MIPS: KVM/locore.S: Relax noat

Now that the at register ($1) is no longer saved by
__kvm_mips_vcpu_run(), relax the noat assembler directive so that it
only applies around code where at is restored before entering guest, and
saved after exiting guest.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13209/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kvm/locore.S b/arch/mips/kvm/locore.S
index 3ea522e4954b0c15d38791dffb1cbb0e0cfb9fec..1f2167bc847d72b197f292c8bfa3b3a784ff1ce4 100644 (file)
--- a/arch/mips/kvm/locore.S
+++ b/arch/mips/kvm/locore.S
@@ -48,7 +48,6 @@
  * a1: vcpu
  */
        .set    noreorder
-       .set    noat
 
 FEXPORT(__kvm_mips_vcpu_run)
        /* k0/k1 not being used in host kernel context */
@@ -145,6 +144,7 @@ FEXPORT(__kvm_mips_load_asid)
        /* Disable RDHWR access */
        mtc0    zero, CP0_HWRENA
 
+       .set    noat
        /* Now load up the Guest Context from VCPU */
        LONG_L  $1, VCPU_R1(k1)
        LONG_L  $2, VCPU_R2(k1)
@@ -256,6 +256,8 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra)
        LONG_S  $30, VCPU_R30(k1)
        LONG_S  $31, VCPU_R31(k1)
 
+       .set at
+
        /* We need to save hi/lo and restore them on the way out */
        mfhi    t0
        LONG_S  t0, VCPU_HI(k1)
@@ -307,9 +309,7 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra)
        /* load up the host EBASE */
        mfc0    v0, CP0_STATUS
 
-       .set    at
        or      k0, v0, ST0_BEV
-       .set    noat
 
        mtc0    k0, CP0_STATUS
        ehb
@@ -321,7 +321,6 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra)
         * If FPU is enabled, save FCR31 and clear it so that later ctc1's don't
         * trigger FPE for pending exceptions.
         */
-       .set    at
        and     v1, v0, ST0_CU1
        beqz    v1, 1f
         nop
@@ -331,7 +330,6 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra)
        sw      t0, VCPU_FCR31(k1)
        ctc1    zero,fcr31
        .set    pop
-       .set    noat
 1:
 
 #ifdef CONFIG_CPU_HAS_MSA
@@ -354,10 +352,8 @@ NESTED (MIPSX(GuestException), CALLFRAME_SIZ, ra)
 #endif
 
        /* Now that the new EBASE has been loaded, unset BEV and KSU_USER */
-       .set    at
        and     v0, v0, ~(ST0_EXL | KSU_USER | ST0_IE)
        or      v0, v0, ST0_CU0
-       .set    noat
        mtc0    v0, CP0_STATUS
        ehb
 
@@ -424,18 +420,14 @@ __kvm_mips_return_to_guest:
 
        /* Switch EBASE back to the one used by KVM */
        mfc0    v1, CP0_STATUS
-       .set    at
        or      k0, v1, ST0_BEV
-       .set    noat
        mtc0    k0, CP0_STATUS
        ehb
        mtc0    t0, CP0_EBASE
 
        /* Setup status register for running guest in UM */
-       .set    at
        or      v1, v1, (ST0_EXL | KSU_USER | ST0_IE)
        and     v1, v1, ~(ST0_CU0 | ST0_MX)
-       .set    noat
        mtc0    v1, CP0_STATUS
        ehb
 
@@ -464,6 +456,7 @@ __kvm_mips_return_to_guest:
        /* Disable RDHWR access */
        mtc0    zero, CP0_HWRENA
 
+       .set    noat
        /* load the guest context from VCPU and return */
        LONG_L  $0, VCPU_R0(k1)
        LONG_L  $1, VCPU_R1(k1)
@@ -509,6 +502,7 @@ FEXPORT(__kvm_mips_skip_guest_restore)
        LONG_L  k1, VCPU_R27(k1)
 
        eret
+       .set    at
 
 __kvm_mips_return_to_host:
        /* EBASE is already pointing to Linux */