253 lines
8.4 KiB
Diff
253 lines
8.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Wed, 15 Apr 2020 23:28:29 +1000
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Subject: [PATCH] ieee1275: claim more memory
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On powerpc-ieee1275, we are running out of memory trying to verify
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anything. This is because:
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- we have to load an entire file into memory to verify it. This is
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extremely difficult to change with appended signatures.
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- We only have 32MB of heap.
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- Distro kernels are now often around 30MB.
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So we want to claim more memory from OpenFirmware for our heap.
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There are some complications:
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- The grub mm code isn't the only thing that will make claims on
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memory from OpenFirmware:
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* PFW/SLOF will have claimed some for their own use.
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* The ieee1275 loader will try to find other bits of memory that we
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haven't claimed to place the kernel and initrd when we go to boot.
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* Once we load Linux, it will also try to claim memory. It claims
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memory without any reference to /memory/available, it just starts
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at min(top of RMO, 768MB) and works down. So we need to avoid this
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area. See arch/powerpc/kernel/prom_init.c as of v5.11.
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- The smallest amount of memory a ppc64 KVM guest can have is 256MB.
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It doesn't work with distro kernels but can work with custom kernels.
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We should maintain support for that. (ppc32 can boot with even less,
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and we shouldn't break that either.)
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- Even if a VM has more memory, the memory OpenFirmware makes available
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as Real Memory Area can be restricted. A freshly created LPAR on a
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PowerVM machine is likely to have only 256MB available to OpenFirmware
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even if it has many gigabytes of memory allocated.
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EFI systems will attempt to allocate 1/4th of the available memory,
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clamped to between 1M and 1600M. That seems like a good sort of
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approach, we just need to figure out if 1/4 is the right fraction
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for us.
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We don't know in advance how big the kernel and initrd are going to be,
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which makes figuring out how much memory we can take a bit tricky.
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To figure out how much memory we should leave unused, I looked at:
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- an Ubuntu 20.04.1 ppc64le pseries KVM guest:
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vmlinux: ~30MB
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initrd: ~50MB
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- a RHEL8.2 ppc64le pseries KVM guest:
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vmlinux: ~30MB
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initrd: ~30MB
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Ubuntu VMs struggle to boot with just 256MB under SLOF.
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RHEL likewise has a higher minimum supported memory figure.
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So lets first consider a distro kernel and 512MB of addressible memory.
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(This is the default case for anything booting under PFW.) Say we lose
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131MB to PFW (based on some tests). This leaves us 381MB. 1/4 of 381MB
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is ~95MB. That should be enough to verify a 30MB vmlinux and should
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leave plenty of space to load Linux and the initrd.
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If we consider 256MB of RMA under PFW, we have just 125MB remaining. 1/4
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of that is a smidge under 32MB, which gives us very poor odds of verifying
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a distro-sized kernel. However, if we need 80MB just to put the kernel
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and initrd in memory, we can't claim any more than 45MB anyway. So 1/4
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will do. We'll come back to this later.
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grub is always built as a 32-bit binary, even if it's loading a ppc64
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kernel. So we can't address memory beyond 4GB. This gives a natural cap
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of 1GB for powerpc-ieee1275.
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Also apply this 1/4 approach to i386-ieee1275, but keep the 32MB cap.
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make check still works for both i386 and powerpc and I've booted
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powerpc grub with this change under SLOF and PFW.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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---
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grub-core/kern/ieee1275/init.c | 81 +++++++++++++++++++++++++++++++++---------
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docs/grub-dev.texi | 6 ++--
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2 files changed, 69 insertions(+), 18 deletions(-)
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diff --git a/grub-core/kern/ieee1275/init.c b/grub-core/kern/ieee1275/init.c
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index 0dcd114ce54..c61d91a0285 100644
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--- a/grub-core/kern/ieee1275/init.c
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+++ b/grub-core/kern/ieee1275/init.c
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@@ -46,11 +46,12 @@
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#endif
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#include <grub/lockdown.h>
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-/* The maximum heap size we're going to claim */
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+/* The maximum heap size we're going to claim. Not used by sparc.
