Re: [PATCH 0/2] ESRT fixes for relocatable kexec'd kernel

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

Tyler, Jeffrey,

On Fri, Mar 02, 2018 at 08:27:11AM -0500, Tyler Baicar wrote:
> On 3/2/2018 12:53 AM, AKASHI Takahiro wrote:
> >Tyler, Jeffrey,
> >
> >[Note: This issue takes place in kexec, not kdump. So to be precise,
> >it is not the same phenomenon as what I addressed in [1],[2]:
> >   [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-February/557254.html
> >   [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-January/553098.html
> >]
> >
> >On Thu, Mar 01, 2018 at 12:56:38PM -0500, Tyler Baicar wrote:
> >>Hello,
> >>
> >>On 2/28/2018 9:50 PM, AKASHI Takahiro wrote:
> >>>Hi,
> >>>
> >>>On Wed, Feb 28, 2018 at 08:39:42AM -0700, Jeffrey Hugo wrote:
> >>>>On 2/27/2018 11:19 PM, AKASHI Takahiro wrote:
> >>>>>Tyler,
> >>>>>
> >>>>># I missed catching your patch as its subject doesn't contain arm64.
> >>>>>
> >>>>>On Fri, Feb 23, 2018 at 12:42:31PM -0700, Tyler Baicar wrote:
> >>>>>>Currently on arm64 ESRT memory does not appear to be properly blocked off.
> >>>>>>Upon successful initialization, ESRT prints out the memory region that it
> >>>>>>exists in like:
> >>>>>>
> >>>>>>esrt: Reserving ESRT space from 0x000000000a4c1c18 to 0x000000000a4c1cf0.
> >>>>>>
> >>>>>>But then by dumping /proc/iomem this region appears as part of System RAM
> >>>>>>rather than being reserved:
> >>>>>>
> >>>>>>08f10000-0deeffff : System RAM
> >>>>>>
> >>>>>>This causes issues when trying to kexec if the kernel is relocatable. When
> >>>>>>kexec tries to execute, this memory can be selected to relocate the kernel to
> >>>>>>which then overwrites all the ESRT information. Then when the kexec'd kernel
> >>>>>>tries to initialize ESRT, it doesn't recognize the ESRT version number and
> >>>>>>just returns from efi_esrt_init().
> >>>>>I'm not sure what is the root cause of your problem.
> >>>>>Do you have good confidence that the kernel (2nd kernel image in this case?)
> >>>>>really overwrite ESRT region?
> >>>>According to my debug, yes.
> >>>>Using JTAG, I was able to determine that the ESRT memory region was getting
> >>>>overwritten by the secondary kernel in
> >>>>kernel/arch/arm64/kernel/relocate_kernel.S - specifically the "copy_page"
> >>>>line of arm64_relocate_new_kernel()
> >>>>
> >>>>>To my best knowledge, kexec is carefully designed not to do such a thing
> >>>>>as it allocates a temporary buffer for kernel image and copies it to the
> >>>>>final destination at the very end of the 1st kernel.
> >>>>>
> >>>>>My guess is that kexec, or rather kexec-tools, tries to load the kernel image
> >>>>>at 0x8f80000 (or 0x9080000?, not sure) in your case. It may or may not be
> >>>>>overlapped with ESRT.
> >>>>>(Try "-d" option when executing kexec command for confirmation.)
> >>>>With -d, I see
> >>>>
> >>>>get_memory_ranges_iomem_cb: 0000000009611000 - 000000000e5fffff : System RAM
> >>>>
> >>>>That overlaps the ESRT reservation -
> >>>>[ 0.000000] esrt: Reserving ESRT space from 0x000000000b708718 to
> >>>>0x000000000b7087f0
> >>>>
> >>>>>Are you using initrd with kexec?
> >>>>Yes
> >>>To make the things clear, can you show me, if possible, the followings:
> >>I have attached all of these:
> >Many thanks.
> >According to the data, ESRT was overwritten by initrd, not the kernel image.
> >It doesn't matter to you though :)
> >
> >The solution would be, as Ard suggested, that more information be
> >added to /proc/iomem.
> >I'm going to fix the issue as quickly as possible.
> Great, thank you!! Please add us to the fix and we will gladly test it out.

I have created a workaround patch, attached below, as a kind of PoC.
Can you give it a go, please?
You need another patch for kexec-tools, too. See
https:/git.linaro.org/people/takahiro.akashi/kexecl-tools.git arm64/resv_mem

With this patch, extra entries for firmware-reserved memory resources,
which means any regions that are already reserved before arm64_memblock_init(),
or specifically efi/acpi tables in this case, are added to /proc/iomem.

