[PATCH] x86emul: support RDPKRU/WRPKRU

[Jan Beulich <jbeulich@xxxxxxxx>]

Since we support PKU for HVM guests, the respective insns should also be
recognized by the emulator.

In emul_test_read_cr() instead of further extending the comment to
explain the hex numbers, switch to using X86_CR4_* values.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -2399,6 +2399,23 @@ int main(int argc, char **argv)
         goto fail;
     printf("okay\n");
 
+    printf("%-40s", "Testing rdpkru / wrpkru...");
+    instr[0] = 0x0f; instr[1] = 0x01;
+    regs.ecx = 0;
+    for ( i = 0, j = (uint32_t)-__LINE__; i < 3; ++i )
+    {
+        instr[2] = 0xee | (i & 1);
+        regs.eax = i < 2 ? j : 0;
+        regs.edx = i & 1 ? 0 : j;
+        regs.eip = (unsigned long)&instr[0];
+        rc = x86_emulate(&ctxt, &emulops);
+        if ( (rc != X86EMUL_OKAY) ||
+             (!(i & 1) && (regs.eax != (i ? j : 0) || regs.edx)) ||
+             (regs.eip != (unsigned long)&instr[3]) )
+            goto fail;
+    }
+    printf("okay\n");
+
     printf("%-40s", "Testing movdiri %edx,(%ecx)...");
     if ( stack_exec && cpu_has_movdiri )
     {
--- a/tools/tests/x86_emulator/x86-emulate.c
+++ b/tools/tests/x86_emulator/x86-emulate.c
@@ -184,8 +184,8 @@ int emul_test_read_cr(
         return X86EMUL_OKAY;
 
     case 4:
-        /* OSFXSR, OSXMMEXCPT, and maybe OSXSAVE */
-        *val = 0x00000600 | (cpu_has_xsave ? 0x00040000 : 0);
+        *val = X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT | X86_CR4_PKE |
+               (cpu_has_xsave ? X86_CR4_OSXSAVE : 0);
         return X86EMUL_OKAY;
     }
 
@@ -256,4 +256,16 @@ void emul_test_put_fpu(
     /* TBD */
 }
 
+static uint32_t pkru;
+
+static unsigned int read_pkru(void)
+{
+    return pkru;
+}
+
+static void write_pkru(unsigned int val)
+{
+    pkru = val;
+}
+
 #include "x86_emulate/x86_emulate.c"
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -5815,6 +5815,39 @@ x86_emulate(
             }
             break;
 
+        case 0xee:
+            switch ( vex.pfx )
+            {
+            case vex_none: /* rdpkru */
+                if ( !ops->read_cr ||
+                     ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY )
+                    cr4 = 0;
+                generate_exception_if(!(cr4 & X86_CR4_PKE), EXC_UD);
+                generate_exception_if(_regs.ecx, EXC_GP, 0);
+                _regs.r(ax) = read_pkru();
+                _regs.r(dx) = 0;
+                break;
+            default:
+                goto unimplemented_insn;
+            }
+            break;
+
+        case 0xef:
+            switch ( vex.pfx )
+            {
+            case vex_none: /* wrpkru */
+                if ( !ops->read_cr ||
+                     ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY )
+                    cr4 = 0;
+                generate_exception_if(!(cr4 & X86_CR4_PKE), EXC_UD);
+                generate_exception_if(_regs.ecx | _regs.edx, EXC_GP, 0);
+                write_pkru(_regs.eax);
+                break;
+            default:
+                goto unimplemented_insn;
+            }
+            break;
+
         case 0xf8: /* swapgs */
             generate_exception_if(!mode_64bit(), EXC_UD);
             generate_exception_if(!mode_ring0(), EXC_GP, 0);
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -385,6 +385,17 @@ static inline unsigned int read_pkru(voi
     return pkru;
 }
 
+static inline void write_pkru(unsigned int pkru)
+{
+    unsigned long cr4 = read_cr4();
+
+    /* See read_pkru() */
+    write_cr4(cr4 | X86_CR4_PKE);
+    asm volatile ( ".byte 0x0f, 0x01, 0xef"
+                   :: "a" (pkru), "d" (0), "c" (0) );
+    write_cr4(cr4);
+}
+
 /* Macros for PKRU domain */
 #define PKRU_READ  (0)
 #define PKRU_WRITE (1)