x86: Introduce a new option --reuse-video-type

After commit 060eee58 "x86: use old screen_info if needed", kexec-tools
will force use old screen_info and vga type if failed to determine
current vga type. But it is not always a good idea.

Currently kernel hanging is inspected on some hyper-v VMs after this
commit, because hyperv_fb will mimic EFI (or VESA) VGA on first boot
up, but after the real driver is loaded, it will switch to new mode
and no longer compatible with EFI/VESA VGA. Keep setting
orig_video_isVGA to EFI/VESA VGA flag will get wrong driver loaded and
try to manipulate the framebuffer in a wrong way.

We can't ensure this won't happen on other framebuffer drivers, But
it's a helpful feature if the framebuffer drivers just work. So this
patch introduce a --reuse-video-type options to let user decide if the
old screen_info hould be used unconditional or not.

Signed-off-by: Kairui Song <kasong@redhat.com>
Reviewed-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

3 files changed, 9 insertions, 2 deletions

diff --git a/kexec/arch/i386/include/arch/options.h b/kexec/arch/i386/include/arch/options.h
index c113a83..0e57951 100644
--- a/kexec/arch/i386/include/arch/options.h
+++ b/kexec/arch/i386/include/arch/options.h
@@ -32,6 +32,7 @@
 #define OPT_ENTRY_32BIT		(OPT_ARCH_MAX+10)
 #define OPT_PASS_MEMMAP_CMDLINE	(OPT_ARCH_MAX+11)
 #define OPT_NOEFI		(OPT_ARCH_MAX+12)
+#define OPT_REUSE_VIDEO_TYPE	(OPT_ARCH_MAX+13)
 
 /* Options relevant to the architecture (excluding loader-specific ones): */
 #define KEXEC_ARCH_OPTIONS \
@@ -45,6 +46,7 @@
 	{ "elf64-core-headers", 0, 0, OPT_ELF64_CORE }, \
 	{ "pass-memmap-cmdline", 0, 0, OPT_PASS_MEMMAP_CMDLINE }, \
 	{ "noefi", 0, 0, OPT_NOEFI}, \
+	{ "reuse-video-type", 0, 0, OPT_REUSE_VIDEO_TYPE },	\
 
 #define KEXEC_ARCH_OPT_STR KEXEC_OPT_STR ""
 
diff --git a/kexec/arch/i386/kexec-x86.h b/kexec/arch/i386/kexec-x86.h
index 51855f8..c2bcd37 100644
--- a/kexec/arch/i386/kexec-x86.h
+++ b/kexec/arch/i386/kexec-x86.h
@@ -52,6 +52,7 @@ struct arch_options_t {
 	enum coretype	core_header_type;
 	uint8_t  	pass_memmap_cmdline;
 	uint8_t		noefi;
+	uint8_t		reuse_video_type;
 };
 
 int multiboot_x86_probe(const char *buf, off_t len);
diff --git a/kexec/arch/i386/x86-linux-setup.c b/kexec/arch/i386/x86-linux-setup.c
index 1bd408b..8fad115 100644
--- a/kexec/arch/i386/x86-linux-setup.c
+++ b/kexec/arch/i386/x86-linux-setup.c
@@ -144,7 +144,7 @@ static int setup_linux_vesafb(struct x86_linux_param_header *real_mode)
 	} else if (0 == strcmp(fix.id, "EFI VGA")) {
 		/* VIDEO_TYPE_EFI */
 		real_mode->orig_video_isVGA = 0x70;
-	} else {
+	} else if (arch_options.reuse_video_type) {
 		int err;
 		off_t offset = offsetof(typeof(*real_mode), orig_video_isVGA);
 
@@ -152,6 +152,10 @@ static int setup_linux_vesafb(struct x86_linux_param_header *real_mode)
 		err = get_bootparam(&real_mode->orig_video_isVGA, offset, 1);
 		if (err)
 			goto out;
+	} else {
+		real_mode->orig_video_isVGA = 0;
+		close(fd);
+		return 0;
 	}
 	close(fd);
 
@@ -844,7 +848,7 @@ void setup_linux_system_parameters(struct kexec_info *info,
 	setup_subarch(real_mode);
 	if (bzImage_support_efi_boot && !arch_options.noefi)
 		setup_efi_info(info, real_mode);
-	
+
 	/* Default screen size */
 	real_mode->orig_x = 0;
 	real_mode->orig_y = 0;