| Message ID | 20180723015732.24252-2-takahiro.akashi@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kexec, kdump: fix boot failures on acpi-only system | expand |
On Sun, Jul 22, 2018 at 6:57 PM, AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > From: James Morse <james.morse@arm.com> > > There has been some confusion around what is necessary to prevent kexec > overwriting important memory regions. memblock: reserve, or nomap? > Only memblock nomap regions are reported via /proc/iomem, kexec's > user-space doesn't know about memblock_reserve()d regions. > > Until commit f56ab9a5b73ca ("efi/arm: Don't mark ACPI reclaim memory > as MEMBLOCK_NOMAP") the ACPI tables were nomap, now they are reserved > and thus possible for kexec to overwrite with the new kernel or initrd. > But this was always broken, as the UEFI memory map is also reserved > and not marked as nomap. > > Exporting both nomap and reserved memblock types is a nuisance as > they live in different memblock structures which we can't walk at > the same time. > > Take a second walk over memblock.reserved and add new 'reserved' > subnodes for the memblock_reserved() regions that aren't already > described by the existing code. (e.g. Kernel Code) > > We use reserve_region_with_split() to find the gaps in existing named > regions. This handles the gap between 'kernel code' and 'kernel data' > which is memblock_reserve()d, but already partially described by > request_standard_resources(). e.g.: > | 80000000-dfffffff : System RAM > | 80080000-80ffffff : Kernel code > | 81000000-8158ffff : reserved > | 81590000-8237efff : Kernel data > | a0000000-dfffffff : Crash kernel > | e00f0000-f949ffff : System RAM > > reserve_region_with_split needs kzalloc() which isn't available when > request_standard_resources() is called, use an initcall. > > Reported-by: Bhupesh Sharma <bhsharma@redhat.com> > Reported-by: Tyler Baicar <tbaicar@codeaurora.org> > Suggested-by: Akashi Takahiro <takahiro.akashi@linaro.org> > Signed-off-by: James Morse <james.morse@arm.com> > Fixes: d28f6df1305a ("arm64/kexec: Add core kexec support") > Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > CC: Mark Rutland <mark.rutland@arm.com> > --- > arch/arm64/kernel/setup.c | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c > index 30ad2f085d1f..5b4fac434c84 100644 > --- a/arch/arm64/kernel/setup.c > +++ b/arch/arm64/kernel/setup.c > @@ -241,6 +241,44 @@ static void __init request_standard_resources(void) > } > } > > +static int __init reserve_memblock_reserved_regions(void) > +{ > + phys_addr_t start, end, roundup_end = 0; > + struct resource *mem, *res; > + u64 i; > + > + for_each_reserved_mem_region(i, &start, &end) { > + if (end <= roundup_end) > + continue; /* done already */ > + > + start = __pfn_to_phys(PFN_DOWN(start)); > + end = __pfn_to_phys(PFN_UP(end)) - 1; > + roundup_end = end; > + > + res = kzalloc(sizeof(*res), GFP_ATOMIC); > + if (WARN_ON(!res)) > + return -ENOMEM; > + res->start = start; > + res->end = end; > + res->name = "reserved"; > + res->flags = IORESOURCE_MEM; > + > + mem = request_resource_conflict(&iomem_resource, res); > + /* > + * We expected memblock_reserve() regions to conflict with > + * memory created by request_standard_resources(). > + */ > + if (WARN_ON_ONCE(!mem)) > + continue; > + kfree(res); > + > + reserve_region_with_split(mem, start, end, "reserved"); > + } > + > + return 0; > +} > +arch_initcall(reserve_memblock_reserved_regions); > + Since this patch landed, on the HiKey board at bootup I'm seeing: [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions+0xd4/0x13c [ 0.451896] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.18.0-10758-ga534dc3 #709 [ 0.451903] Hardware