[xen master] cmdline: only set ask mode if vga= is present

[patchbot@xxxxxxx]

commit b831326ee2f9ed94523b3d8b0fb2da2a82113e9e
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Jul 10 18:35:09 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jul 10 18:35:09 2023 +0200

    cmdline: only set ask mode if vga= is present
    
    Commit 9473d9a24182 set the ASK mode without checking if there was a
    `vga` option provided in the command line.  This breaks existing
    behavior, so exit early without changes if `vga` is not present in the
    command line.
    
    Fixes: 9473d9a24182 ('cmdline: parse multiple instances of the vga option')
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/boot/cmdline.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/boot/cmdline.c b/xen/arch/x86/boot/cmdline.c
index 10dcc6142c..74997703b3 100644
--- a/xen/arch/x86/boot/cmdline.c
+++ b/xen/arch/x86/boot/cmdline.c
@@ -279,9 +279,13 @@ static void vga_parse(const char *cmdline, 
early_boot_opts_t *ebo)
 {
     const char *c = cmdline;
 
+    c = find_opt(c, "vga=", true);
+    if ( !c )
+        return;
+
     ebo->boot_vid_mode = ASK_VGA;
 
-    while ( (c = find_opt(c, "vga=", true)) != NULL )
+    do
     {
         unsigned int tmp, vesa_depth, vesa_height, vesa_width;
 
@@ -332,6 +336,7 @@ static void vga_parse(const char *cmdline, 
early_boot_opts_t *ebo)
         else if ( !strmaxcmp(c, "ask", delim_chars_comma) )
             ebo->boot_vid_mode = ASK_VGA;
     }
+    while ( (c = find_opt(c, "vga=", true)) != NULL );
 }
 #endif
 
--
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