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+ We allocate 1/4 of the available memory under 4G, up to this limit. */
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#ifdef __i386__
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#define HEAP_MAX_SIZE (unsigned long) (64 * 1024 * 1024)
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-#else
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-#define HEAP_MAX_SIZE (unsigned long) (32 * 1024 * 1024)
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+#else // __powerpc__
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+#define HEAP_MAX_SIZE (unsigned long) (1 * 1024 * 1024 * 1024)
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#endif
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extern char _end[];
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@@ -147,16 +148,45 @@ grub_claim_heap (void)
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+ GRUB_KERNEL_MACHINE_STACK_SIZE), 0x200000);
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}
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#else
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-/* Helper for grub_claim_heap. */
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+/* Helper for grub_claim_heap on powerpc. */
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+static int
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+heap_size (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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+ void *data)
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+{
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+ grub_uint32_t total = *(grub_uint32_t *)data;
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+
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+ if (type != GRUB_MEMORY_AVAILABLE)
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+ return 0;
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+
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+ /* Do not consider memory beyond 4GB */
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+ if (addr > 0xffffffffUL)
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+ return 0;
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+
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+ if (addr + len > 0xffffffffUL)
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+ len = 0xffffffffUL - addr;
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+
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+ total += len;
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+ *(grub_uint32_t *)data = total;
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+
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+ return 0;
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+}
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+
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static int
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heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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void *data)
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{
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- unsigned long *total = data;
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+ grub_uint32_t total = *(grub_uint32_t *)data;
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if (type != GRUB_MEMORY_AVAILABLE)
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return 0;
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+ /* Do not consider memory beyond 4GB */
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+ if (addr > 0xffffffffUL)
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+ return 0;
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+
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+ if (addr + len > 0xffffffffUL)
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+ len = 0xffffffffUL - addr;
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+
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if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_NO_PRE1_5M_CLAIM))
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{
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if (addr + len <= 0x180000)
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@@ -170,10 +200,6 @@ heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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}
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len -= 1; /* Required for some firmware. */
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- /* Never exceed HEAP_MAX_SIZE */
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- if (*total + len > HEAP_MAX_SIZE)
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- len = HEAP_MAX_SIZE - *total;
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-
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/* In theory, firmware should already prevent this from happening by not
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listing our own image in /memory/available. The check below is intended
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as a safeguard in case that doesn't happen. However, it doesn't protect
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@@ -185,6 +211,18 @@ heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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len = 0;
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}
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+ /* If this block contains 0x30000000 (768MB), do not claim below that.
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+ Linux likes to claim memory at min(RMO top, 768MB) and works down
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+ without reference to /memory/available. */
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+ if ((addr < 0x30000000) && ((addr + len) > 0x30000000))
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+ {
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+ len = len - (0x30000000 - addr);
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+ addr = 0x30000000;
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+ }
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+
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+ if (len > total)
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+ len = total;
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+
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if (len)
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{
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grub_err_t err;
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@@ -193,10 +231,12 @@ heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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if (err)
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return err;
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grub_mm_init_region ((void *) (grub_addr_t) addr, len);
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+ total -= len;
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}
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- *total += len;
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- if (*total >= HEAP_MAX_SIZE)
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+ *(grub_uint32_t *)data = total;
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+
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+ if (total == 0)
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return 1;
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return 0;
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@@ -205,13 +245,22 @@ heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
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static void
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grub_claim_heap (void)
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{
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- unsigned long total = 0;
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+ grub_uint32_t total = 0;
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if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_FORCE_CLAIM))
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- heap_init (GRUB_IEEE1275_STATIC_HEAP_START, GRUB_IEEE1275_STATIC_HEAP_LEN,
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- 1, &total);
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- else
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- grub_machine_mmap_iterate (heap_init, &total);
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+ {
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+ heap_init (GRUB_IEEE1275_STATIC_HEAP_START, GRUB_IEEE1275_STATIC_HEAP_LEN,
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+ 1, &total);
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+ return;
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+ }
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+
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+ grub_machine_mmap_iterate (heap_size, &total);
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+
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+ total = total / 4;
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+ if (total > HEAP_MAX_SIZE)
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+ total = HEAP_MAX_SIZE;
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+
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+ grub_machine_mmap_iterate (heap_init, &total);
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}
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#endif
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diff --git a/docs/grub-dev.texi b/docs/grub-dev.texi
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index a55af53fd45..008bd7a3c34 100644
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--- a/docs/grub-dev.texi
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+++ b/docs/grub-dev.texi
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@@ -1047,7 +1047,9 @@ space is limited to 4GiB. GRUB allocates pages from EFI for its heap, at most
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1.6 GiB.
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On i386-ieee1275 and powerpc-ieee1275 GRUB uses same stack as IEEE1275.
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-It allocates at most 32MiB for its heap.
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+
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+On i386-ieee1275, GRUB allocates at most 32MiB for its heap. On
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+powerpc-ieee1275, GRUB allocates up to 1GiB.
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On sparc64-ieee1275 stack is 256KiB and heap is 2MiB.
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@@ -1075,7 +1077,7 @@ In short:
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@item i386-qemu @tab 60 KiB @tab < 4 GiB
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@item *-efi @tab ? @tab < 1.6 GiB
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@item i386-ieee1275 @tab ? @tab < 32 MiB
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-@item powerpc-ieee1275 @tab ? @tab < 32 MiB
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+@item powerpc-ieee1275 @tab ? @tab < 1 GiB
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@item sparc64-ieee1275 @tab 256KiB @tab 2 MiB
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@item arm-uboot @tab 256KiB @tab 2 MiB
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@item mips(el)-qemu_mips @tab 2MiB @tab 253 MiB
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