0ffff : Runtime Data
> > 58b10000-58b5ffff : Runtime Code
> > 58b60000-5be3ffff : System RAM
> > 58b61000-58b61fff : EFI Memory Map
> > 59a7b118-59a7b667 : EFI Memory Attributes Table
> > 5be40000-5becffff : System RAM
> > 5be40000-5becffff : Runtime Code
> > 5bed0000-5bedffff : System RAM
> > 5bee0000-5bffffff : System RAM
> > 5bee0000-5bffffff : Runtime Data
> > 5c000000-5fffffff : System RAM
> > 8000000000-ffffffffff : PCI Bus 0000:00
> >
> > I once created a patch for this format, but it looks quite noisy and
> > names are a sort of mixture of memory attributes( ACPI Reclaim memory,
> > Conventional Memory, Persistent Memory etc.) vs.
> > function/usages ([Loader|Boot Service|Runtime] Code/Data).
> > (As a matter of fact, (C-1) consists of various ACPI tables.)
> > Anyhow, they seem not so useful for most of other applications.
> >
> > Those observations lead to format A, where some entries with the same
> > attributes are squeezed into a single entry under a simple name if they
> > are neighbouring.
> >
> >
> > So my questions here are:
> >
> > 1. Which format, A, B, or C, is the most appropriate for the moment?
> > or any other suggestions?
> >
>
> I think some variant of B should be sufficient. The only meaningful
> distinction between these reserved regions at a general level is
> whether they are NOMAP or not, so perhaps we can incorporate that.
I would definitely like to give your opinion the first priority,
but also hear from other guys.
Can you tell my why you think that the distinction, NOMAP or not,
is meaningful?
> As for identifying things like EFI configuration tables: this is a
> moving target, and we also define our own config tables for the TPM
> log, screeninfo on ARM etc. Also, for EFI memory types, you can boot
> with efi=debug and look at the entire memory map. So I think adding
> all that information may be overkill.
No doubt I agree.
The reason why I gave specific names to EFI configuration tables
is that all such tables are unambiguously listed in 'efi' structure,
while "screen info" seems to be arm-specific.
As for EFI memory types, I admit that they are inadequate for a source
of naming.
Nevertheless, I still have a sense that "reserved" sounds sloppy :)
> > Currently, there is a inconsistent view between (A) and the mainline's:
> > see (A-1) and (B-1). If this is really a matter, I can fix it.
> > Kexec-tools can be easily modified to accept both formats, though.
> >
> >
> > 2. How should we determine which regions be exported in /proc/iomem?
> >
> > a. Trust all the memblock_reserve'd regions as my previous patch [3] does.
> >
> > As I said, it's a kind of "overkill." Some of regions, say fdt, are
> > not required to be preserved across kexec.
> >
>
> I don't think there is anything wrong with listing all
> memblock_reserve()'d regions here, even if kexec has other means of
> ensuring that they are not touched.
I initially thought that one downside in this approach is that we might
not able to re-use a reserved region for fdt, as well as others also
dynamically reserved by "/reserved-memory/" nodes, after kexec and that
it would end up more or less a memory leak eventually after iterating
kexec()'s. But
after thinking twice, I now don't believe it is a problem anymore.
In kexec case, we won't have to hand over a list of reserved regions to
secondary kernel. Kdump, on the other hand, will be triggered only once
for its nature anyway.
> But as I said, I think it would be
> useful to distinguish them from NOMAP regions (even if the nesting
> below System RAM already shows that as well)
Something like "reserved (no map)"?
-Takahiro AKASHI
>
> > b. List regions separately and exhaustively later on at a single point
> > as my patch attached does.
> >
> > I'm afraid of any possibility that some regions may be doubly counted,
> > one from efi memory map search and another from other efi/acpi code
> > (various type of "tables" in most cases).
> >
> > c. Expand efi_mem_reserve() with an argument of "resource descriptor" and
> > replace memblock_reserve() in efi code wherever necessary so as to
> > maintain an export list.
> >
> > efi_mem_reserve() was first introduced for specific needs at kexec
> > on x86, but I believe that its coverage over efi code is far from perfect.
