[PATCH][RFC] gfx_passthru: warning when vgabios rom has invalid checksum

[Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>]

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Hi,

According to the "PCI Firmware Spec Rev 3.0",
the system firmware have to write the new checksum after resizing
the expansion ROM area.

So, when re-using the shadowed VGABIOS, the checksum must
be valid, and if it is invalid, we should consider the BIOS has
a bug or memory area is corrupted.

This patch just add the warning message when checksum requires
recalculation.

I tried this following environments.

Intel DX58SO + GeForce GTS250:	checksum is OK.
Intel DX58SO + GeForce 9600GT:	checksum is OK.
Fujitsu Q35 M/B + IGD:		checksum is bad.

What do you think, Weidong?
Is just warning enough? Or, should we stop loading the rom?

Regards,
Noboru.

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diff --git a/hw/pass-through.c b/hw/pass-through.c
index ecb3d6f..fadd358 100644
--- a/hw/pass-through.c
+++ b/hw/pass-through.c
@@ -4262,7 +4262,10 @@ static int setup_vga_pt(void)
     for ( c = (char*)bios; c < ((char*)bios + bios_size); c++ )
         checksum += *c;
     if ( checksum )
+    {
         bios[bios_size - 1] -= checksum;
+        PT_LOG("vga bios checksum is adjusted!\n");
+    }
 
     cpu_physical_memory_rw(0xc0000, bios, bios_size, 1);
 

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