On Thu, Jun 01, 2023 at 10:56:03AM +0200, Peter Zijlstra wrote: > On Thu, Jun 01, 2023 at 01:45:35PM +0500, Muhammad Usama Anjum wrote: > > Hi, > > > > I've been looking into a problem where Windows applications misbehave > > across suspend/resume when run on Wine on x86. These applications see time > > going backwards. The timestamp counter (TSC) is reset when system resumes. > > In case of Windows on Intel and AMD, the timestamp is saved and restored > > when the system resumes from suspend. > > > > These applications read timestamp by rdtsc directly. These calls cannot be > > intercepted by Wine. The application should be fixed such that it handles > > these scenarios correctly. But there are hundreds of applications which > > cannot be fixed. So some support is required in Wine or kernel. There isn't > > anything which Wine can do as rdtsc call directly reads the timestamp. The > > only option is that we support something in kernel. > > > > As more and more things are being added to Wine, Windows application can be > > run pretty easily on Linux. But this rdtsc is a big hurdle. What are your > > thoughts on solving this problem? > > > > We are thinking of saving and restoring the timestamp counter at suspend > > and resume time respectively. In theory it can work on Intel because of > > TSC_ADJUST register. But it'll never work on AMD until: > > * AMD supports the same kind of adjust register. (AMD has said that the > > adjust register cannot be implemented in their firmware. They'll have to > > add it to their hardware.) > > * by manual synchronization in kernel (I know you don't like this idea. But > > there is something Windows is doing to save/restore and sync the TSC) > > Wine could set TIF_NOTSC, which will cause it to run with CR4.TSD > cleared and cause RDTSC to #GP, at which point you can emulate it. The other option is to have Wine run itself in a (KVM) virtual machine and mess with the VMM TSC offset :-)
