On Tue, Mar 05, 2019 at 09:34:13PM +0800, Kairui Song wrote: > On Tue, Mar 5, 2019 at 8:33 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > On Tue, Mar 05, 2019 at 08:17:03PM +0800, Kairui Song wrote: > > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > > > index 7abb09e2eeb8..34aa1e953dfc 100644 > > > --- a/arch/x86/hyperv/hv_init.c > > > +++ b/arch/x86/hyperv/hv_init.c > > > @@ -406,6 +406,12 @@ void hyperv_cleanup(void) > > > /* Reset our OS id */ > > > wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0); > > > > > > + /* Cleanup hypercall page reference before reset the page */ > > > + hv_hypercall_pg = NULL; > > > + > > > + /* Make sure page reference is cleared before wrmsr */ > > > > This comment forgets to tell us who cares about this. And why the wrmsr > > itself isn't serializing enough. > > > > > + wmb(); > > > + > > > /* Reset the hypercall page */ > > > hypercall_msr.as_uint64 = 0; > > > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > > > That looks like a fake MSR; and you're telling me that VMEXIT doesn't > > serialize? > > Thanks for the review, seem I being a bit paranoid on this. Will drop > it and send a v3 if no one has any other complaint. Also; our wrmsr implementation has a "memory" clobber on, which means you don't even need a compiler barrier to force emit that store before the wrmsr. You might want to retain the comment that explains this ordering though. hv_hypercall_pg = NULL; /* * text that explains why hv_hypercall_pg must be set NULL * before the wrmsr */ wrmsrl(...); _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