name: HiKey Development Board (DT) [ 0.451913] pstate: 80400005 (Nzcv daif +PAN -UAO) [ 0.451922] pc : reserve_memblock_reserved_regions+0xd4/0x13c [ 0.451931] lr : reserve_memblock_reserved_regions+0xcc/0x13c [ 0.451938] sp : ffffff8008053d30 [ 0.451945] x29: ffffff8008053d30 x28: ffffff8008ebe650 [ 0.451957] x27: ffffff8008ead060 x26: ffffff8008e113b0 [ 0.451969] x25: 0000000000000000 x24: 0000000000488020 [ 0.451981] x23: 0000000021ffffff x22: ffffff8008e0d860 [ 0.451993] x21: ffffff8008d74370 x20: ffffff8009019000 [ 0.452005] x19: ffffffc07507a400 x18: ffffff8009019a48 [ 0.452017] x17: 0000000000000000 x16: 0000000000000000 [ 0.452028] x15: ffffff80890e973f x14: 0000000000000006 [ 0.452040] x13: 0000000000000000 x12: 0000000000000000 [ 0.452051] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f [ 0.452063] x9 : 0000000000000000 x8 : ffffffc07507a480 [ 0.452074] x7 : 0000000000000000 x6 : ffffffc07ffffc30 [ 0.452086] x5 : 0000000000000000 x4 : 0000000021ffffff [ 0.452097] x3 : 0000000000000001 x2 : 0000000000000001 [ 0.452109] x1 : 0000000000000000 x0 : 0000000000000000 [ 0.452121] Call trace: [ 0.452130] reserve_memblock_reserved_regions+0xd4/0x13c [ 0.452140] do_one_initcall+0x78/0x150 [ 0.452148] kernel_init_freeable+0x198/0x258 [ 0.452159] kernel_init+0x10/0x108 [ 0.452170] ret_from_fork+0x10/0x18 [ 0.452181] ---[ end trace b4b78c443df3a750 ]--- From skimming the patch, it seems this is maybe expected? Or should this warning raise eyebrows? I can't quite figure it out. It seems to trigger on the pstore memory at 0x21f00000-0x21ffffff. /proc/iomem now has: ... 07410000-21efffff : System RAM 11000000-1113cfff : reserved 21f00000-21ffffff : reserved 21f00000-21f1ffff : persistent_ram 21f20000-21f3ffff : persistent_ram 21f40000-21f5ffff : persistent_ram 21f60000-21f7ffff : persistent_ram 21f80000-21f9ffff : persistent_ram 21fa0000-21fbffff : persistent_ram 21fc0000-21fdffff : persistent_ram 21fe0000-21ffffff : persistent_ram 22000000-34ffffff : System RAM ... Where previously it had: ... 07410000-21efffff : System RAM 21f00000-21f1ffff : persistent_ram 21f20000-21f3ffff : persistent_ram 21f40000-21f5ffff : persistent_ram 21f60000-21f7ffff : persistent_ram 21f80000-21f9ffff : persistent_ram 21fa0000-21fbffff : persistent_ram 21fc0000-21fdffff : persistent_ram 21fe0000-21ffffff : persistent_ram 22000000-34ffffff : System RAM ... thanks -john
Hi John, On Mon, Aug 20, 2018 at 09:39:01PM -0700, John Stultz wrote: > On Sun, Jul 22, 2018 at 6:57 PM, AKASHI Takahiro > <takahiro.akashi@linaro.org> wrote: > > From: James Morse <james.morse@arm.com> > > > > There has been some confusion around what is necessary to prevent kexec > > overwriting important memory regions. memblock: reserve, or nomap? > > Only memblock nomap regions are reported via /proc/iomem, kexec's > > user-space doesn't know about memblock_reserve()d regions. > > > > Until commit f56ab9a5b73ca ("efi/arm: Don't mark ACPI reclaim memory > > as MEMBLOCK_NOMAP") the ACPI tables were nomap, now they are reserved > > and thus possible for kexec to overwrite with the new kernel or initrd. > > But this was always broken, as the UEFI memory map is also reserved > > and not marked as nomap. > > > > Exporting both nomap and reserved memblock types is a nuisance as > > they live in different memblock structures which we can't walk at > > the same time. > > > > Take a second walk over memblock.reserved and add new 'reserved' > > subnodes for the memblock_reserved() regions that aren't already > > described by the existing code. (e.g. Kernel Code) > > > > We use reserve_region_with_split() to find the gaps in existing named > > regions. This handles the gap between 'kernel code' and 