From f4129197034594568cde7f1a372b889ca8962e45 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pierre-Cl=C3=A9ment=20Tosi?= <ptosi@google.com>
Date: Thu, 14 Jul 2022 09:51:49 +0100
Subject: [PATCH] hypervisor: kvm: aarch64: Support any KVM_GET_ONE_REG target
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Re-work the API to support non-64-bit registers (e.g. FP & SIMD), as
supported by the architecture and KVM and keep *_u64 helpers for the
common case of 64-bit registers.

Note: no functional change intended.

BUG=b:222222882
BUG=chromium:1141812
TEST=tools/dev_container ./tools/run_tests

Change-Id: I9dd95e96ba4b1f759c603f885ff38aefab52b5cc
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3780661
Auto-Submit: Pierre-Clément Tosi <ptosi@google.com>
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Tested-by: Pierre-Clément Tosi <ptosi@google.com>
Commit-Queue: Pierre-Clément Tosi <ptosi@google.com>
---
 hypervisor/src/kvm/aarch64.rs | 36 +++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/hypervisor/src/kvm/aarch64.rs b/hypervisor/src/kvm/aarch64.rs
index e5b485e31b..ef3156282c 100644
--- a/hypervisor/src/kvm/aarch64.rs
+++ b/hypervisor/src/kvm/aarch64.rs
@@ -232,11 +232,16 @@ impl KvmVcpu {
         Ok(VcpuExit::SystemEventReset)
     }
 
-    fn set_one_kvm_reg(&self, kvm_reg_id: KvmVcpuRegister, data: u64) -> Result<()> {
-        let data_ref = &data as *const u64;
+    fn set_one_kvm_reg_u64(&self, kvm_reg_id: KvmVcpuRegister, data: u64) -> Result<()> {
+        self.set_one_kvm_reg(kvm_reg_id, data.to_ne_bytes().as_slice())
+    }
+
+    fn set_one_kvm_reg(&self, kvm_reg_id: KvmVcpuRegister, data: &[u8]) -> Result<()> {
         let onereg = kvm_one_reg {
             id: kvm_reg_id.0,
-            addr: data_ref as u64,
+            addr: (data.as_ptr() as usize)
+                .try_into()
+                .expect("can't represent usize as u64"),
         };
         // Safe because we allocated the struct and we know the kernel will read exactly the size of
         // the struct.
@@ -248,20 +253,27 @@ impl KvmVcpu {
         }
     }
 
-    fn get_one_kvm_reg(&self, kvm_reg_id: KvmVcpuRegister) -> Result<u64> {
-        let mut val: u64 = 0;
+    fn get_one_kvm_reg_u64(&self, kvm_reg_id: KvmVcpuRegister) -> Result<u64> {
+        let mut bytes = 0u64.to_ne_bytes();
+        self.get_one_kvm_reg(kvm_reg_id, bytes.as_mut_slice())?;
+        Ok(u64::from_ne_bytes(bytes))
+    }
+
+    fn get_one_kvm_reg(&self, kvm_reg_id: KvmVcpuRegister, data: &mut [u8]) -> Result<()> {
         let onereg = kvm_one_reg {
             id: kvm_reg_id.0,
-            addr: (&mut val as *mut u64) as u64,
+            addr: (data.as_mut_ptr() as usize)
+                .try_into()
+                .expect("can't represent usize as u64"),
         };
 
         // Safe because we allocated the struct and we know the kernel will read exactly the size of
         // the struct.
         let ret = unsafe { ioctl_with_ref(self, KVM_GET_ONE_REG(), &onereg) };
         if ret == 0 {
-            Ok(val)
+            Ok(())
         } else {
-            return errno_result();
+            errno_result()
         }
     }
 }
@@ -435,20 +447,20 @@ impl VcpuAArch64 for KvmVcpu {
     }
 
     fn set_one_reg(&self, reg_id: VcpuRegAArch64, data: u64) -> Result<()> {
-        self.set_one_kvm_reg(KvmVcpuRegister::from(reg_id), data)
+        self.set_one_kvm_reg_u64(KvmVcpuRegister::from(reg_id), data)
     }
 
     fn get_one_reg(&self, reg_id: VcpuRegAArch64) -> Result<u64> {
-        self.get_one_kvm_reg(KvmVcpuRegister::from(reg_id))
+        self.get_one_kvm_reg_u64(KvmVcpuRegister::from(reg_id))
     }
 
     fn get_psci_version(&self) -> Result<PsciVersion> {
         // The definition of KVM_REG_ARM_PSCI_VERSION is in arch/arm64/include/uapi/asm/kvm.h.
         const KVM_REG_ARM_PSCI_VERSION: u64 =
             KVM_REG_ARM64 | (KVM_REG_SIZE_U64 as u64) | (KVM_REG_ARM_FW as u64);
+        const PSCI_VERSION: KvmVcpuRegister = KvmVcpuRegister(KVM_REG_ARM_PSCI_VERSION);
 
-        let version = if let Ok(v) = self.get_one_kvm_reg(KvmVcpuRegister(KVM_REG_ARM_PSCI_VERSION))
-        {
+        let version = if let Ok(v) = self.get_one_kvm_reg_u64(PSCI_VERSION) {
             let v = u32::try_from(v).map_err(|_| Error::new(EINVAL))?;
             PsciVersion::try_from(v)?
         } else {