[PATCH v2 0/2] efi: arm: add support for earlycon on EFI framebuffer

[PATCH v2 0/2] efi: arm: add support for earlycon on EFI framebuffer

[Ard Biesheuvel]

Repurpose the existing EFI earlyprintk code to implement support for
'earlycon=efi' for arm64 systems, allowing the graphical console
to be used instead of the serial port for early debug output.

Changes since v1:
- Rename earlycon= argument to 'efifb' to emphasize that this is specific
  to the EFI framebuffer.
- Replace earlyprintk=efi entirely, rather than keep it alongside earlycon.
  Since earlycon is typically enabled (along with the infrastructure), and
  earlyprintk isn't, this does not result in a lot more code to be included,
  but does make it more likely that a given [distro] kernel has support for
  this enabled out of the box.
- Switch to write-combine mappings by default. This is the default for efifb,
  and is actually required on arm64, since device attributes do not tolerate
  unaligned accesses or other operations (such as DC ZVA) that rely on memory
  semantics. This requires ARCH_USE_MEMREMAP_PROT to be wired up, which is
  why a new patch #1 has been added.
- Since adding the 'ram' parameter for framebuffers in shared memory on cache
  coherent devices is trivial after the switch to WC mappings, fold the change
  into the main patch.

Cc: corbet@lwn.net
Cc: leif.lindholm@linaro.org
Cc: graeme.gregory@linaro.org
Cc: mingo@redhat.com
Cc: tglx@linutronix.de
Cc: linux-doc@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: agraf@suse.de
Cc: pjones@redhat.com

Ard Biesheuvel (2):
  x86: make ARCH_USE_MEMREMAP_PROT a generic Kconfig symbol
  efi: x86: convert x86 EFI earlyprintk into generic earlycon
    implementation

 Documentation/admin-guide/kernel-parameters.txt |   8 +-
 arch/Kconfig                                    |   3 +
 arch/x86/Kconfig                                |   5 +-
 arch/x86/Kconfig.debug                          |  10 -
 arch/x86/include/asm/efi.h                      |   1 -
 arch/x86/kernel/early_printk.c                  |   4 -
 arch/x86/platform/efi/Makefile                  |   1 -
 arch/x86/platform/efi/early_printk.c            | 240 --------------------
 drivers/firmware/efi/Kconfig                    |   6 +
 drivers/firmware/efi/Makefile                   |   1 +
 drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
 11 files changed, 226 insertions(+), 261 deletions(-)
 delete mode 100644 arch/x86/platform/efi/early_printk.c
 create mode 100644 drivers/firmware/efi/earlycon.c

-- 
2.20.1


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[PATCH v2 1/2] x86: make ARCH_USE_MEMREMAP_PROT a generic Kconfig symbol

[Ard Biesheuvel]

Turn ARCH_USE_MEMREMAP_PROT into a generic Kconfig symbol, and fix the
dependency expression to reflect that AMD_MEM_ENCRYPT depends on it,
instead of the other way around. This will permit ARCH_USE_MEMREMAP_PROT
to be selected by other architectures.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/Kconfig     | 3 +++
 arch/x86/Kconfig | 5 +----
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 4cfb6de48f79..9f0213213da8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -885,6 +885,9 @@ config HAVE_ARCH_PREL32_RELOCATIONS
 	  architectures, and don't require runtime relocation on relocatable
 	  kernels.
 
+config ARCH_USE_MEMREMAP_PROT
+	bool
+
 source "kernel/gcov/Kconfig"
 
 source "scripts/gcc-plugins/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 26387c7bf305..c0e9a77dc089 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1510,6 +1510,7 @@ config AMD_MEM_ENCRYPT
 	bool "AMD Secure Memory Encryption (SME) support"
 	depends on X86_64 && CPU_SUP_AMD
 	select DYNAMIC_PHYSICAL_MASK
+	select ARCH_USE_MEMREMAP_PROT
 	---help---
 	  Say yes to enable support for the encryption of system memory.
 	  This requires an AMD processor that supports Secure Memory
@@ -1529,10 +1530,6 @@ config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
 	  If set to N, then the encryption of system memory can be
 	  activated with the mem_encrypt=on command line option.
 