'kernel data' > > which is memblock_reserve()d, but already partially described by > > request_standard_resources(). e.g.: > > | 80000000-dfffffff : System RAM > > | 80080000-80ffffff : Kernel code > > | 81000000-8158ffff : reserved > > | 81590000-8237efff : Kernel data > > | a0000000-dfffffff : Crash kernel > > | e00f0000-f949ffff : System RAM > > > > reserve_region_with_split needs kzalloc() which isn't available when > > request_standard_resources() is called, use an initcall. > > > > Reported-by: Bhupesh Sharma <bhsharma@redhat.com> > > Reported-by: Tyler Baicar <tbaicar@codeaurora.org> > > Suggested-by: Akashi Takahiro <takahiro.akashi@linaro.org> > > Signed-off-by: James Morse <james.morse@arm.com> > > Fixes: d28f6df1305a ("arm64/kexec: Add core kexec support") > > Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > CC: Mark Rutland <mark.rutland@arm.com> > > --- > > arch/arm64/kernel/setup.c | 38 ++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 38 insertions(+) > > > > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c > > index 30ad2f085d1f..5b4fac434c84 100644 > > --- a/arch/arm64/kernel/setup.c > > +++ b/arch/arm64/kernel/setup.c > > @@ -241,6 +241,44 @@ static void __init request_standard_resources(void) > > } > > } > > > > +static int __init reserve_memblock_reserved_regions(void) > > +{ > > + phys_addr_t start, end, roundup_end = 0; > > + struct resource *mem, *res; > > + u64 i; > > + > > + for_each_reserved_mem_region(i, &start, &end) { > > + if (end <= roundup_end) > > + continue; /* done already */ > > + > > + start = __pfn_to_phys(PFN_DOWN(start)); > > + end = __pfn_to_phys(PFN_UP(end)) - 1; > > + roundup_end = end; > > + > > + res = kzalloc(sizeof(*res), GFP_ATOMIC); > > + if (WARN_ON(!res)) > > + return -ENOMEM; > > + res->start = start; > > + res->end = end; > > + res->name = "reserved"; > > + res->flags = IORESOURCE_MEM; > > + > > + mem = request_resource_conflict(&iomem_resource, res); > > + /* > > + * We expected memblock_reserve() regions to conflict with > > + * memory created by request_standard_resources(). > > + */ > > + if (WARN_ON_ONCE(!mem)) > > + continue; > > + kfree(res); > > + > > + reserve_region_with_split(mem, start, end, "reserved"); > > + } > > + > > + return 0; > > +} > > +arch_initcall(reserve_memblock_reserved_regions); > > + > > Since this patch landed, on the HiKey board at bootup I'm seeing: > > [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 > reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.451896] CPU: 1 PID: 1 Comm: swapper/0 Not tainted > 4.18.0-10758-ga534dc3 #709 > [ 0.451903] Hardware name: HiKey Development Board (DT) > [ 0.451913] pstate: 80400005 (Nzcv daif +PAN -UAO) > [ 0.451922] pc : reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.451931] lr : reserve_memblock_reserved_regions+0xcc/0x13c > [ 0.451938] sp : ffffff8008053d30 > [ 0.451945] x29: ffffff8008053d30 x28: ffffff8008ebe650 > [ 0.451957] x27: ffffff8008ead060 x26: ffffff8008e113b0 > [ 0.451969] x25: 0000000000000000 x24: 0000000000488020 > [ 0.451981] x23: 0000000021ffffff x22: ffffff8008e0d860 > [ 0.451993] x21: ffffff8008d74370 x20: ffffff8009019000 > [ 0.452005] x19: ffffffc07507a400 x18: ffffff8009019a48 > [ 0.452017] x17: 0000000000000000 x16: 0000000000000000 > [ 0.452028] x15: ffffff80890e973f x14: 0000000000000006 > [ 0.452040] x13: 0000000000000000 x12: 0000000000000000 > [ 0.452051] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f > [ 0.452063] x9 : 0000000000000000 x8 : ffffffc07507a480 > [ 0.452074] x7 : 0000000000000000 x6 : ffffffc07ffffc30 > [ 0.452086] x5 : 0000000000000000 x4 : 0000000021ffffff > [ 0.452097] x3 : 0000000000000001 x2 : 0000000000000001 > [ 0.452109] x1 : 