From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52571) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XbQMg-0000bY-Tj for qemu-devel@nongnu.org; Tue, 07 Oct 2014 04:43:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XbQMa-0002wv-IT for qemu-devel@nongnu.org; Tue, 07 Oct 2014 04:43:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18929) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XbQMa-0002wn-BI for qemu-devel@nongnu.org; Tue, 07 Oct 2014 04:43:20 -0400 Date: Tue, 7 Oct 2014 11:46:51 +0300 From: "Michael S. Tsirkin" Message-ID: <20141007084651.GA3797@redhat.com> References: <1412606997-13290-1-git-send-email-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412606997-13290-1-git-send-email-pbonzini@redhat.com> Subject: Re: [Qemu-devel] [PATCH] linuxboot: compute initrd loading address List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: jsnow@redhat.com, qemu-devel@nongnu.org, agraf@suse.de On Mon, Oct 06, 2014 at 04:49:57PM +0200, Paolo Bonzini wrote: > 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. > > Signed-off-by: Paolo Bonzini Acked-by: Michael S. Tsirkin OK, and we need something similar for multiboot.S? Also - can we drop FW_CFG_INITRD_ADDR and the patching in load_linux now (unless running a compat machine type)? > --- > 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 zKIeMP(|Cx15y<-m zX{>7|eo$aa3kRw;nk>i|IC(Q;0c%?4;T_@=t7IoTF$qbirKj~bOE57or0rk;0)C|f > SJtz7Oyqvi?nJI*kF&F^X7ev$m > > delta 107 > zcmZqRXyBNj#azSGI8k@yWCKP?#+1okj0#LU*e5$O$xYtNXvD|`VlnOD22!$ 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); \ > -- > 2.1.0