 $ cat /proc/iomem (on my qemu+edk2 execution)
        ...
        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
          59a7b118-59a7b667 : reserved
        5be40000-5becffff : reserved
        5bed0000-5bedffff : System RAM
          5bee0000-5bffffff : reserved
        5c000000-5fffffff : System RAM
          5ec00000-5edfffff : reserved
        8000000000-ffffffffff : PCI Bus 0000:00
          8000000000-8000003fff : 0000:00:01.0
            8000000000-8000003fff : virtio-pci-modern

While all the entries are currently marked as just "reserved," we'd better
give them more specific names for general/extensive use.
(Then it will require modifying respective fw/drivers.)

Kexec-tools will allocate spaces for kernel, initrd and dtb so that
they will not be overlapped with "reserved" memory.

As I haven't run extensive tests, please let me know if you find
any problems.

Thanks,
-Takahiro AKASHI

> 
> Thanks,
> Tyler
> 
> -- 
> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project.
> 
===8<===
>From 57d93b89d16b967c913f3949601a5559ddf4aa57 Mon Sep 17 00:00:00 2001
From: AKASHI Takahiro <takahiro.akashi@linaro.org>
Date: Fri, 2 Mar 2018 16:39:18 +0900
Subject: [PATCH] arm64: kexec: set asdie firmware-reserved memory regions

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
 arch/arm64/kernel/setup.c | 24 ++++++++++++++++++++----
 arch/arm64/mm/init.c      | 21 +++++++++++++++++++++
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 30ad2f085d1f..997f07e86243 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -87,6 +87,9 @@ static struct resource mem_res[] = {
 #define kernel_code mem_res[0]
 #define kernel_data mem_res[1]
 
+/* TODO: Firmware-reserved memory resources */
+extern struct memblock_type fw_mem;
+
 /*
  * The recorded values of x0 .. x3 upon kernel entry.
  */
@@ -206,7 +209,20 @@ static void __init request_standard_resources(void)
 {
 	struct memblock_region *region;
 	struct resource *res;
+	int i;
+
+	/* add firmware-reserved memory first */
+	for (i = 1; i < fw_mem.cnt; i++) {
+		res = alloc_bootmem_low(sizeof(*res));
+		res->name  = "reserved";
+		res->flags = IORESOURCE_MEM;
+		res->start = fw_mem.regions[i].base;
+		res->end = fw_mem.regions[i].base + fw_mem.regions[i].size - 1;
 
+		request_resource(&iomem_resource, res);
+	}
+
+	/* add standard resources */
 	kernel_code.start   = __pa_symbol(_text);
 	kernel_code.end     = __pa_symbol(__init_begin - 1);
 	kernel_data.start   = __pa_symbol(_sdata);
@@ -224,19 +240,19 @@ static void __init request_standard_resources(void)
 		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
 		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
 
-		request_resource(&iomem_resource, res);
+		insert_resource(&iomem_resource, res);
 
 		if (kernel_code.start >= res->start &&
 		    kernel_code.end <= res->end)
-			request_resource(res, &kernel_code);
+			insert_resource(res, &kernel_code);
 		if (kernel_data.start >= res->start &&
 		    kernel_data.end <= res->end)
-			request_resource(res, &kernel_data);
+			insert_resource(res, &kernel_data);
 #ifdef CONFIG_KEXEC_CORE
 		/* Userspace will find "Crash kernel" region in /proc/iomem. */
 		if (crashk_res.end && crashk_res.start >= res->start &&
 		    crashk_res.end <= res->end)
-			request_resource(res, &crashk_res);
+			insert_resource(res, &crashk_res);
 #endif
 	}
 }
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 9f3c47acf8ff..b6f86a7bbfb7 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -62,6 +62,14 @@
 s64 memstart_addr __ro_after_init = -1;
 phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
+static struct memblock_region fw_mem_regions[INIT_MEMBLOCK_REGIONS];
+struct memblock_type fw_mem = {
+	.regions	= fw_mem_regions,
+	.cnt		= 1,    /* empty dummy entry */
+	.max		= INIT_MEMBLOCK_REGIONS,
+	.name		= "firmware-reserved memory",
+};
+
 #ifdef CONFIG_BLK_DEV_INITRD
 static int __init early_initrd(char *p)
 {
@@ -362,6 +370,19 @@ static void __init fdt_enforce_memory_region(void)
 void __init arm64_memblock_init(void)
 {
 	const s64 linear_region_size = -(s64)PAGE_OFFSET;
+	struct memblock_region *region;
+
+	/*
+	 * Export firmware-reserved memory regions
+	 * TODO: via more generic interface
+	 */
+	for_each_memblock(reserved, region) {
+		if (WARN_ON(fw_mem.cnt >= fw_mem.max))
+			break;
+		fw_mem.regions[fw_mem.cnt].base = region->base;
+		fw_mem.regions[fw_mem.cnt].size = region->size;
+		fw_mem.cnt++;
+	}
 
 	/* Handle linux,usable-memory-range property */
 	fdt_enforce_memory_region();
-- 
2.16.2