Messages in this thread | | | Date | Fri, 3 Apr 2020 18:42:44 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH] x86/split_lock: Disable SLD if an unaware (out-of-tree) module enables VMX |
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On Fri, Apr 03, 2020 at 09:30:07AM -0700, Sean Christopherson wrote: > Hook into native CR4 writes to disable split-lock detection if CR4.VMXE > is toggled on by an SDL-unaware entity, e.g. an out-of-tree hypervisor > module. Most/all VMX-based hypervisors blindly reflect #AC exceptions > into the guest, or don't intercept #AC in the first place. With SLD > enabled, this results in unexpected #AC faults in the guest, leading to > crashes in the guest and other undesirable behavior. > > Reported-by: "Kenneth R. Crudup" <kenny@panix.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Jessica Yu <jeyu@kernel.org> > Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk> > Cc: Kenneth R. Crudup <kenny@panix.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Fenghua Yu <fenghua.yu@intel.com> > Cc: Xiaoyao Li <xiaoyao.li@intel.com> > Cc: Nadav Amit <namit@vmware.com> > Cc: Thomas Hellstrom <thellstrom@vmware.com> > Cc: Tony Luck <tony.luck@intel.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Jann Horn <jannh@google.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: David Laight <David.Laight@ACULAB.COM> > Cc: Doug Covelli <dcovelli@vmware.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > > A bit ugly, but on the plus side the code is largely contained to intel.c. > I think forgoing the on_all_cpus() remote kill is safe?
How would it be safe? You can't control where the module text will be ran, or how quickly.
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