-config ARCH_USE_MEMREMAP_PROT
-	def_bool y
-	depends on AMD_MEM_ENCRYPT
-
 # Common NUMA Features
 config NUMA
 	bool "Numa Memory Allocation and Scheduler Support"
-- 
2.20.1


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[PATCH v2 2/2] efi: x86: convert x86 EFI earlyprintk into generic earlycon implementation

[Ard Biesheuvel]

Move the x86 EFI earlyprintk implementation to a shared location under
drivers/firmware and tweak it slightly so we can expose it as an earlycon
implementation (which is generic) rather than earlyprintk (which is only
implemented for a few architectures)

This also involves switching to write-combine mappings by default (which
is required on ARM since device mappings lack memory semantics, and so
memcpy/memset may not be used on them), and adding support for shared
memory framebuffers on cache coherent non-x86 systems (which do not
tolerate mismatched attributes)

Note that 32-bit ARM does not populate its struct screen_info early
enough for earlycon=efifb to work, so it is disabled there.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 Documentation/admin-guide/kernel-parameters.txt |   8 +-
 arch/x86/Kconfig.debug                          |  10 -
 arch/x86/include/asm/efi.h                      |   1 -
 arch/x86/kernel/early_printk.c                  |   4 -
 arch/x86/platform/efi/Makefile                  |   1 -
 arch/x86/platform/efi/early_printk.c            | 240 --------------------
 drivers/firmware/efi/Kconfig                    |   6 +
 drivers/firmware/efi/Makefile                   |   1 +
 drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
 9 files changed, 222 insertions(+), 257 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b799bcf67d7b..76dd3baa31e0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1073,9 +1073,15 @@
 			specified address. The serial port must already be
 			setup and configured. Options are not yet supported.
 
+		efifb,[options]
+			Start an early, unaccelerated console on the EFI
+			memory mapped framebuffer (if available). On cache
+			coherent non-x86 systems that use system memory for
+			the framebuffer, pass the 'ram' option so that it is
+			mapped with the correct attributes.
+
 	earlyprintk=	[X86,SH,ARM,M68k,S390]
 			earlyprintk=vga
-			earlyprintk=efi
 			earlyprintk=sclp
 			earlyprintk=xen
 			earlyprintk=serial[,ttySn[,baudrate]]
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 0723dff17e6c..15d0fbe27872 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -40,16 +40,6 @@ config EARLY_PRINTK_DBGP
 	  with klogd/syslogd or the X server. You should normally say N here,
 	  unless you want to debug such a crash. You need usb debug device.
 
-config EARLY_PRINTK_EFI
-	bool "Early printk via the EFI framebuffer"
-	depends on EFI && EARLY_PRINTK
-	select FONT_SUPPORT
-	---help---
-	  Write kernel log output directly into the EFI framebuffer.
-
-	  This is useful for kernel debugging when your machine crashes very
-	  early before the console code is initialized.
-
 config EARLY_PRINTK_USB_XDBC
 	bool "Early printk via the xHCI debug port"
 	depends on EARLY_PRINTK && PCI
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 107283b1eb1e..606a4b6a9812 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -170,7 +170,6 @@ static inline bool efi_runtime_supported(void)
 	return false;
 }
 
-extern struct console early_efi_console;
 extern void parse_efi_setup(u64 phys_addr, u32 data_len);
 
 extern void efifb_setup_from_dmi(struct screen_info *si, const char *opt);
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index 374a52fa5296..9b33904251a9 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -388,10 +388,6 @@ static int __init setup_early_printk(char *buf)
 		if (!strncmp(buf, "xen", 3))
 			early_console_register(&xenboot_console, keep);
 #endif
-#ifdef CONFIG_EARLY_PRINTK_EFI
-		if (!strncmp(buf, "efi", 3))
-			early_console_register(&early_efi_console, keep);
-#endif
 #ifdef CONFIG_EARLY_PRINTK_USB_XDBC
 		if (!strncmp(buf, "xdbc", 4))
 			early_xdbc_parse_parameter(buf + 4);
diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index e4dc3862d423..fe29f3f5d384 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -3,5 +3,4 @@ OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y
 OBJECT_FILES_NON_STANDARD_efi_stub_$(BITS).o := y
 