> >
> > [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-November/541831.html
> > [2] http://lkml.iu.edu//hypermail/linux/kernel/1802.2/06745.html
> > [3] http://lkml.iu.edu//hypermail/linux/kernel/1803.0/04658.html
> > http://lkml.iu.edu//hypermail/linux/kernel/1803.0/04659.html
> >
> > -Takahiro AKASHI
> >
> > ===8<===
> > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> > index 30ad2f085d1f..feda5cbdc6bf 100644
> > --- a/arch/arm64/kernel/setup.c
> > +++ b/arch/arm64/kernel/setup.c
> > @@ -214,13 +214,8 @@ static void __init request_standard_resources(void)
> >
> > for_each_memblock(memory, region) {
> > res = alloc_bootmem_low(sizeof(*res));
> > - if (memblock_is_nomap(region)) {
> > - res->name = "reserved";
> > - res->flags = IORESOURCE_MEM;
> > - } else {
> > - res->name = "System RAM";
> > - res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> > - }
> > + res->name = "System RAM";
> > + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> > res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
> > res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
> >
> > @@ -239,6 +234,9 @@ static void __init request_standard_resources(void)
> > request_resource(res, &crashk_res);
> > #endif
> > }
> > +
> > + /* Add firmware-reserved memory */
> > + efi_arch_request_resources();
> > }
> >
> > u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
> > diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> > index 80d1a885def5..308143e69db4 100644
> > --- a/drivers/firmware/efi/arm-init.c
> > +++ b/drivers/firmware/efi/arm-init.c
> > @@ -13,8 +13,10 @@
> >
> > #define pr_fmt(fmt) "efi: " fmt
> >
> > +#include <linux/bootmem.h>
> > #include <linux/efi.h>
> > #include <linux/init.h>
> > +#include <linux/ioport.h>
> > #include <linux/memblock.h>
> > #include <linux/mm_types.h>
> > #include <linux/of.h>
> > @@ -280,3 +282,97 @@ static int __init register_gop_device(void)
> > return PTR_ERR_OR_ZERO(pd);
> > }
> > subsys_initcall(register_gop_device);
> > +
> > +static unsigned long __init efi_memattr_to_iores_type(u64 addr)
> > +{
> > + if (efi_mem_attributes(addr) &
> > + (EFI_MEMORY_WB|EFI_MEMORY_WT|EFI_MEMORY_WC))
> > + return IORESOURCE_SYSTEM_RAM;
> > + else
> > + return IORESOURCE_MEM;
> > +}
> > +
> > +static unsigned long __init efi_type_to_iores_desc(u64 addr)
> > +{
> > + /* TODO */
> > + return IORES_DESC_NONE;
> > +}
> > +
> > +static struct resource * __init _efi_arch_request_resource(u64 start, u64 end,
> > + char *name, struct resource *prev)
> > +{
> > + struct resource *conflict, *res;
> > +
> > + res = alloc_bootmem_low(sizeof(*res));
> > +
> > + res->start = start;
> > + res->end = end;
> > + res->flags = efi_memattr_to_iores_type(res->start);
> > + res->desc = efi_type_to_iores_desc(res->start);
> > + res->name = name;
> > +
> > + conflict = request_resource_conflict(&iomem_resource, res);
> > + if (conflict) {
> > + if (prev && (prev->parent == conflict) &&
> > + ((prev->end + 1) == start)) {
> > + /* merge consecutive regions */
> > + adjust_resource(prev, prev->start,
> > + end - prev->start + 1);
> > + free_bootmem((unsigned long)res, sizeof(*res));
> > + res = prev;
> > + } else
> > + insert_resource(conflict, res);
> > + }
> > +
> > + return res;
> > +}
> > +
> > +/* Kexec expects those resources to be preserved */
> > +void __init efi_arch_request_resources(void)
> > +{
> > + struct resource *res = NULL;
> > + efi_memory_desc_t *md;
> > + u64 paddr, npages, size;
> > +
> > + /* EFI Memory Map */
> > + /* FIXME */
> > + _efi_arch_request_resource(efi.memmap.phys_map,
> > + efi.memmap.phys_map
> > + + efi.memmap.desc_size * efi.memmap.nr_map - 1,
> > + "EFI Memory Map", res);
> > +
> > + /* generic EFI Configuration Tables */
> > + efi_request_config_table_resources(_efi_arch_request_resource);
> > +
> > + /* architecture-specifc Configuration Tables */
> > + if (screen_info.lfb_size)
> > + _efi_arch_request_resource(screen_info.lfb_base,
> > + screen_info.lfb_base + screen_info.lfb_size - 1,
> > + "EFI Screen Info Table", res);
> > +
> > + /* architecture-specific EFI resources */
> > + /* FIXME */
> > + efi_memmap_install(efi.memmap.phys_map, efi.memmap.nr_map);
> > +
> > + res = NULL;
> > + for_each_efi_memory_desc(md) {
> > + paddr = md->phys_addr;
> > + npages = md->num_pages;
