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[Qemu-devel] [PULL 48/49] i386: allow to load initrd below 4 GB for rece
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 48/49] i386: allow to load initrd below 4 GB for recent linux |
Date: |
Mon, 21 Jan 2019 19:06:19 +0100 |
From: Li Zhijian <address@hidden>
Since linux commit: cf8fa920cb42 ("i386: handle an initrd in highmem (version
2)")
linux has supported initrd up to 4 GB, but the header field
ramdisk_max is still set to 2 GB to avoid "possible bootloader bugs".
When use '-kernel vmlinux -initrd initrd.cgz' to launch a VM,
the firmware(it could be linuxboot_dma.bin) helps to read initrd
contents into guest memory(below ramdisk_max) and jump to kernel.
that's similar with what bootloader does, like grub.
In addition, initrd_max is uint32_t simply because QEMU doesn't support
the 64-bit boot protocol (specifically the ext_ramdisk_image field).
Therefore here just limit initrd_max to UINT32_MAX simply as well to
allow initrd to be loaded below 4 GB.
NOTE: it's possible that linux protocol within [0x208, 0x20c]
supports up to 4 GB initrd as well.
CC: Paolo Bonzini <address@hidden>
CC: Richard Henderson <address@hidden>
CC: Eduardo Habkost <address@hidden>
CC: "Michael S. Tsirkin" <address@hidden>
CC: Marcel Apfelbaum <address@hidden>
Signed-off-by: Li Zhijian <address@hidden>
Reviewed-by: Eduardo Habkost <address@hidden>
Reviewed-by: Stefano Garzarella <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/i386/pc.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 90e684d..3d66f81 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1289,7 +1289,26 @@ static void load_linux(PCMachineState *pcms,
#endif
/* highest address for loading the initrd */
- if (protocol >= 0x203) {
+ if (protocol >= 0x20c &&
+ lduw_p(header+0x236) & XLF_CAN_BE_LOADED_ABOVE_4G) {
+ /*
+ * Linux has supported initrd up to 4 GB for a very long time (2007,
+ * long before XLF_CAN_BE_LOADED_ABOVE_4G which was added in 2013),
+ * though it only sets initrd_max to 2 GB to "work around bootloader
+ * bugs". Luckily, QEMU firmware(which does something like bootloader)
+ * has supported this.
+ *
+ * It's believed that if XLF_CAN_BE_LOADED_ABOVE_4G is set, initrd can
+ * be loaded into any address.
+ *
+ * In addition, initrd_max is uint32_t simply because QEMU doesn't
+ * support the 64-bit boot protocol (specifically the ext_ramdisk_image
+ * field).
+ *
+ * Therefore here just limit initrd_max to UINT32_MAX simply as well.
+ */
+ initrd_max = UINT32_MAX;
+ } else if (protocol >= 0x203) {
initrd_max = ldl_p(header+0x22c);
} else {
initrd_max = 0x37ffffff;
--
1.8.3.1
- [Qemu-devel] [PULL 34/49] Revert "i386: Add CPUID bit for PCONFIG", (continued)
- [Qemu-devel] [PULL 34/49] Revert "i386: Add CPUID bit for PCONFIG", Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 35/49] target-i386: hvf: remove MPX support, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 37/49] contrib/elf2dmp: use GLib in ELF processing, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 02/49] include: update Linux headers to 4.21-rc1/5.0-rc1, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 29/49] linuxboot_dma: move common functions in a new header, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 33/49] i386: remove the 'INTEL_PT' CPUID bit from named CPU models, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 42/49] monitor: do not use QTAILQ_FOREACH_SAFE across critical sections, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 43/49] crypto: finish removing TABs, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 44/49] ui: vnc: finish removing TABs, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 47/49] i386: import & use bootparam.h, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 48/49] i386: allow to load initrd below 4 GB for recent linux,
Paolo Bonzini <=
- [Qemu-devel] [PULL 46/49] hw/core/loader.c: Read as long as possible in load_image_size(), Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 45/49] unify len and addr type for memory/address APIs, Paolo Bonzini, 2019/01/21
- [Qemu-devel] [PULL 49/49] docker: disable Xen on CentOS 7, Paolo Bonzini, 2019/01/21
- Re: [Qemu-devel] [PULL 00/49] Misc patches for 2019-01-21, Peter Maydell, 2019/01/22