usb-host: add option to allow all resets.

[thirdparty/qemu.git] / docs / hyperv.txt

diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index 8fdf25c8291c90ee71c53867628827aeb867ad77..6518b716a9585c995a7beb21c87384b33eb71390 100644 (file)
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -184,6 +184,19 @@ enabled.
 
 Requires: hv-vpindex, hv-synic, hv-time, hv-stimer
 
+3.17. hv-no-nonarch-coresharing=on/off/auto
+===========================================
+This enlightenment tells guest OS that virtual processors will never share a
+physical core unless they are reported as sibling SMT threads. This information
+is required by Windows and Hyper-V guests to properly mitigate SMT related CPU
+vulnerabilities.
+When the option is set to 'auto' QEMU will enable the feature only when KVM
+reports that non-architectural coresharing is impossible, this means that
+hyper-threading is not supported or completely disabled on the host. This
+setting also prevents migration as SMT settings on the destination may differ.
+When the option is set to 'on' QEMU will always enable the feature, regardless
+of host setup. To keep guests secure, this can only be used in conjunction with
+exposing correct vCPU topology and vCPU pinning.
 
 4. Development features
 ========================