 obj-$(CONFIG_EFI) 		+= quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o
-obj-$(CONFIG_EARLY_PRINTK_EFI)	+= early_printk.o
 obj-$(CONFIG_EFI_MIXED)		+= efi_thunk_$(BITS).o
diff --git a/arch/x86/platform/efi/early_printk.c b/arch/x86/platform/efi/early_printk.c
deleted file mode 100644
index 7138bc7a265c..000000000000
--- a/arch/x86/platform/efi/early_printk.c
+++ /dev/null
@@ -1,240 +0,0 @@
-/*
- * Copyright (C) 2013 Intel Corporation; author Matt Fleming
- *
- *  This file is part of the Linux kernel, and is made available under
- *  the terms of the GNU General Public License version 2.
- */
-
-#include <linux/console.h>
-#include <linux/efi.h>
-#include <linux/font.h>
-#include <linux/io.h>
-#include <linux/kernel.h>
-#include <asm/setup.h>
-
-static const struct font_desc *font;
-static u32 efi_x, efi_y;
-static void *efi_fb;
-static bool early_efi_keep;
-
-/*
- * efi earlyprintk need use early_ioremap to map the framebuffer.
- * But early_ioremap is not usable for earlyprintk=efi,keep, ioremap should
- * be used instead. ioremap will be available after paging_init() which is
- * earlier than initcall callbacks. Thus adding this early initcall function
- * early_efi_map_fb to map the whole efi framebuffer.
- */
-static __init int early_efi_map_fb(void)
-{
-	u64 base, size;
-
-	if (!early_efi_keep)
-		return 0;
-
-	base = boot_params.screen_info.lfb_base;
-	if (boot_params.screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
-		base |= (u64)boot_params.screen_info.ext_lfb_base << 32;
-	size = boot_params.screen_info.lfb_size;
-	efi_fb = ioremap(base, size);
-
-	return efi_fb ? 0 : -ENOMEM;
-}
-early_initcall(early_efi_map_fb);
-
-/*
- * early_efi_map maps efi framebuffer region [start, start + len -1]
- * In case earlyprintk=efi,keep we have the whole framebuffer mapped already
- * so just return the offset efi_fb + start.
- */
-static __ref void *early_efi_map(unsigned long start, unsigned long len)
-{
-	u64 base;
-
-	base = boot_params.screen_info.lfb_base;
-	if (boot_params.screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
-		base |= (u64)boot_params.screen_info.ext_lfb_base << 32;
-
-	if (efi_fb)
-		return (efi_fb + start);
-	else
-		return early_ioremap(base + start, len);
-}
-
-static __ref void early_efi_unmap(void *addr, unsigned long len)
-{
-	if (!efi_fb)
-		early_iounmap(addr, len);
-}
-
-static void early_efi_clear_scanline(unsigned int y)
-{
-	unsigned long *dst;
-	u16 len;
-
-	len = boot_params.screen_info.lfb_linelength;
-	dst = early_efi_map(y*len, len);
-	if (!dst)
-		return;
-
-	memset(dst, 0, len);
-	early_efi_unmap(dst, len);
-}
-
-static void early_efi_scroll_up(void)
-{
-	unsigned long *dst, *src;
-	u16 len;
-	u32 i, height;
-
-	len = boot_params.screen_info.lfb_linelength;
-	height = boot_params.screen_info.lfb_height;
-
-	for (i = 0; i < height - font->height; i++) {
-		dst = early_efi_map(i*len, len);
-		if (!dst)
-			return;
-
-		src = early_efi_map((i + font->height) * len, len);
-		if (!src) {
-			early_efi_unmap(dst, len);
-			return;
-		}
-
-		memmove(dst, src, len);
-
-		early_efi_unmap(src, len);
-		early_efi_unmap(dst, len);
-	}
-}
-
-static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
-{
-	const u32 color_black = 0x00000000;
-	const u32 color_white = 0x00ffffff;
-	const u8 *src;
-	u8 s8;
-	int m;
-
-	src = font->data + c * font->height;
-	s8 = *(src + h);
-
-	for (m = 0; m < 8; m++) {
-		if ((s8 >> (7 - m)) & 1)
-			*dst = color_white;
-		else
-			*dst = color_black;
-		dst++;
-	}
-}
-
-static void
-early_efi_write(struct console *con, const char *str, unsigned int num)
-{
-	struct screen_info *si;
-	unsigned int len;
-	const char *s;
-	void *dst;
-
-	si = &boot_params.screen_info;
-	len = si->lfb_linelength;
-
-	while (num) {
-		unsigned int linemax;
-		unsigned int h, count = 0;
-
-		for (s = str; *s && *s != '\n'; s++) {
-			if (count == num)
-				break;
-			count++;
-		}
-
-		linemax = (si->lfb_width - efi_x) / font->width;
-		if (count > linemax)
-			count = linemax;
-
-		for (h = 0; h < font->height; h++) {
-			unsigned int n, x;
-
-			dst = early_efi_map((efi_y + h) * len, len);
-			if (!dst)
-				return;
-
-			s = str;
-			n = count;
-			x = efi_x;
-
-			while (n-- > 0) {
-				early_efi_write_char(dst + x*4, *s, h);
-				x += font->width;
-				s++;
-			}
-
-			early_efi_unmap(dst, len);
-		}
-
-		num -= count;
-		efi_x += count * font->width;
-		str += count;
-
-		if (num > 0 && *s == '\n') {
-			efi_x = 0;
-			efi_y += font->height;
-			str++;
-			num--;
-		}
-
-		if (efi_x + font->width > si->lfb_width) {
-			efi_x = 0;
-			efi_y += font->height;
-		}
-
-		if (efi_y + font->height > si->lfb_height) {
-			u32 i;
-
-			efi_y -= font->height;
-			early_efi_scroll_up();
-
-			for (i = 0; i < font->height; i++)
-				early_efi_clear_scanline(efi_y + i);
-		}
-	}
-}
-
-static __init int early_efi_setup(struct console *con, char *options)
-{
-	struct screen_info *si;
-	u16 xres, yres;
-	u32 i;
-
-	si = &boot_params.screen_info;
-	xres = si->lfb_width;
-	yres = si->lfb_height;
-
-	/*
-	 * early_efi_write_char() implicitly assumes a framebuffer with
-	 * 32-bits per pixel.
-	 */
-	if (si->lfb_depth != 32)
-		return -ENODEV;
-
-	font = get_default_font(xres, yres, -1, -1);
-	if (!font)
-		return -ENODEV;
-
-	efi_y = rounddown(yres, font->height) - font->height;
-	for (i = 0; i < (yres - efi_y) / font->height; i++)
-		early_efi_scroll_up();
-
-	/* early_console_register will unset CON_BOOT in case ,keep */
-	if (!(con->flags & CON_BOOT))
