Merge pull request #327 from 00xc/cpu/vc-rdtsc

cpu/vc: implement `RDTSC` and `RDSTCP` #VC handlers
coconut-svsm · Apr 26, 2024 · 95e2039 · 95e2039
2 parents a58ba53 + 447e578
commit 95e2039
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Showing 4 changed files with 188 additions and 143 deletions.
diff --git a/kernel/src/cpu/insn.rs b/kernel/src/cpu/insn.rs
@@ -60,6 +60,8 @@ pub enum DecodedInsn {
     Outw(Operand),
     Wrmsr,
     Rdmsr,
+    Rdtsc,
+    Rdtscp,
 }
 
 impl DecodedInsn {
@@ -79,6 +81,8 @@ impl DecodedInsn {
             Self::Outw(Operand::Imm(..)) => 3,
             Self::Outl(Operand::Imm(..)) => 2,
             Self::Wrmsr | Self::Rdmsr => 2,
+            Self::Rdtsc => 2,
+            Self::Rdtscp => 3,
         }
     }
 }
@@ -121,7 +125,13 @@ impl Instruction {
                 _ => (),
             },
             0x0F => match self.0[1] {
+                0x01 => {
+                    if self.0[2] == 0xf9 {
+                        return Ok(DecodedInsn::Rdtscp);
+                    }
+                }
                 0x30 => return Ok(DecodedInsn::Wrmsr),
+                0x31 => return Ok(DecodedInsn::Rdtsc),
                 0x32 => return Ok(DecodedInsn::Rdmsr),
                 0xA2 => return Ok(DecodedInsn::Cpuid),
                 _ => (),

diff --git a/kernel/src/cpu/msr.rs b/kernel/src/cpu/msr.rs
@@ -63,7 +63,7 @@ pub fn rdtscp() -> RdtscpOut {
     let ecx: u32;
 
     unsafe {
-        asm!("rdtsc",
+        asm!("rdtscp",
              out("eax") eax,
              out("ecx") ecx,
              out("edx") edx,

diff --git a/kernel/src/cpu/vc.rs b/kernel/src/cpu/vc.rs
@@ -21,9 +21,11 @@ use core::fmt;
 
 pub const SVM_EXIT_EXCP_BASE: usize = 0x40;
 pub const SVM_EXIT_LAST_EXCP: usize = 0x5f;
+pub const SVM_EXIT_RDTSC: usize = 0x6e;
 pub const SVM_EXIT_CPUID: usize = 0x72;
 pub const SVM_EXIT_IOIO: usize = 0x7b;
 pub const SVM_EXIT_MSR: usize = 0x7c;
+pub const SVM_EXIT_RDTSCP: usize = 0x87;
 pub const X86_TRAP_DB: usize = 0x01;
 pub const X86_TRAP: usize = SVM_EXIT_EXCP_BASE + X86_TRAP_DB;
 
@@ -97,9 +99,10 @@ pub fn stage2_handle_vc_exception_no_ghcb(ctx: &mut X86ExceptionContext) -> Resu
 pub fn stage2_handle_vc_exception(ctx: &mut X86ExceptionContext) -> Result<(), SvsmError> {
     let err = ctx.error_code;
 
-    // To handle NAE events, we're supposed to reset the VALID_BITMAP field of the GHCB.
-    // This is currently only relevant for IOIO handling. This field is currently reset in
-    // the ioio_{in,ou} methods but it would be better to move the reset out of the different
+    // To handle NAE events, we're supposed to reset the VALID_BITMAP field of
+    // the GHCB. This is currently only relevant for IOIO, RDTSC and RDTSCP
+    // handling. This field is currently reset in the relevant GHCB methods
+    // but it would be better to move the reset out of the different
     // handlers.
     let mut ghcb = current_ghcb();
 
@@ -109,6 +112,8 @@ pub fn stage2_handle_vc_exception(ctx: &mut X86ExceptionContext) -> Result<(), S
         (SVM_EXIT_CPUID, Some(DecodedInsn::Cpuid)) => handle_cpuid(ctx),
         (SVM_EXIT_IOIO, Some(ins)) => handle_ioio(ctx, &mut ghcb, ins),
         (SVM_EXIT_MSR, Some(ins)) => handle_msr(ctx, &mut ghcb, ins),
+        (SVM_EXIT_RDTSC, Some(DecodedInsn::Rdtsc)) => ghcb.rdtsc_regs(&mut ctx.regs),
+        (SVM_EXIT_RDTSCP, Some(DecodedInsn::Rdtsc)) => ghcb.rdtscp_regs(&mut ctx.regs),
         _ => Err(VcError::new(ctx, VcErrorType::Unsupported).into()),
     }?;
 
@@ -119,9 +124,10 @@ pub fn stage2_handle_vc_exception(ctx: &mut X86ExceptionContext) -> Result<(), S
 pub fn handle_vc_exception(ctx: &mut X86ExceptionContext) -> Result<(), SvsmError> {
     let error_code = ctx.error_code;
 
-    // To handle NAE events, we're supposed to reset the VALID_BITMAP field of the GHCB.
-    // This is currently only relevant for IOIO handling. This field is currently reset in
-    // the ioio_{in,ou} methods but it would be better to move the reset out of the different
+    // To handle NAE events, we're supposed to reset the VALID_BITMAP field of
+    // the GHCB. This is currently only relevant for IOIO, RDTSC and RDTSCP
+    // handling. This field is currently reset in the relevant GHCB methods
+    // but it would be better to move the reset out of the different
     // handlers.
     let mut ghcb = current_ghcb();
 
@@ -138,6 +144,8 @@ pub fn handle_vc_exception(ctx: &mut X86ExceptionContext) -> Result<(), SvsmErro
         (SVM_EXIT_CPUID, Some(DecodedInsn::Cpuid)) => handle_cpuid(ctx),
         (SVM_EXIT_IOIO, Some(ins)) => handle_ioio(ctx, &mut ghcb, ins),
         (SVM_EXIT_MSR, Some(ins)) => handle_msr(ctx, &mut ghcb, ins),
+        (SVM_EXIT_RDTSC, Some(DecodedInsn::Rdtsc)) => ghcb.rdtsc_regs(&mut ctx.regs),
+        (SVM_EXIT_RDTSCP, Some(DecodedInsn::Rdtsc)) => ghcb.rdtscp_regs(&mut ctx.regs),
         _ => Err(VcError::new(ctx, VcErrorType::Unsupported).into()),
     }?;
 
@@ -584,8 +592,7 @@ mod tests {
     }
 
     #[test]
-    // #[cfg_attr(not(test_in_svsm), ignore = "Can only be run inside guest")]
-    #[ignore = "Currently unhandled by #VC handler"]
+    #[cfg_attr(not(test_in_svsm), ignore = "Can only be run inside guest")]
     fn test_rdtsc() {
         let mut prev: u64 = rdtsc();
         for _ in 0..50 {
@@ -596,8 +603,7 @@ mod tests {
     }
 
     #[test]
-    // #[cfg_attr(not(test_in_svsm), ignore = "Can only be run inside guest")]
-    #[ignore = "Currently unhandled by #VC handler"]
+    #[cfg_attr(not(test_in_svsm), ignore = "Can only be run inside guest")]
     fn test_rdtscp() {
         let expected_pid = u32::try_from(verify_ghcb_gets_altered(|| read_msr(MSR_TSC_AUX)))
             .expect("pid should be 32 bits");