On Fri, Nov 17, 2023 at 11:17:46AM +0100, Roger Pau Monné wrote: > On Fri, Nov 17, 2023 at 09:18:39AM +0000, James Dingwall wrote: > > On Thu, Nov 16, 2023 at 04:32:47PM +0000, Andrew Cooper wrote: > > > On 16/11/2023 4:15 pm, James Dingwall wrote: > > > > Hi, > > > > > > > > Per the msr_relaxed documentation: > > > > > > > > "If using this option is necessary to fix an issue, please report a > > > > bug." > > > > > > > > After recently upgrading an environment from Xen 4.14.5 to Xen 4.15.5 we > > > > started experiencing a BSOD at boot with one of our Windows guests. We > > > > found > > > > that enabling `msr_relaxed = 1` in the guest configuration has resolved > > > > the > > > > problem. With a debug build of Xen and `hvm_debug=2048` on the command > > > > line > > > > the following messages were caught as the BSOD happened: > > > > > > > > (XEN) [HVM:11.0] <vmx_msr_read_intercept> ecx=0x1a2 > > > > (XEN) vmx.c:3298:d11v0 RDMSR 0x000001a2 unimplemented > > > > (XEN) d11v0 VIRIDIAN CRASH: 1e ffffffffc0000096 fffff80b8de81eb5 0 0 > > > > > > > > I found that MSR 0x1a2 is MSR_TEMPERATURE_TARGET and from that this > > > > patch > > > > series from last month: > > > > > > > > https://patchwork.kernel.org/project/xen-devel/list/?series=796550 > > > > > > > > Picking out just a small part of that fixes the problem for us. > > > > Although the > > > > the patch is against 4.15.5 I think it would be relevant to more recent > > > > releases too. > > > > > > Which version of Windows, and what hardware? > > > > > > The Viridian Crash isn't about the RDMSR itself - it's presumably > > > collateral damage shortly thereafter. > > > > > > Does filling in 0 for that MSR also resolve the issue? It's model > > > specific and we absolutely cannot pass it through from real hardware > > > like that. > > > > > > > Hi Andrew, > > > > Thanks for your response. The guest is running Windows 10 and the crash > > happens in a proprietary hardware driver. > > When you say proprietary you mean a custom driver made for your > use-case, or is this some vendor driver widely available? >
Hi Roger, We have emulated some point of sale hardware with a custom qemu device. It is reasonably common but limited to its particular sector. As the physical hardware is all built to the same specification I assume the driver has made assumptions about the availability of MSR_TEMPERATURE_TARGET and doesn't handle the case it is absent which leads to the BSOD in the Windows guest. Regards, James
