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[Qemu-devel] [PULL 24/28] linuxboot: compute initrd loading address
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 24/28] linuxboot: compute initrd loading address |
Date: |
Thu, 9 Oct 2014 12:17:31 +0200 |
Even though hw/i386/pc.c tries to compute a valid loading address for the
initrd, close to the top of RAM, this does not take into account other
data that is malloced into that memory by SeaBIOS.
Luckily we can easily look at the memory map to find out how much memory is
used up there. This patch places the initrd in the first four gigabytes,
below the first hole (as returned by INT 15h, AX=e801h).
Without this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x0710a000-0x07fd7fff]
With this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x07112000-0x07fdffff]
So linuxboot is able to use the 64k that were added as padding for
QEMU <= 2.1.
Acked-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
pc-bios/linuxboot.bin | Bin 1024 -> 1024 bytes
pc-bios/optionrom/linuxboot.S | 47 ++++++++++++++++++++++++++++++++++++++----
pc-bios/optionrom/optionrom.h | 21 ++++++++++++++++---
3 files changed, 61 insertions(+), 7 deletions(-)
diff --git a/pc-bios/linuxboot.bin b/pc-bios/linuxboot.bin
index
e7c36694f997c3c34f7f4af3c2923bd2ef6094e7..130103fb739228a6869aaf1b174b9d20c13378fc
100644
GIT binary patch
delta 168
zcmZqRXyBNj#e9V6<address@hidden|bXJt}WGM&drBas8gPpg4G+*OE29`Ab?LX5F
zKIeMP(|Cx15y<-m<Oxh}WRz3ZJf7D0oZ-X&|7o31)0*E19C!O5&XCq~0;uRf+QA1b
zX{>7|eo$aa3kRw;nk>i|IC(Q;0c%?4;address@hidden;0)C|f
SJtz7Oyqvi?nJI*kF&F^X7ev$m
delta 107
address@hidden|`VlnOD22!$<yBUQi
zzh^99+93|&DjwV+!H~8~fR%ya{VqY)Kk1)y(snQa0l(6Lo)disUOwEsnkj^F@&_gl
G#(w~}wj;0r
diff --git a/pc-bios/optionrom/linuxboot.S b/pc-bios/optionrom/linuxboot.S
index 748c831..5bc0af0 100644
--- a/pc-bios/optionrom/linuxboot.S
+++ b/pc-bios/optionrom/linuxboot.S
@@ -76,14 +76,45 @@ boot_kernel:
copy_kernel:
+ /* Compute initrd address */
+ mov $0xe801, %ax
+ xor %cx, %cx
+ xor %dx, %dx
+ int $0x15
+
+ /* Output could be in AX/BX or CX/DX */
+ or %cx, %cx
+ jnz 1f
+ or %dx, %dx
+ jnz 1f
+ mov %ax, %cx
+ mov %bx, %dx
+1:
+
+ or %dx, %dx
+ jnz 2f
+ addw $1024, %cx /* add 1 MB */
+ movzwl %cx, %edi
+ shll $10, %edi /* convert to bytes */
+ jmp 3f
+
+2:
+ addw $16777216 >> 16, %dx /* add 16 MB */
+ movzwl %dx, %edi
+ shll $16, %edi /* convert to bytes */
+
+3:
+ read_fw FW_CFG_INITRD_SIZE
+ subl %eax, %edi
+ andl $-4096, %edi /* EDI = start of initrd */
/* We need to load the kernel into memory we can't access in 16 bit
mode, so let's get into 32 bit mode, write the kernel and jump
back again. */
/* Reserve space on the stack for our GDT descriptor. */
- mov %esp, %ebp
- sub $16, %esp
+ mov %esp, %ebp
+ sub $16, %esp
/* Now create the GDT descriptor */
movw $((3 * 8) - 1), -16(%bp)
@@ -108,10 +139,18 @@ copy_kernel:
/* We're now running in 16-bit CS, but 32-bit ES! */
/* Load kernel and initrd */
+ pushl %edi
+ read_fw_blob_addr32_edi(FW_CFG_INITRD)
read_fw_blob_addr32(FW_CFG_KERNEL)
- read_fw_blob_addr32(FW_CFG_INITRD)