-		early_efi_keep = true;
-	return 0;
-}
-
-struct console early_efi_console = {
-	.name =		"earlyefi",
-	.write =	early_efi_write,
-	.setup =	early_efi_setup,
-	.flags =	CON_PRINTBUFFER,
-	.index =	-1,
-};
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 89110dfc7127..3b2f12fa620c 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -198,3 +198,9 @@ config EFI_DEV_PATH_PARSER
 	bool
 	depends on ACPI
 	default n
+
+config EFI_EARLYCON
+	def_bool y
+	depends on SERIAL_EARLYCON && !ARM
+	select FONT_SUPPORT
+	select ARCH_USE_MEMREMAP_PROT
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 5f9f5039de50..d2d0d2030620 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -30,5 +30,6 @@ arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
 obj-$(CONFIG_ARM64)			+= $(arm-obj-y)
 obj-$(CONFIG_EFI_CAPSULE_LOADER)	+= capsule-loader.o
+obj-$(CONFIG_EFI_EARLYCON)		+= earlycon.o
 obj-$(CONFIG_UEFI_CPER_ARM)		+= cper-arm.o
 obj-$(CONFIG_UEFI_CPER_X86)		+= cper-x86.o
diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c
new file mode 100644
index 000000000000..163d8204b190
--- /dev/null
+++ b/drivers/firmware/efi/earlycon.c
@@ -0,0 +1,208 @@
+/*
+ * Copyright (C) 2013 Intel Corporation; author Matt Fleming
+ *
+ *  This file is part of the Linux kernel, and is made available under
+ *  the terms of the GNU General Public License version 2.
+ */
+
+#include <linux/console.h>
+#include <linux/efi.h>
+#include <linux/font.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/serial_core.h>
+#include <linux/screen_info.h>
+
+#include <asm/early_ioremap.h>
+
+static const struct font_desc *font;
+static u32 efi_x, efi_y;
+static u64 fb_base;
+static pgprot_t fb_prot;
+
+static __ref void *efi_earlycon_map(unsigned long start, unsigned long len)
+{
+	return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot));
+}
+
+static __ref void efi_earlycon_unmap(void *addr, unsigned long len)
+{
+	early_memunmap(addr, len);
+}
+
+static void efi_earlycon_clear_scanline(unsigned int y)
+{
+	unsigned long *dst;
+	u16 len;
+
+	len = screen_info.lfb_linelength;
+	dst = efi_earlycon_map(y*len, len);
+	if (!dst)
+		return;
+
+	memset(dst, 0, len);
+	efi_earlycon_unmap(dst, len);
+}
+
+static void efi_earlycon_scroll_up(void)
+{
+	unsigned long *dst, *src;
+	u16 len;
+	u32 i, height;
+
+	len = screen_info.lfb_linelength;
+	height = screen_info.lfb_height;
+
+	for (i = 0; i < height - font->height; i++) {
+		dst = efi_earlycon_map(i*len, len);
+		if (!dst)
+			return;
+
+		src = efi_earlycon_map((i + font->height) * len, len);
+		if (!src) {
+			efi_earlycon_unmap(dst, len);
+			return;
+		}
+
+		memmove(dst, src, len);
+
+		efi_earlycon_unmap(src, len);
+		efi_earlycon_unmap(dst, len);
+	}
+}
+
+static void efi_earlycon_write_char(u32 *dst, unsigned char c, unsigned int h)
+{
+	const u32 color_black = 0x00000000;
+	const u32 color_white = 0x00ffffff;
+	const u8 *src;
+	u8 s8;
+	int m;
+
+	src = font->data + c * font->height;
+	s8 = *(src + h);
+
+	for (m = 0; m < 8; m++) {
+		if ((s8 >> (7 - m)) & 1)
+			*dst = color_white;
+		else
+			*dst = color_black;
+		dst++;
+	}
+}
+
+static void
+efi_earlycon_write(struct console *con, const char *str, unsigned int num)
+{
+	struct screen_info *si;
+	unsigned int len;
+	const char *s;
+	void *dst;
+
+	si = &screen_info;
+	len = si->lfb_linelength;
+
+	while (num) {
+		unsigned int linemax;
+		unsigned int h, count = 0;
+
+		for (s = str; *s && *s != '\n'; s++) {
+			if (count == num)
+				break;
+			count++;
+		}
+
+		linemax = (si->lfb_width - efi_x) / font->width;
+		if (count > linemax)
+			count = linemax;
+
+		for (h = 0; h < font->height; h++) {
+			unsigned int n, x;
+
+			dst = efi_earlycon_map((efi_y + h) * len, len);
+			if (!dst)
+				return;
+
+			s = str;
+			n = count;
+			x = efi_x;
+
+			while (n-- > 0) {
+				efi_earlycon_write_char(dst + x*4, *s, h);
+				x += font->width;
+				s++;
+			}
+
+			efi_earlycon_unmap(dst, len);
+		}
+
+		num -= count;
+		efi_x += count * font->width;
+		str += count;
+
+		if (num > 0 && *s == '\n') {
+			efi_x = 0;
+			efi_y += font->height;
+			str++;
+			num--;
+		}
+
+		if (efi_x + font->width > si->lfb_width) {
+			efi_x = 0;
+			efi_y += font->height;
+		}
+
+		if (efi_y + font->height > si->lfb_height) {
+			u32 i;
+
+			efi_y -= font->height;
+			efi_earlycon_scroll_up();
+
+			for (i = 0; i < font->height; i++)
+				efi_earlycon_clear_scanline(efi_y + i);
+		}
+	}
+}
+
+static int __init efi_earlycon_setup(struct earlycon_device *device,
+				     const char *opt)
+{
+	struct screen_info *si;
+	u16 xres, yres;
+	u32 i;
+
+	if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
+		return -ENODEV;
+
+	fb_base = screen_info.lfb_base;
+	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+		fb_base |= (u64)screen_info.ext_lfb_base << 32;
+
+	if (opt && !strcmp(opt, "ram"))
+		fb_prot = PAGE_KERNEL;
+	else
+		fb_prot = pgprot_writecombine(PAGE_KERNEL);
+
+	si = &screen_info;
+	xres = si->lfb_width;
+	yres = si->lfb_height;
+
+	/*
+	 * efi_earlycon_write_char() implicitly assumes a framebuffer with
+	 * 32-bits per pixel.
+	 */
+	if (si->lfb_depth != 32)
+		return -ENODEV;
+
+	font = get_default_font(xres, yres, -1, -1);
+	if (!font)
+		return -ENODEV;
+
+	efi_y = rounddown(yres, font->height) - font->height;
+	for (i = 0; i < (yres - efi_y) / font->height; i++)
+		efi_earlycon_scroll_up();
+
+	device->con->write = efi_earlycon_write;
+	return 0;
+}
+EARLYCON_DECLARE(efifb, efi_earlycon_setup);
-- 
2.20.1


