[v1] TDX support

[RFC PATCH 09/23] target/i386: kvm: don't synchronize guest tsc for TD guest

Isaku Yamahata posted 23 patches 4 years, 9 months ago

Diff against v2
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Maintainers: "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Alistair Francis <alistair@alistair23.me>, Eduardo Habkost <ehabkost@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Cornelia Huck <cohuck@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>

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[RFC PATCH 09/23] target/i386: kvm: don't synchronize guest tsc for TD guest

Posted by Isaku Yamahata 4 years, 9 months ago

Make kvm_synchronize_all_tsc() nop for TD-guest.

TDX module specification, 9.11.1 TSC Virtualization
"Virtual TSC values are consistent among all the TD;s VCPUs at the
level suppored by the CPU".
There is no need for qemu to synchronize tsc and VMM can't access
to guest TSC. Actually do_kvm_synchronize_tsc() hits assert due to
failure to write to guest tsc.

> qemu/target/i386/kvm.c:235: kvm_get_tsc: Assertion `ret == 1' failed.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 target/i386/kvm/kvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index fb94cdd370..beb768a7d3 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -247,7 +247,7 @@ void kvm_synchronize_all_tsc(void)
 {
     CPUState *cpu;
 
-    if (kvm_enabled()) {
+    if (kvm_enabled() && vm_type != KVM_X86_TDX_VM) {
         CPU_FOREACH(cpu) {
             run_on_cpu(cpu, do_kvm_synchronize_tsc, RUN_ON_CPU_NULL);
         }
-- 
2.17.1