read_fw_blob_addr32(FW_CFG_CMDLINE)
- read_fw_blob_addr32(FW_CFG_SETUP)
+
+ read_fw FW_CFG_SETUP_ADDR
+ mov %eax, %edi
+ mov %eax, %ebx
+ read_fw_blob_addr32_edi(FW_CFG_SETUP)
+
+ /* Update the header with the initrd address we chose above */
+ popl %es:0x218(%ebx)
/* And now jump into Linux! */
mov $0, %eax
diff --git a/pc-bios/optionrom/optionrom.h b/pc-bios/optionrom/optionrom.h
index ce43608..f1a9021 100644
--- a/pc-bios/optionrom/optionrom.h
+++ b/pc-bios/optionrom/optionrom.h
@@ -51,8 +51,6 @@
.endm
#define read_fw_blob_pre(var) \
- read_fw var ## _ADDR; \
- mov %eax, %edi; \
read_fw var ## _SIZE; \
mov %eax, %ecx; \
mov $var ## _DATA, %ax; \
@@ -68,6 +66,8 @@
* Clobbers: %eax, %edx, %es, %ecx, %edi
*/
#define read_fw_blob(var) \
+ read_fw var ## _ADDR; \
+ mov %eax, %edi; \
read_fw_blob_pre(var); \
/* old as(1) doesn't like this insn so emit the bytes instead: \
rep insb (%dx), %es:(%edi); \
@@ -80,7 +80,22 @@
*
* Clobbers: %eax, %edx, %es, %ecx, %edi
*/
-#define read_fw_blob_addr32(var) \
+#define read_fw_blob_addr32(var) \
+ read_fw var ## _ADDR; \
+ mov %eax, %edi; \
+ read_fw_blob_pre(var); \
+ /* old as(1) doesn't like this insn so emit the bytes instead: \
+ addr32 rep insb (%dx), %es:(%edi); \
+ */ \
+ .dc.b 0x67,0xf3,0x6c
+
+/*
+ * Read a blob from the fw_cfg device in forced addr32 mode, address is in
%edi.
+ * Requires _SIZE and _DATA values for the parameter.
+ *
+ * Clobbers: %eax, %edx, %edi, %es, %ecx
+ */
+#define read_fw_blob_addr32_edi(var) \
read_fw_blob_pre(var); \
/* old as(1) doesn't like this insn so emit the bytes instead: \
addr32 rep insb (%dx), %es:(%edi); \
--
1.8.3.1
- [Qemu-devel] [PULL 26/28] qemu-error: Add error_vreport(), (continued)
[Qemu-devel] [PULL 28/28] qemu-char: Fix reconnect socket error reporting, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 25/28] virtio-scsi: fix use-after-free of VirtIOSCSIReq, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 24/28] linuxboot: compute initrd loading address,
Paolo Bonzini <=
[Qemu-devel] [PULL 07/28] vl.c: Small coding style fix, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 16/28] accel: Move Xen registration code to xen-common.c, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 15/28] accel: Move KVM accel registration to kvm-all.c, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 10/28] accel: Simplify configure_accelerator() using AccelType *acc variable, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 11/28] accel: Move accel name lookup to separate function, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 14/28] accel: Report unknown accelerator as "not found" instead of "does not exist", Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 12/28] accel: Use QOM classes for accel types, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 09/28] accel: Create AccelType typedef, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 13/28] accel: Make AccelClass.available() optional, Paolo Bonzini, 2014/10/09
[Qemu-devel] [PULL 08/28] accel: Move accel code to accel.c, Paolo Bonzini, 2014/10/09