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Re: [PATCH v2 2/2] efi: x86: convert x86 EFI earlyprintk into generic earlycon implementation

[Alexander Graf]

On 01/29/2019 10:21 AM, Ard Biesheuvel wrote:
> Move the x86 EFI earlyprintk implementation to a shared location under
> drivers/firmware and tweak it slightly so we can expose it as an earlycon
> implementation (which is generic) rather than earlyprintk (which is only
> implemented for a few architectures)
>
> This also involves switching to write-combine mappings by default (which
> is required on ARM since device mappings lack memory semantics, and so
> memcpy/memset may not be used on them), and adding support for shared
> memory framebuffers on cache coherent non-x86 systems (which do not
> tolerate mismatched attributes)
>
> Note that 32-bit ARM does not populate its struct screen_info early
> enough for earlycon=efifb to work, so it is disabled there.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>   Documentation/admin-guide/kernel-parameters.txt |   8 +-
>   arch/x86/Kconfig.debug                          |  10 -
>   arch/x86/include/asm/efi.h                      |   1 -
>   arch/x86/kernel/early_printk.c                  |   4 -
>   arch/x86/platform/efi/Makefile                  |   1 -
>   arch/x86/platform/efi/early_printk.c            | 240 --------------------
>   drivers/firmware/efi/Kconfig                    |   6 +
>   drivers/firmware/efi/Makefile                   |   1 +
>   drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
>   9 files changed, 222 insertions(+), 257 deletions(-)
>

[...]