> > +
> > + memrange_efi_to_native(&paddr, &npages);
> > + size = npages << PAGE_SHIFT;
> > +
> > + if (is_memory(md)) {
> > + if (!is_usable_memory(md))
> > + res = _efi_arch_request_resource(paddr,
> > + paddr + size - 1,
> > + "EFI Resources", res);
> > +
> > + if (md->type == EFI_ACPI_RECLAIM_MEMORY)
> > + res = _efi_arch_request_resource(paddr,
> > + paddr + size - 1,
> > + "EFI Resources", res);
> > + }
> > + }
> > + efi_memmap_unmap();
> > +}
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index cd42f66a7c85..b13c9461278b 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -603,6 +603,33 @@ int __init efi_config_init(efi_config_table_type_t *arch_tables)
> > return ret;
> > }
> >
> > +void __init efi_request_config_table_resources(struct resource *(*fn)(u64 start,
> > + u64 end, char *name, struct resource *prev))
> > +{
> > + struct resource *prev = NULL;
> > + char *name = "EFI Configuration Tables";
> > +
> > + if (efi.config_table_size)
> > + prev = fn(efi.config_table,
> > + efi.config_table + efi.config_table_size - 1, name,
> > + prev);
> > +
> > + if (efi.mem_attr_table_size)
> > + prev = fn(efi.mem_attr_table,
> > + efi.mem_attr_table + efi.mem_attr_table_size - 1, name,
> > + prev);
> > +
> > + if (efi.esrt_size)
> > + prev = fn(efi.esrt, efi.esrt + efi.esrt_size - 1, name, prev);
> > +
> > + if (efi.tpm_log_size)
> > + prev = fn(efi.tpm_log, efi.tpm_log + efi.tpm_log_size - 1, name,
> > + prev);
> > +
> > +
> > + /* TODO: BGRT */
> > +}
> > +
> > #ifdef CONFIG_EFI_VARS_MODULE
> > static int __init efi_load_efivars(void)
> > {
> > diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
> > index c47e0c6ec00f..61f66c139afb 100644
> > --- a/drivers/firmware/efi/esrt.c
> > +++ b/drivers/firmware/efi/esrt.c
> > @@ -330,6 +330,7 @@ void __init efi_esrt_init(void)
> >
> > esrt_data = (phys_addr_t)efi.esrt;
> > esrt_data_size = size;
> > + efi.esrt_size = size;
> >
> > end = esrt_data + size;
> > pr_info("Reserving ESRT space from %pa to %pa.\n", &esrt_data, &end);
> > diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c
> > index 8986757eafaf..dc2c7608793a 100644
> > --- a/drivers/firmware/efi/memattr.c
> > +++ b/drivers/firmware/efi/memattr.c
> > @@ -42,6 +42,7 @@ int __init efi_memattr_init(void)
> > }
> >
> > tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
> > + efi.mem_attr_table_size = tbl_size;
> > memblock_reserve(efi.mem_attr_table, tbl_size);
> > set_bit(EFI_MEM_ATTR, &efi.flags);
> >
> > diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
> > index 0cbeb3d46b18..53cfb12513fa 100644
> > --- a/drivers/firmware/efi/tpm.c
> > +++ b/drivers/firmware/efi/tpm.c
> > @@ -33,6 +33,7 @@ int __init efi_tpm_eventlog_init(void)
> > }
> >
> > tbl_size = sizeof(*log_tbl) + log_tbl->size;
> > + efi.tpm_log_size = tbl_size;
> > memblock_reserve(efi.tpm_log, tbl_size);
> > early_memunmap(log_tbl, sizeof(*log_tbl));
> > return 0;
> > diff --git a/include/linux/efi.h b/include/linux/efi.h
> > index f5083aa72eae..9c3f8d284b36 100644
> > --- a/include/linux/efi.h
> > +++ b/include/linux/efi.h
> > @@ -942,11 +942,15 @@ extern struct efi {
> > unsigned long fw_vendor; /* fw_vendor */
> > unsigned long runtime; /* runtime table */
> > unsigned long config_table; /* config tables */
> > + unsigned long config_table_size;
> > unsigned long esrt; /* ESRT table */
> > + unsigned long esrt_size;
> > unsigned long properties_table; /* properties table */
> > unsigned long mem_attr_table; /* memory attributes table */
> > + unsigned long mem_attr_table_size;
> > unsigned long rng_seed; /* UEFI firmware random seed */
> > unsigned long tpm_log; /* TPM2 Event Log table */
> > + unsigned long tpm_log_size;
> > efi_get_time_t *get_time;
> > efi_set_time_t *set_time;
> > efi_get_wakeup_time_t *get_wakeup_time;
> > @@ -980,6 +984,9 @@ efi_guid_to_str(efi_guid_t *guid, char *out)
> > }
> >
> > extern void efi_init (void);
> > +extern void efi_arch_request_resources(void);
> > +extern void efi_request_config_table_resources(struct resource *
> > + (*fn)(u64 start, u64 end, char *name, struct resource *prev));
> > extern void *efi_get_pal_addr (void);
> > extern void efi_map_pal_code (void);
> > extern void efi_memmap_walk (efi_freemem_callback_t callback, void *arg);
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