cpu/vc Add #VC handler tests

Adds tests that make sure a #VC exception is raised while executing
various instructions and that the #VC handler properly handles them via
the ghcb.

Adds tests for cpuid, msrs, port IO, MMIO, wbinvd, rdtsc, dr7, and vmmcall.

Relies on being able to run tests inside the guest VM, e.g. with PR coconut-svsm#120.

The #VC handler is not yet implemented, so these tests are all marked
with #[should_panic]. See PR coconut-svsm#55 for progress on its implementation.

TODO:
Remove added dependencies
Move the tests to vc.rs or a new file
Clean up comments, etc.
Move assembly wrapper helper functions to more sensible places
Implement page state change (PSC) test

Signed-off-by: Adam Dunlap <acdunlap@google.com>

Cargo.toml

@@ -24,6 +24,8 @@ gdbstub_arch = { version = "0.2.4", optional = true }
 intrusive-collections = "0.9.6"
 log = { version = "0.4.17", features = ["max_level_info", "release_max_level_info"] }
 packit = { git = "https://github.com/coconut-svsm/packit", version = "0.1.0" }
+x86 = "0.52.0"
+raw-cpuid = "11.0"
 
 [target."x86_64-unknown-none".dev-dependencies]
 test = { version = "0.1.0", path = "test" }

src/cpu/msr.rs

@@ -51,6 +51,29 @@ pub fn rdtsc() -> u64 {
     (eax as u64) | (edx as u64) << 32
 }
 
+pub struct RdtscpOut {
+    pub timestamp: u64,
+    pub pid: u32,
+}
+
+pub fn rdtscp() -> RdtscpOut {
+    let eax: u32;
+    let edx: u32;
+    let ecx: u32;
+
+    unsafe {
+        asm!("rdtsc",
+             out("eax") eax,
+             out("ecx") ecx,
+             out("edx") edx,
+             options(att_syntax, nomem, nostack));
+    }
+    RdtscpOut {
+        timestamp: (eax as u64) | (edx as u64) << 32,
+        pid: ecx,
+    }
+}
+
 pub fn read_flags() -> u64 {
     let rax: u64;
     unsafe {