From fdcf7a9316cacf059b09558700a8be71fdc094fe Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 22 Jun 2012 10:04:30 +0200 Subject: [PATCH] x86/PCI: fix guest_io_read() when pci_cfg_ok() denies access For a multi-byte aligned read, this so far resulted in 0x00ff to be put in the guest's register rather than 0xffff or 0xffffffff, which in turn could confuse bus scanning functions (which, when reading vendor and/or device IDs, expect to get back all zeroes or all ones). As the value gets masked to the read width when merging back into the full result, setting the initial value to all ones should not harm any or the other cases. Signed-off-by: Jan Beulich Acked-by: Keir Fraser --- xen/arch/x86/traps.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index 2264583f14..dc80c6f506 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -1717,7 +1717,7 @@ static uint32_t guest_io_read( while ( bytes != 0 ) { unsigned int size = 1; - uint32_t sub_data = 0xff; + uint32_t sub_data = ~0; if ( (port == 0x42) || (port == 0x43) || (port == 0x61) ) { -- 2.30.2