> +static int __init efi_earlycon_setup(struct earlycon_device *device,
> +				     const char *opt)
> +{
> +	struct screen_info *si;
> +	u16 xres, yres;
> +	u32 i;
> +
> +	if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> +		return -ENODEV;
> +
> +	fb_base = screen_info.lfb_base;
> +	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> +		fb_base |= (u64)screen_info.ext_lfb_base << 32;
> +
> +	if (opt && !strcmp(opt, "ram"))
> +		fb_prot = PAGE_KERNEL;
> +	else
> +		fb_prot = pgprot_writecombine(PAGE_KERNEL);

Can you determine the default from the UEFI memory map?

Also, doesn't the current logic map it as WC on x86 too? Is that 
intentional?


Alex

> +
> +	si = &screen_info;
> +	xres = si->lfb_width;
> +	yres = si->lfb_height;
> +
> +	/*
> +	 * efi_earlycon_write_char() implicitly assumes a framebuffer with
> +	 * 32-bits per pixel.
> +	 */
> +	if (si->lfb_depth != 32)
> +		return -ENODEV;
> +
> +	font = get_default_font(xres, yres, -1, -1);
> +	if (!font)
> +		return -ENODEV;
> +
> +	efi_y = rounddown(yres, font->height) - font->height;
> +	for (i = 0; i < (yres - efi_y) / font->height; i++)
> +		efi_earlycon_scroll_up();
> +
> +	device->con->write = efi_earlycon_write;
> +	return 0;
> +}
> +EARLYCON_DECLARE(efifb, efi_earlycon_setup);



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Re: [PATCH v2 2/2] efi: x86: convert x86 EFI earlyprintk into generic earlycon implementation

[Ard Biesheuvel]

Hi Alex,

On Tue, 29 Jan 2019 at 14:37, Alexander Graf <agraf@suse.de> wrote:
>
> On 01/29/2019 10:21 AM, Ard Biesheuvel wrote:
> > Move the x86 EFI earlyprintk implementation to a shared location under
> > drivers/firmware and tweak it slightly so we can expose it as an earlycon
> > implementation (which is generic) rather than earlyprintk (which is only
> > implemented for a few architectures)
> >
> > This also involves switching to write-combine mappings by default (which
> > is required on ARM since device mappings lack memory semantics, and so
> > memcpy/memset may not be used on them), and adding support for shared
> > memory framebuffers on cache coherent non-x86 systems (which do not
> > tolerate mismatched attributes)
> >
> > Note that 32-bit ARM does not populate its struct screen_info early
> > enough for earlycon=efifb to work, so it is disabled there.
> >
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >   Documentation/admin-guide/kernel-parameters.txt |   8 +-
> >   arch/x86/Kconfig.debug                          |  10 -
> >   arch/x86/include/asm/efi.h                      |   1 -
> >   arch/x86/kernel/early_printk.c                  |   4 -
> >   arch/x86/platform/efi/Makefile                  |   1 -
> >   arch/x86/platform/efi/early_printk.c            | 240 --------------------
> >   drivers/firmware/efi/Kconfig                    |   6 +
> >   drivers/firmware/efi/Makefile                   |   1 +
> >   drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
> >   9 files changed, 222 insertions(+), 257 deletions(-)
> >
>
> [...]
>
> > +static int __init efi_earlycon_setup(struct earlycon_device *device,
> > +                                  const char *opt)
> > +{
> > +     struct screen_info *si;
> > +     u16 xres, yres;
> > +     u32 i;
> > +
> > +     if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> > +             return -ENODEV;
> > +
> > +     fb_base = screen_info.lfb_base;
> > +     if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> > +             fb_base |= (u64)screen_info.ext_lfb_base << 32;
> > +
> > +     if (opt && !strcmp(opt, "ram"))
> > +             fb_prot = PAGE_KERNEL;
> > +     else
> > +             fb_prot = pgprot_writecombine(PAGE_KERNEL);
>
> Can you determine the default from the UEFI memory map?
>

No. This is being called way before we parse the system table and the
memory map. Given that this is debug code, duplicating a significant
chunk of that work here (and run the risk of crashing here due to
unexpected contents in those tables) is not a great idea imo.

