On Thu, Nov 17, 2022 at 12:23:50AM +0000, Sean Christopherson wrote: > Automatically disable single-step when the guest reaches the end of the > verified section instead of using an explicit ucall() to ask userspace to > disable single-step. An upcoming change to implement a pool-based scheme > for ucall() will add an atomic operation (bit test and set) in the guest > ucall code, and if the compiler generate "old school" atomics, e.g. Off topic, but I didn't ask when we were discussing this issue. What is the atomic used for in the pool-based ucall implementation? > 40e57c: c85f7c20 ldxr x0, [x1] > 40e580: aa100011 orr x17, x0, x16 > 40e584: c80ffc31 stlxr w15, x17, [x1] > 40e588: 35ffffaf cbnz w15, 40e57c <__aarch64_ldset8_sync+0x1c> > > the guest will hang as the local exclusive monitor is reset by eret, > i.e. the stlxr will always fail due to the VM-Exit for the debug > exception. ... due to the debug exception taken to EL2. What's a VM-Exit anyways? ;-) > Link: https://lore.kernel.org/all/20221006003409.649993-8-seanjc@xxxxxxxxxx > Cc: Oliver Upton <oliver.upton@xxxxxxxxx> > Cc: Marc Zyngier <maz@xxxxxxxxxx> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> With the commit message nit: Reviewed-by: Oliver Upton <oliver.upton@xxxxxxxxx> -- Thanks, Oliver _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