0000000000000000 x0 : 0000000000000000 > [ 0.452121] Call trace: > [ 0.452130] reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.452140] do_one_initcall+0x78/0x150 > [ 0.452148] kernel_init_freeable+0x198/0x258 > [ 0.452159] kernel_init+0x10/0x108 > [ 0.452170] ret_from_fork+0x10/0x18 > [ 0.452181] ---[ end trace b4b78c443df3a750 ]--- > > From skimming the patch, it seems this is maybe expected? Or should > this warning raise eyebrows? I can't quite figure it out. Yeah, somehow. This is the case where an inserted region has NOMAP attribute, which means that it has no use for system memory, but is yet "memblock_reserved." (doesn't make sense.) > > It seems to trigger on the pstore memory at 0x21f00000-0x21ffffff. > > /proc/iomem now has: > ... > 07410000-21efffff : System RAM > 11000000-1113cfff : reserved > 21f00000-21ffffff : reserved > 21f00000-21f1ffff : persistent_ram > 21f20000-21f3ffff : persistent_ram > 21f40000-21f5ffff : persistent_ram > 21f60000-21f7ffff : persistent_ram > 21f80000-21f9ffff : persistent_ram > 21fa0000-21fbffff : persistent_ram > 21fc0000-21fdffff : persistent_ram > 21fe0000-21ffffff : persistent_ram > 22000000-34ffffff : System RAM > ... Please note that, after my patch set, there can appear a "reserved" entry at the top level, which implies that the whole range is NOMAP'ed. Thanks, -Takahiro AKASHI > > Where previously it had: > ... > 07410000-21efffff : System RAM > 21f00000-21f1ffff : persistent_ram > 21f20000-21f3ffff : persistent_ram > 21f40000-21f5ffff : persistent_ram > 21f60000-21f7ffff : persistent_ram > 21f80000-21f9ffff : persistent_ram > 21fa0000-21fbffff : persistent_ram > 21fc0000-21fdffff : persistent_ram > 21fe0000-21ffffff : persistent_ram > 22000000-34ffffff : System RAM > ... > > > thanks > -john
Hi John, On 08/21/2018 05:39 AM, John Stultz wrote: > On Sun, Jul 22, 2018 at 6:57 PM, AKASHI Takahiro > <takahiro.akashi@linaro.org> wrote: >> From: James Morse <james.morse@arm.com> >> >> There has been some confusion around what is necessary to prevent kexec >> overwriting important memory regions. memblock: reserve, or nomap? >> Only memblock nomap regions are reported via /proc/iomem, kexec's >> user-space doesn't know about memblock_reserve()d regions. >> >> Until commit f56ab9a5b73ca ("efi/arm: Don't mark ACPI reclaim memory >> as MEMBLOCK_NOMAP") the ACPI tables were nomap, now they are reserved >> and thus possible for kexec to overwrite with the new kernel or initrd. >> But this was always broken, as the UEFI memory map is also reserved >> and not marked as nomap. >> >> Exporting both nomap and reserved memblock types is a nuisance as >> they live in different memblock structures which we can't walk at >> the same time. >> >> Take a second walk over memblock.reserved and add new 'reserved' >> subnodes for the memblock_reserved() regions that aren't already >> described by the existing code. (e.g. Kernel Code) >> >> We use reserve_region_with_split() to find the gaps in existing named >> regions. This handles the gap between 'kernel code' and 'kernel data' >> which is memblock_reserve()d, but already partially described by >> request_standard_resources(). e.g.: >> | 80000000-dfffffff : System RAM >> | 80080000-80ffffff : Kernel code >> | 81000000-8158ffff : reserved >> | 81590000-8237efff : Kernel data >> | a0000000-dfffffff : Crash kernel >> | e00f0000-f949ffff : System RAM >> >> reserve_region_with_split needs kzalloc() which isn't available when >> request_standard_resources() is called, use an initcall. >> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c >> index 30ad2f085d1f..5b4fac434c84 100644 >> --- a/arch/arm64/kernel/setup.c >> +++ b/arch/arm64/kernel/setup.c >> @@ -241,6 +241,44 @@ static void __init request_standard_resources(void) >> +static int __init reserve_memblock_reserved_regions(void) >> + for_each_reserved_mem_region(i, &start, &end) { >> + if (end <= roundup_end) >> + continue; /* done already */ >> + >> + start = __pfn_to_phys(PFN_DOWN(start)); >> + end = __pfn_to_phys(PFN_UP(end)) - 1; >> + roundup_end = end; >> + >> + res = kzalloc(sizeof(*res), GFP_ATOMIC); >> + if (WARN_ON(!res)) >> + return -ENOMEM; >> + res->start = start; >> + res->end = end; >> + res->name = "reserved"; >> + res->flags = IORESOURCE_MEM; >> + >> + mem = request_resource_conflict(&iomem_resource, res); >> + /* >> + * We expected memblock_reserve() regions to conflict with >> + * memory created by request_standard_resources(). >> + */ >> + if (WARN_ON_ONCE(!mem)) >> + continue; >> + kfree(res); >> + >> + reserve_region_with_split(mem, start, end, "reserved"); >> + } >> + >> + return 0; >> +} >> +arch_initcall(reserve_memblock_reserved_regions); >> + > > Since this patch landed, on the HiKey board at bootup I'm seeing: > > [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 > reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.451896] CPU: 1 PID: 1 Comm: swapper/0 Not tainted > 4.18.0-10758-ga534dc3 #709 > [ 0.451903] Hardware name: HiKey Development Board (DT) > [ 0.451913] pstate: 80400005 (Nzcv daif +PAN -UAO) > [ 0.451922] pc : reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.451931] lr : reserve_memblock_reserved_regions+0xcc/0x13c > [ 0.451938] sp : ffffff8008053d30 > [ 0.451945] x29: ffffff8008053d30 x28: ffffff8008ebe650 > [ 0.451957] x27: ffffff8008ead060 x26: ffffff8008e113b0 > [ 0.451969] x25: 0000000000000000 x24: 0000000000488020 > [ 0.451981] x23: 0000000021ffffff x22: ffffff8008e0d860 > [ 0.451993] x21: ffffff8008d74370 x20: ffffff8009019000 > [ 0.452005] x19: ffffffc07507a400 x18: ffffff8009019a48 > [ 0.452017] x17: 0000000000000000 x16: 0000000000000000 > [ 0.452028] x15: ffffff80890e973f x14: 0000000000000006 > [ 0.452040] x13: 0000000000000000 x12: 0000000000000000 > [ 0.452051] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f > [ 0.452063] x9 : 0000000000000000 x8 : ffffffc07507a480 > [ 0.452074] x7 : 0000000000000000 x6 : ffffffc07ffffc30 > [ 0.452086] x5 : 0000000000000000 x4 : 0000000021ffffff > [ 0.452097] x3 : 0000000000000001 x2 : 0000000000000001 > [ 0.452109] x1 : 0000000000000000 x0 : 0000000000000000 > [ 0.452121] Call trace: > [ 0.452130] reserve_memblock_reserved_regions+0xd4/0x13c > [ 0.452140] do_one_initcall+0x78/0x150 > [ 0.452148] kernel_init_freeable+0x198/0x258 > [ 0.452159] kernel_init+0x10/0x108 > [ 0.452170] ret_from_fork+0x10/0x18 > [ 0.452181] ---[ end trace b4b78c443df3a750 ]--- > > From skimming the patch, it seems this is maybe expected? Or should > this warning raise eyebrows? I can't quite figure it out. Ugh, sorry for the noise! This is warning that there is something wrong with our assumptions about what types of memory exist. > It seems to trigger on the pstore memory at 0x21f00000-0x21ffffff. ... pmem ... > > /proc/iomem now has: > ... > 07410000-21efffff : System RAM > 11000000-1113cfff : reserved > 21f00000-21ffffff : reserved ^ This entry is what triggered the warning. It expects that meblock_reserved() memory is also described as memory. (memblock keeps them as separate lists, so its possible to reserve memory that doesn't exist... which it looks like your system is doing) If this region was described as memory, request_standard_resources() would have put down a "System RAM" resource to cover it. This code is trying to add a "reserved" underneath that, to discover the top level doesn't exist. The reserved entry gets left in place as this region is described as