From 48972f8cad24eb4462c97ea68003e2dd35be0444 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcus=20H=C3=A4hnel?= <marcus.haehnel@kernkonzept.com>
Date: Wed, 20 Oct 2021 14:55:04 +0200
Subject: [PATCH] optionrom: add a DMA-enabled multiboot ROM
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Add a new option rom for the multiboot loader, using DMA transfers to copy
data instead of "rep insb".

This significantly lowers QEMU's startup latency by a factor of about 40,
for example, going from 30sec to 0.8sec when loading modules of 120MB
in size.

Signed-off-by: Marcus Hähnel <marcus.haehnel@kernkonzept.com>
Signed-off-by: Adam Lackorzynski <adam@l4re.org>
[Modified to keep the non-DMA code depending on #ifdef USE_FW_CFG_DMA;
 do not write below stack. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 pc-bios/meson.build               |   1 +
 pc-bios/multiboot_dma.bin         | Bin 0 -> 1024 bytes
 pc-bios/optionrom/Makefile        |   4 +-
 pc-bios/optionrom/multiboot.S     |   4 +-
 pc-bios/optionrom/multiboot_dma.S |   2 +
 pc-bios/optionrom/optionrom.h     |  66 ++++++++++++++++++++++++++++++
 6 files changed, 72 insertions(+), 5 deletions(-)
 create mode 100644 pc-bios/multiboot_dma.bin
 create mode 100644 pc-bios/optionrom/multiboot_dma.S

diff --git a/pc-bios/meson.build b/pc-bios/meson.build
index a44c9bc127..b40ff3f2bd 100644
--- a/pc-bios/meson.build
+++ b/pc-bios/meson.build
@@ -63,6 +63,7 @@ blobs = files(
   'petalogix-s3adsp1800.dtb',
   'petalogix-ml605.dtb',
   'multiboot.bin',
+  'multiboot_dma.bin',
   'linuxboot.bin',
   'linuxboot_dma.bin',
   'kvmvapic.bin',
diff --git a/pc-bios/multiboot_dma.bin b/pc-bios/multiboot_dma.bin
new file mode 100644
index 0000000000000000000000000000000000000000..c0e2c3102a3358207c61d3ae113524fb6007abc3
GIT binary patch
literal 1024
zcmWGt#dMkhE0AGO3CIgzWP(XPVtNi|+kgdoPW0XQ^(U?8MB2dzENML#(+)mlN$Y%^
z#&|QW`K3Zy^BaS-gD+Y7UZ!=+tzk-IJe-==DaXLDn}Z>>Q;vn9TkZ~1YNs3<Lt3}o
zJ(x5HLz>}%z5_eB8FmS<zTYLt`X=q*0}f<@|3q5n!5v(9<&UTFpHB-<Gdz$MuuFtB
z?R^^m$+W<<9b61T3~Br)(gM;tAEfc0*d@W5_C7tWn?(gAxbols|Nl!rq%|KAz;F7&
z7c6}b&I+Z?NJ(4F!jO`-(10NgBz7Rp@OGNv|K{T?X*)$27#PxaD7;``NZS?Q=o@@i
zv`APjJ+0IKPa5O-lukPxhP2k(rB@99r|n{35MW5Lw$ouKF>5}~qL$WNE5KN)qL$X}
z%97T4pj1jNt(!H?@=%eWS{kz}N1ElKV)nGoLx%rfpHfR>uKn}+a9ZOlkQr$QUvZ_R
zb&7E?q^9vRim@@I?O<eJVBl9ekec>ikAY!_00RR<--W&#eFyp;^u0*i!NHKWO8^u&
zpil+{G7R&d=scLVgB_3basKn+h6e)Dc8RdQ=RX;^gNs3sf&WB6=L7x|X}cs?-*>a9
z@SlJL=$Gar0%<!0@ECRw6fwA+a(D;RhPB%NA2Kj7ykulx-~gvQ2=V_v0|UdX^9*2m
t5|p0D0Od0<s55L~Vqge#^$lgnEzK#(Ov=wMQOL<pOi3+*7%)oa0{}$1FAx9#

literal 0
HcmV?d00001

diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 3482508a86..5d55d25acc 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -2,7 +2,7 @@ include config.mak
 SRC_DIR := $(TOPSRC_DIR)/pc-bios/optionrom
 VPATH = $(SRC_DIR)
 
-all: multiboot.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
+all: multiboot.bin multiboot_dma.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
 # Dummy command so that make thinks it has done something
 	@true
 
@@ -41,8 +41,6 @@ override CFLAGS += $(call cc-option, $(Wa)-32)
 LD_I386_EMULATION ?= elf_i386
 override LDFLAGS = -m $(LD_I386_EMULATION) -T $(SRC_DIR)/flat.lds
 