> Also, doesn't the current logic map it as WC on x86 too? Is that
> intentional?
>

Yes. As mentioned in the cover letter, this aligns it with efifb which
also uses WC by default (although there, it can be overridden for
performance reasons, but due to the debug nature of earlycon, this
doesn't matter, since higher performance only makes it more difficult
to capture the log on your phone camera)


> > +
> > +     si = &screen_info;
> > +     xres = si->lfb_width;
> > +     yres = si->lfb_height;
> > +
> > +     /*
> > +      * efi_earlycon_write_char() implicitly assumes a framebuffer with
> > +      * 32-bits per pixel.
> > +      */
> > +     if (si->lfb_depth != 32)
> > +             return -ENODEV;
> > +
> > +     font = get_default_font(xres, yres, -1, -1);
> > +     if (!font)
> > +             return -ENODEV;
> > +
> > +     efi_y = rounddown(yres, font->height) - font->height;
> > +     for (i = 0; i < (yres - efi_y) / font->height; i++)
> > +             efi_earlycon_scroll_up();
> > +
> > +     device->con->write = efi_earlycon_write;
> > +     return 0;
> > +}
> > +EARLYCON_DECLARE(efifb, efi_earlycon_setup);
>
>

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Re: [PATCH v2 2/2] efi: x86: convert x86 EFI earlyprintk into generic earlycon implementation

[Alexander Graf]

On 01/29/2019 02:41 PM, Ard Biesheuvel wrote:
> Hi Alex,
>
> On Tue, 29 Jan 2019 at 14:37, Alexander Graf <agraf@suse.de> wrote:
>> On 01/29/2019 10:21 AM, Ard Biesheuvel wrote:
>>> Move the x86 EFI earlyprintk implementation to a shared location under
>>> drivers/firmware and tweak it slightly so we can expose it as an earlycon
>>> implementation (which is generic) rather than earlyprintk (which is only
>>> implemented for a few architectures)
>>>
>>> This also involves switching to write-combine mappings by default (which
>>> is required on ARM since device mappings lack memory semantics, and so
>>> memcpy/memset may not be used on them), and adding support for shared
>>> memory framebuffers on cache coherent non-x86 systems (which do not
>>> tolerate mismatched attributes)
>>>
>>> Note that 32-bit ARM does not populate its struct screen_info early
>>> enough for earlycon=efifb to work, so it is disabled there.
>>>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>> ---
>>>    Documentation/admin-guide/kernel-parameters.txt |   8 +-
>>>    arch/x86/Kconfig.debug                          |  10 -
>>>    arch/x86/include/asm/efi.h                      |   1 -
>>>    arch/x86/kernel/early_printk.c                  |   4 -
>>>    arch/x86/platform/efi/Makefile                  |   1 -
>>>    arch/x86/platform/efi/early_printk.c            | 240 --------------------
>>>    drivers/firmware/efi/Kconfig                    |   6 +
>>>    drivers/firmware/efi/Makefile                   |   1 +
>>>    drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
>>>    9 files changed, 222 insertions(+), 257 deletions(-)
>>>
>> [...]
>>
>>> +static int __init efi_earlycon_setup(struct earlycon_device *device,
>>> +                                  const char *opt)
>>> +{
>>> +     struct screen_info *si;
>>> +     u16 xres, yres;
>>> +     u32 i;
>>> +
>>> +     if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
>>> +             return -ENODEV;
>>> +
>>> +     fb_base = screen_info.lfb_base;
>>> +     if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
>>> +             fb_base |= (u64)screen_info.ext_lfb_base << 32;
>>> +
>>> +     if (opt && !strcmp(opt, "ram"))
>>> +             fb_prot = PAGE_KERNEL;
>>> +     else
>>> +             fb_prot = pgprot_writecombine(PAGE_KERNEL);
>> Can you determine the default from the UEFI memory map?
>>
> No. This is being called way before we parse the system table and the
> memory map. Given that this is debug code, duplicating a significant
> chunk of that work here (and run the risk of crashing here due to
> unexpected contents in those tables) is not a great idea imo.

I see. Maybe we will want to have something there, but I tend to agree 
that for now we should keep bits as simple as possible.