reserved... Akashi and I figured this would only happen if a region is described as nomap-memory and memblock_reserved() at the same time, which we don't think is valid, hence the warning. This avoided walking each reserved region, to work out which parts of it were memory, nomap-memory (and now, not memory at all!) > 21f00000-21f1ffff : persistent_ram > 21f20000-21f3ffff : persistent_ram > 21f40000-21f5ffff : persistent_ram > 21f60000-21f7ffff : persistent_ram > 21f80000-21f9ffff : persistent_ram > 21fa0000-21fbffff : persistent_ram > 21fc0000-21fdffff : persistent_ram > 21fe0000-21ffffff : persistent_ram > 22000000-34ffffff : System RAM > ... > > Where previously it had: > ... > 07410000-21efffff : System RAM > 21f00000-21f1ffff : persistent_ram > 21f20000-21f3ffff : persistent_ram > 21f40000-21f5ffff : persistent_ram > 21f60000-21f7ffff : persistent_ram > 21f80000-21f9ffff : persistent_ram > 21fa0000-21fbffff : persistent_ram > 21fc0000-21fdffff : persistent_ram > 21fe0000-21ffffff : persistent_ram > 22000000-34ffffff : System RAM So, this is a memblock_reserved() range that isn't actually memory. This happens because your DT has carved these regions out of the memory node, but added a named 'reserved-memory' region for them, just in case? I'm not sure what it means if 'reserved-memory' is not also described as memory.... You do need the carve-out, otherwise this gets covered by the linear map, and when you throw in that 'unbuffered' property you get both a cacheable and uncacheable mapping of the same page. ... and if you have the carve-out, you don't need the reserved-memory as this is effectively a device which the driver knows the memory-attributes for... I think the problem here is making 'persistent memory' e.g. byte-addressable flash and 'reserved memory' (RAM) mean the same thing. Something like [0] should mute the warning, but this assumes your memblock_reserved() region didn't get merged with another reserved region that really is memory, so just doing this makes it more fragile... I will see if I can come up with something better. Thanks, James [0] not even build tested ----------------------%<---------------------- diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 5b4fac4..c64541b 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -266,10 +266,15 @@ static int __init reserve_memblock_reserved_regions(void) mem = request_resource_conflict(&iomem_resource, res); /* * We expected memblock_reserve() regions to conflict with - * memory created by request_standard_resources(). + * memory created by request_standard_resources(). This doesn't + * happen if we found a region that is memblock_reserved(), but + * not actually memory. */ - if (WARN_ON_ONCE(!mem)) + if (!mem) { + remove_resource(res); + kfree(res); continue; + } kfree(res); reserve_region_with_split(mem, start, end, "reserved"); ----------------------%<----------------------
On 08/21/2018 11:22 AM, James Morse wrote: > On 08/21/2018 05:39 AM, John Stultz wrote: >> On Sun, Jul 22, 2018 at 6:57 PM, AKASHI Takahiro >> <takahiro.akashi@linaro.org> wrote: >>> From: James Morse <james.morse@arm.com> >>> >>> There has been some confusion around what is necessary to prevent kexec >>> overwriting important memory regions. memblock: reserve, or nomap? >>> Only memblock nomap regions are reported via /proc/iomem, kexec's >>> user-space doesn't know about memblock_reserve()d regions. >>> >>> Until commit f56ab9a5b73ca ("efi/arm: Don't mark ACPI reclaim memory >>> as MEMBLOCK_NOMAP") the ACPI tables were nomap, now they are reserved >>> and thus possible for kexec to overwrite with the new kernel or initrd. >>> But this was always broken, as the UEFI memory map is also reserved >>> and not marked as nomap. >>> >>> Exporting both nomap and reserved memblock types is a nuisance as >>> they live in different memblock structures which we can't walk at >>> the same time. >>> >>> Take a second walk over memblock.reserved and add new 'reserved' >>> subnodes for the memblock_reserved() regions that aren't already >>> described by the existing code. (e.g. Kernel Code) >>> >>> We use reserve_region_with_split() to find the gaps in existing named >>> regions. This handles the gap between 'kernel code' and 'kernel data' >>> which is memblock_reserve()d, but already partially described by >>> request_standard_resources(). e.g.: >>> | 80000000-dfffffff : System RAM >>> | 80080000-80ffffff : Kernel code >>> | 81000000-8158ffff : reserved >>> | 81590000-8237efff : Kernel data >>> | a0000000-dfffffff : Crash kernel >>> | e00f0000-f949ffff : System RAM >>> >>> reserve_region_with_split needs kzalloc() which isn't available when >>> request_standard_resources() is called, use an initcall. > >>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c >>> index 30ad2f085d1f..5b4fac434c84 100644 >>> --- a/arch/arm64/kernel/setup.c >>> +++ b/arch/arm64/kernel/setup.c >>> @@ -241,6 +241,44 @@ static void __init request_standard_resources(void) > >>> +static int __init reserve_memblock_reserved_regions(void) > >>> + for_each_reserved_mem_region(i, &start, &end) { >>> + if (end <= roundup_end) >>> + continue; /* done already */ >>> + >>> + start = __pfn_to_phys(PFN_DOWN(start)); >>> + end = __pfn_to_phys(PFN_UP(end)) - 1; >>> + roundup_end = end; >>> + >>> + res = kzalloc(sizeof(*res), GFP_ATOMIC); >>> + if (WARN_ON(!res)) >>> + return -ENOMEM; >>> + res->start = start; >>> + res->end = end; >>> + res->name = "reserved"; >>> + res->flags = IORESOURCE_MEM; >>> + >>> + mem = request_resource_conflict(&iomem_resource, res); >>> + /* >>> + * We expected memblock_reserve() regions to conflict with >>> + * memory created by request_standard_resources(). >>> + */ >>> + if (WARN_ON_ONCE(!mem)) >> Since this patch landed, on the HiKey board at bootup I'm seeing: >> >> [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 >> reserve_memblock_reserved_regions+0xd4/0x13c >> From skimming the patch, it seems this is maybe expected? Or should >> this warning raise eyebrows? I can't quite figure it out. > > Ugh, sorry for the noise! This is warning that there is something wrong > with our assumptions about what types of memory exist. > > >> It seems to trigger on the pstore memory at 0x21f00000-0x21ffffff. > > ... pmem ... > So, this is a memblock_reserved() range that isn't actually memory. > > This happens because your DT has carved these regions out of the memory > node, but added a named 'reserved-memory' region for them, just in case? > I'm not sure what it means if 'reserved-memory' is not also described as > memory.... > > You do need the carve-out, otherwise this gets covered by the linear > map, and when you throw in that 'unbuffered' property you get both a > cacheable and uncacheable mapping of the same page. Hmm, looks like its (even) more complicated than I thought, of_reserved_mem.c's definition of 'nomap' is memblock_remove(), not memblock_mark_nomap(). This might be more common to all users of DTs memreserve. Thanks, James