-all: multiboot.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
-
 pvh.img: pvh.o pvh_main.o
 
 %.o: %.S
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S
index b7efe4de34..181a4b03a3 100644
--- a/pc-bios/optionrom/multiboot.S
+++ b/pc-bios/optionrom/multiboot.S
@@ -68,7 +68,7 @@ run_multiboot:
 	mov		%eax, %es
 
 	/* Read the bootinfo struct into RAM */
-	read_fw_blob(FW_CFG_INITRD)
+	read_fw_blob_dma(FW_CFG_INITRD)
 
 	/* FS = bootinfo_struct */
 	read_fw		FW_CFG_INITRD_ADDR
@@ -188,7 +188,7 @@ prot_mode:
 	movl		%eax, %gs
 
 	/* Read the kernel and modules into RAM */
-	read_fw_blob(FW_CFG_KERNEL)
+	read_fw_blob_dma(FW_CFG_KERNEL)
 
 	/* Jump off to the kernel */
 	read_fw		FW_CFG_KERNEL_ENTRY
diff --git a/pc-bios/optionrom/multiboot_dma.S b/pc-bios/optionrom/multiboot_dma.S
new file mode 100644
index 0000000000..d809af3e23
--- /dev/null
+++ b/pc-bios/optionrom/multiboot_dma.S
@@ -0,0 +1,2 @@
+#define USE_FW_CFG_DMA 1
+#include "multiboot.S"
diff --git a/pc-bios/optionrom/optionrom.h b/pc-bios/optionrom/optionrom.h
index a2b612f1a7..8d74c0ddf3 100644
--- a/pc-bios/optionrom/optionrom.h
+++ b/pc-bios/optionrom/optionrom.h
@@ -37,6 +37,17 @@
 #define BIOS_CFG_IOPORT_CFG	0x510
 #define BIOS_CFG_IOPORT_DATA	0x511
 
+#define FW_CFG_DMA_CTL_ERROR   0x01
+#define FW_CFG_DMA_CTL_READ    0x02
+#define FW_CFG_DMA_CTL_SKIP    0x04
+#define FW_CFG_DMA_CTL_SELECT  0x08
+#define FW_CFG_DMA_CTL_WRITE   0x10
+
+#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647ULL /* "QEMU CFG" */
+
+#define BIOS_CFG_DMA_ADDR_HIGH  0x514
+#define BIOS_CFG_DMA_ADDR_LOW   0x518
+
 /* Break the translation block flow so -d cpu shows us values */
 #define DEBUG_HERE \
 	jmp		1f;				\
@@ -62,6 +73,61 @@
 	bswap		%eax
 .endm
 
+
+/*
+ * Read data from the fw_cfg device using DMA.
+ * Clobbers:	%edx, %eax, ADDR, SIZE, memory[%esp-16] to memory[%esp]
+ */
+.macro read_fw_dma VAR, SIZE, ADDR
+        /* Address */
+	bswapl		\ADDR
+	pushl		\ADDR
+
+	/* We only support 32 bit target addresses */
+	xorl		%eax, %eax
+	pushl		%eax
+	mov		$BIOS_CFG_DMA_ADDR_HIGH, %dx
+	outl		%eax, (%dx)
+
+	/* Size */
+	bswapl		\SIZE
+	pushl		\SIZE
+
+        /* Control */
+	movl		$(\VAR << 16) | (FW_CFG_DMA_CTL_READ | FW_CFG_DMA_CTL_SELECT), %eax
+	bswapl		%eax
+	pushl		%eax
+
+	movl		%esp, %eax /* Address of the struct we generated */
+	bswapl		%eax
+	mov		$BIOS_CFG_DMA_ADDR_LOW, %dx
+	outl		%eax, (%dx) /* Initiate DMA */
+
+1:  mov		(%esp), %eax /* Wait for completion */
+	bswapl		%eax
+	testl		$~FW_CFG_DMA_CTL_ERROR, %eax
+	jnz		1b
+       addl            $16, %esp
+.endm
+
+
+/*
+ * Read a blob from the fw_cfg device using DMA
+ * Requires _ADDR, _SIZE and _DATA values for the parameter.
+ *
+ * Clobbers:	%eax, %edx, %es, %ecx, %edi and adresses %esp-20 to %esp
+ */
+#ifdef USE_FW_CFG_DMA
+#define read_fw_blob_dma(var) \
+	read_fw		var ## _SIZE; \
+	mov		%eax, %ecx; \
+	read_fw		var ## _ADDR; \
+	mov		%eax, %edi ;\
+	read_fw_dma	var ## _DATA, %ecx, %edi
+#else
+#define read_fw_blob_dma(var) read_fw_blob(var)
+#endif
+
 #define read_fw_blob_pre(var)				\
 	read_fw		var ## _SIZE;			\
 	mov		%eax, %ecx;			\