[PATCH] cpu: msr: GPF avoidance on BOCHs QEMU systems (LP: #925001)

[Chris Van Hoof]

On 02/02/2012 05:46 AM, Colin King wrote:
> From: Colin Ian King<colin.king at canonical.com>
>
> Bochs firmware based QEMU systems on some configurations get
> General Protection Faults when running the MSR tests.  Since this
> isn't real hardware that we care about we can just kludge around
> this by not allowing the MSR tests in Bochs based systems.
>
> Signed-off-by: Colin Ian King<colin.king at canonical.com>
> ---
>   src/cpu/msr/msr.c |   19 +++++++++++++++++++
>   1 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/src/cpu/msr/msr.c b/src/cpu/msr/msr.c
> index d6aa00e..5de27a7 100644
> --- a/src/cpu/msr/msr.c
> +++ b/src/cpu/msr/msr.c
> @@ -30,6 +30,8 @@ static fwts_cpuinfo_x86 *cpuinfo;
>
>   static int msr_init(fwts_framework *fw)
>   {
> +	char *bios_vendor;
> +
>   	if ((cpuinfo = fwts_cpu_get_info(0)) == NULL) {
>   		fwts_log_error(fw, "Cannot get CPU info");
>   		return FWTS_ERROR;
> @@ -45,6 +47,23 @@ static int msr_init(fwts_framework *fw)
>   		fwts_log_error(fw, "Cannot detect the number of CPUs on this machine.");
>   		return FWTS_ABORTED;
>   	}
> +
> +	/*
> +	 * Running MSR tests inside virtual machines such as QEMU with some kernel/kvm
> +	 * combinations have been observed to cause GPFs.  We kludge around this by
> +	 * avoiding MSR tests for a Bochs BIOS based QEMU virtual machine.
> +	 */
> +	if ((bios_vendor = fwts_get("/sys/class/dmi/id/bios_vendor")) != NULL) {
> +		if (strstr(bios_vendor, "Bochs")) {
> +			fwts_log_error(fw,
> +				"MSR test being avoiding inside a virtual machine as "
> +				"this is known to cause General Protection Faults on "
> +				"some configurations.");
> +			free(bios_vendor);
> +			return FWTS_SKIP;
> +		}
> +		free(bios_vendor);
> +	}
>   	return FWTS_OK;
>   }
>

Put together a test build[0] of fwts-live based with kernel 3.2.0-14.23 
+ fwts version 0.24.17 + this patch patch[1]:

  * [0] -- 
http://hwe.ubuntu.com/fwts-live/test_images/fwts-live-oneiric-amd64-experimental-usb-hdd-20120204-0.img
  * [1] -- 
http://kernel.ubuntu.com/git?p=vanhoof/fwts.git;a=shortlog;h=refs/heads/kvm-msr-test
  * [1] -- https://launchpad.net/~vanhoof/+archive/fwts-sandbox/+packages

"""
$ sudo kvm -m 512 -hda 
fwts-live-oneiric-amd64-experimental-usb-hdd-20120204-0.img --vga vmware

[ while in kvm instance ]

$ dmesg | grep BOCHS
ACPI: RSDP 00000000000fd9a0 00014 (v00 BOCHS )

$ dpkg -l fwts
[...]
ii  fwts	0.24.17ubuntu1 Firmware Test Suite

$ sudo fwts msr
Running 1 tests. results appended to results.log
Test: MSR register tests
  Test skipped..
"""

Everything looks good on my end and the rest of the --batch tests 
continue as expected.  Thanks Colin!

--chris

Tested-by: Chris Van Hoof <vanhoof at canonical.com>