From c350eee33b7a95dc1ff690be8a99af2caf2722de Mon Sep 17 00:00:00 2001
From: Noah Gold <nkgold@google.com>
Date: Fri, 19 May 2023 11:44:33 -0700
Subject: [PATCH] hypervisor: implement blanket MSR fetch for WHPX.

For snapshotting, we want to save/restore *all* MSRs rather
than a one or two specific MSRs. To accomplish this, we're
implementing get_all_msrs for WHPX.

BUG=b:269705560
TEST=unit tests

Change-Id: I706c3bd1d9d11ca58c709e1a19e0184dc560f193
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4546271
Commit-Queue: Noah Gold <nkgold@google.com>
Reviewed-by: Richard Zhang <rizhang@google.com>
Reviewed-by: Frederick Mayle <fmayle@google.com>
---
 hypervisor/src/whpx/vcpu.rs | 60 +++++++++++++++++++++++++++++++++++--
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/hypervisor/src/whpx/vcpu.rs b/hypervisor/src/whpx/vcpu.rs
index 61c27e9af8..738e86a13c 100644
--- a/hypervisor/src/whpx/vcpu.rs
+++ b/hypervisor/src/whpx/vcpu.rs
@@ -14,7 +14,6 @@ use libc::EINVAL;
 use libc::EIO;
 use libc::ENOENT;
 use libc::ENXIO;
-use libc::EOPNOTSUPP;
 use vm_memory::GuestAddress;
 use winapi::shared::winerror::E_UNEXPECTED;
 use windows::Win32::Foundation::WHV_E_INSUFFICIENT_BUFFER;
@@ -1157,9 +1156,64 @@ impl VcpuX86_64 for WhpxVcpu {
         Ok(())
     }
 
-    // TODO: b/270734340 implement
     fn get_all_msrs(&self) -> Result<Vec<Register>> {
-        Err(Error::new(EOPNOTSUPP))
+        // Note that some members of VALID_MSRS cannot be fetched from WHPX with
+        // WHvGetVirtualProcessorRegisters per the HTLFS, so we enumerate all of
+        // permitted MSRs here.
+        //
+        // We intentionally exclude WHvRegisterPendingInterruption and
+        // WHvRegisterInterruptState because they are included in
+        // get_interrupt_state.
+        //
+        // We also exclude MSR_TSC, because on WHPX, we will use virtio-pvclock
+        // to restore the guest clocks. Note that this will be *guest aware*
+        // snapshotting. We may in the future add guest unaware snapshotting
+        // for Windows, in which case we will want to save/restore TSC such that
+        // the guest does not observe any change.
+        let mut registers = vec![
+            Register {
+                id: MSR_EFER,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_KERNEL_GS_BASE,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_APIC_BASE,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_SYSENTER_CS,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_SYSENTER_EIP,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_SYSENTER_ESP,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_STAR,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_LSTAR,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_CSTAR,
+                ..Default::default()
+            },
+            Register {
+                id: MSR_SFMASK,
+                ..Default::default()
+            },
+        ];
+        self.get_msrs(&mut registers)?;
+        Ok(registers)
     }
 
     /// Sets the model-specific registers.