>
>> Also, doesn't the current logic map it as WC on x86 too? Is that
>> intentional?
>>
> Yes. As mentioned in the cover letter, this aligns it with efifb which
> also uses WC by default (although there, it can be overridden for
> performance reasons, but due to the debug nature of earlycon, this
> doesn't matter, since higher performance only makes it more difficult
> to capture the log on your phone camera)

Well, the cover letter really only talks about arm :). But yeah, I think 
it's probably a good idea to map it WC regardless.

Overall, I would've preferred to have a larger patch set with more, but 
smaller changes that refactor the code. But it seems to be reviewable 
enough still. Let's cross our fingers it doesn't break :).


Reviewed-by: Alexander Graf <agraf@suse.de>

Thanks,

Alex


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Re: [PATCH v2 2/2] efi: x86: convert x86 EFI earlyprintk into generic earlycon implementation

[Ard Biesheuvel]

On Tue, 29 Jan 2019 at 15:04, Alexander Graf <agraf@suse.de> wrote:
>
> On 01/29/2019 02:41 PM, Ard Biesheuvel wrote:
> > Hi Alex,
> >
> > On Tue, 29 Jan 2019 at 14:37, Alexander Graf <agraf@suse.de> wrote:
> >> On 01/29/2019 10:21 AM, Ard Biesheuvel wrote:
> >>> Move the x86 EFI earlyprintk implementation to a shared location under
> >>> drivers/firmware and tweak it slightly so we can expose it as an earlycon
> >>> implementation (which is generic) rather than earlyprintk (which is only
> >>> implemented for a few architectures)
> >>>
> >>> This also involves switching to write-combine mappings by default (which
> >>> is required on ARM since device mappings lack memory semantics, and so
> >>> memcpy/memset may not be used on them), and adding support for shared
> >>> memory framebuffers on cache coherent non-x86 systems (which do not
> >>> tolerate mismatched attributes)
> >>>
> >>> Note that 32-bit ARM does not populate its struct screen_info early
> >>> enough for earlycon=efifb to work, so it is disabled there.
> >>>
> >>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>> ---
> >>>    Documentation/admin-guide/kernel-parameters.txt |   8 +-
> >>>    arch/x86/Kconfig.debug                          |  10 -
> >>>    arch/x86/include/asm/efi.h                      |   1 -
> >>>    arch/x86/kernel/early_printk.c                  |   4 -
> >>>    arch/x86/platform/efi/Makefile                  |   1 -
> >>>    arch/x86/platform/efi/early_printk.c            | 240 --------------------
> >>>    drivers/firmware/efi/Kconfig                    |   6 +
> >>>    drivers/firmware/efi/Makefile                   |   1 +
> >>>    drivers/firmware/efi/earlycon.c                 | 208 +++++++++++++++++
> >>>    9 files changed, 222 insertions(+), 257 deletions(-)
> >>>
> >> [...]
> >>
> >>> +static int __init efi_earlycon_setup(struct earlycon_device *device,
> >>> +                                  const char *opt)
> >>> +{
> >>> +     struct screen_info *si;
> >>> +     u16 xres, yres;
> >>> +     u32 i;
> >>> +
> >>> +     if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
> >>> +             return -ENODEV;
> >>> +
> >>> +     fb_base = screen_info.lfb_base;
> >>> +     if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
> >>> +             fb_base |= (u64)screen_info.ext_lfb_base << 32;
> >>> +
> >>> +     if (opt && !strcmp(opt, "ram"))
> >>> +             fb_prot = PAGE_KERNEL;
> >>> +     else
> >>> +             fb_prot = pgprot_writecombine(PAGE_KERNEL);
> >> Can you determine the default from the UEFI memory map?
> >>
> > No. This is being called way before we parse the system table and the
> > memory map. Given that this is debug code, duplicating a significant
> > chunk of that work here (and run the risk of crashing here due to
> > unexpected contents in those tables) is not a great idea imo.
>
> I see. Maybe we will want to have something there, but I tend to agree
> that for now we should keep bits as simple as possible.
>
> >
> >> Also, doesn't the current logic map it as WC on x86 too? Is that
> >> intentional?
> >>
> > Yes. As mentioned in the cover letter, this aligns it with efifb which
> > also uses WC by default (although there, it can be overridden for
> > performance reasons, but due to the debug nature of earlycon, this
> > doesn't matter, since higher performance only makes it more difficult
> > to capture the log on your phone camera)
>
> Well, the cover letter really only talks about arm :). But yeah, I think
> it's probably a good idea to map it WC regardless.
>

Fair enough.

> Overall, I would've preferred to have a larger patch set with more, but
> smaller changes that refactor the code. But it seems to be reviewable
> enough still. Let's cross our fingers it doesn't break :).
>
>
> Reviewed-by: Alexander Graf <agraf@suse.de>
>

Thanks

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