On Tue, Apr 23, 2019 at 03:15:37PM +0200, Vitaly Kuznetsov wrote: > It was reported that with some special Multi Processor Group configuration, > e.g: > bcdedit.exe /set groupsize 1 > bcdedit.exe /set maxgroup on > bcdedit.exe /set groupaware on > for a 16-vCPU guest WS2012 shows BSOD on boot when PV TLB flush mechanism > is in use. > > Tracing kvm_hv_flush_tlb immediately reveals the issue: > > kvm_hv_flush_tlb: processor_mask 0x0 address_space 0x0 flags 0x2 > > The only flag set in this request is HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES, > however, processor_mask is 0x0 and no HV_FLUSH_ALL_PROCESSORS is specified. > We don't flush anything and apparently it's not what Windows expects. > > TLFS doesn't say anything about such requests and newer Windows versions > seem to be unaffected. This all feels like a WS2012 bug, which is, however, > easy to workaround in KVM: let's flush everything when we see an empty > flush request, over-flushing doesn't hurt. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > --- Reviewed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
