Re: [PATCH 1/4] Prep for paravirt: Be careful about touching BIOS address space

(Andrew had already taken that last one, I meant to send this)

Subject: Be careful about touching BIOS address space

BIOS ROM areas may not be mapped into the guest address space, so be careful
when touching those addresses to make sure they appear to be mapped.

Signed-off-by: Jeremy Fitzhardinge <redacted>
Signed-off-by: Rusty Russell <redacted>

===================================================================

--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c

@@ -270,7 +270,14 @@ static struct resource standard_io_resou
 	.flags	= IORESOURCE_BUSY | IORESOURCE_IO
 } };
 
-#define romsignature(x) (*(unsigned short *)(x) == 0xaa55)
+static inline int romsignature(const unsigned char *x)
+{
+     unsigned short sig;
+     int ret = 0;
+     if (__get_user(sig, (const unsigned short *)x) == 0)
+	  ret = (sig == 0xaa55);