On Tue, Aug 21, 2018 at 3:22 AM, James Morse <james.morse@arm.com> wrote: > On 08/21/2018 05:39 AM, John Stultz wrote: >> >> Since this patch landed, on the HiKey board at bootup I'm seeing: >> >> [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 >> reserve_memblock_reserved_regions+0xd4/0x13c ... >> From skimming the patch, it seems this is maybe expected? Or should >> this warning raise eyebrows? I can't quite figure it out. > > Ugh, sorry for the noise! This is warning that there is something wrong > with our assumptions about what types of memory exist. > > >> It seems to trigger on the pstore memory at 0x21f00000-0x21ffffff. > > > ... pmem ... > >> >> /proc/iomem now has: >> ... >> 07410000-21efffff : System RAM >> 11000000-1113cfff : reserved > > >> 21f00000-21ffffff : reserved > > > ^ This entry is what triggered the warning. > > It expects that meblock_reserved() memory is also described as memory. > (memblock keeps them as separate lists, so its possible to reserve > memory that doesn't exist... which it looks like your system is doing) So yea, I suspect the hikey dts isn't quite right here then. I've always thought how it setup the memory was a bit strange: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts#n30 So from your mail, I suspect the hole in the memory map for the pstore buffer isn't correct, and we should rework that. I'll give that a shot here and make sure pstore still works properly. thanks -john
Hi John, On 21/08/18 20:38, John Stultz wrote: > On Tue, Aug 21, 2018 at 3:22 AM, James Morse <james.morse@arm.com> wrote: >> On 08/21/2018 05:39 AM, John Stultz wrote: >>> >>> Since this patch landed, on the HiKey board at bootup I'm seeing: >>> >>> [ 0.451884] WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/setup.c:271 >>> reserve_memblock_reserved_regions+0xd4/0x13c > ... >>> From skimming the patch, it seems this is maybe expected? Or should >>> this warning raise eyebrows? I can't quite figure it out. >> >>> /proc/iomem now has: >>> ... >>> 07410000-21efffff : System RAM >>> 11000000-1113cfff : reserved >> >> >>> 21f00000-21ffffff : reserved >> >> >> ^ This entry is what triggered the warning. >> >> It expects that meblock_reserved() memory is also described as memory. >> (memblock keeps them as separate lists, so its possible to reserve >> memory that doesn't exist... which it looks like your system is doing) > > So yea, I suspect the hikey dts isn't quite right here then. The DT mem-reserve code goes and memblock_removes() some regions, instead of marking them nomap. Given memblock has a for_each_resv_unavail_range() that explicitly walks reserved && !memory, it looks like this is expected, and its just me thinking this is strange. I will come up with a version of this patch that walks the 'System RAM' resources that were created during boot, and adds the memblock_reserved() regions to them, which should stop this happening. Thanks, James
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 30ad2f085d1f..5b4fac434c84 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -241,6 +241,44 @@ static void __init request_standard_resources(void) } } +static int __init reserve_memblock_reserved_regions(void) +{ + phys_addr_t start, end, roundup_end = 0; + struct resource *mem, *res; + u64 i; + + for_each_reserved_mem_region(i, &start, &end) { + if (end <= roundup_end) + continue; /* done already */ + + start = __pfn_to_phys(PFN_DOWN(start)); + end = __pfn_to_phys(PFN_UP(end)) - 1; + roundup_end = end; + + res = kzalloc(sizeof(*res), GFP_ATOMIC); + if (WARN_ON(!res)) + return -ENOMEM; + res->start = start; + res->end = end; + res->name = "reserved"; + res->flags = IORESOURCE_MEM; + + mem = request_resource_conflict(&iomem_resource, res); + /* + * We expected memblock_reserve() regions to conflict with + * memory created by request_standard_resources(). + */ + if (WARN_ON_ONCE(!mem)) + continue; + kfree(res); + + reserve_region_with_split(mem, start, end, "reserved"); + } + + return 0; +} +arch_initcall(reserve_memblock_reserved_regions); + u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID }; void __init setup_arch(char **cmdline_p)