Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS | Date | Mon, 09 Mar 2020 10:09:00 +0100 |
| |
Paolo Bonzini <pbonzini@redhat.com> writes: > On 09/03/20 07:57, Thomas Gleixner wrote: >> Thomas Gleixner <tglx@linutronix.de> writes: >> >> guest side: >> >> nmi()/mce() ... >> >> stash_crs(); >> >> + stash_and_clear_apf_reason(); >> >> .... >> >> + restore_apf_reason(); >> >> restore_cr2(); >> >> Too obvious, isn't it? > > Yes, this works but Andy was not happy about adding more > save-and-restore to NMIs. If you do not want to do that, I'm okay with > disabling async page fault support for now.
I'm fine with doing that save/restore dance, but I have no strong opinion either.
> Storing the page fault reason in memory was not a good idea. Better > options would be to co-opt the page fault error code (e.g. store the > reason in bits 31:16, mark bits 15:0 with the invalid error code > RSVD=1/P=0), or to use the virtualization exception area.
Memory store is not the problem. The real problem is hijacking #PF.
If you'd have just used a separate VECTOR_ASYNC_PF then none of these problems would exist at all.
Thanks,
tglx
| |