KVM: PPC: Book3S PR: Load up SPRG3 register with guest value on guest entry

Unlike the other general-purpose SPRs, SPRG3 can be read by usermode
code, and is used in recent kernels to store the CPU and NUMA node
numbers so that they can be read by VDSO functions.  Thus we need to
load the guest's SPRG3 value into the real SPRG3 register when entering
the guest, and restore the host's value when exiting the guest.  We don't
need to save the guest SPRG3 value when exiting the guest as usermode
code can't modify SPRG3.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 6f16ffafa6f01542d54ccc684c3f8d5d7d6add5c..a67c76ef5feb1a0109b7fdad83a71fe7d9c06341 100644 (file)
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -452,6 +452,7 @@ int main(void)
        DEFINE(VCPU_SPRG2, offsetof(struct kvm_vcpu, arch.shregs.sprg2));
        DEFINE(VCPU_SPRG3, offsetof(struct kvm_vcpu, arch.shregs.sprg3));
 #endif
+       DEFINE(VCPU_SHARED_SPRG3, offsetof(struct kvm_vcpu_arch_shared, sprg3));
        DEFINE(VCPU_SHARED_SPRG4, offsetof(struct kvm_vcpu_arch_shared, sprg4));
        DEFINE(VCPU_SHARED_SPRG5, offsetof(struct kvm_vcpu_arch_shared, sprg5));
        DEFINE(VCPU_SHARED_SPRG6, offsetof(struct kvm_vcpu_arch_shared, sprg6));

diff --git a/arch/powerpc/kvm/book3s_interrupts.S b/arch/powerpc/kvm/book3s_interrupts.S
index 48cbbf862958f8e3eea8b82932ec03cf231595b0..17cfae5497a3384d756fb2ed63b775758e6efb19 100644 (file)
--- a/arch/powerpc/kvm/book3s_interrupts.S
+++ b/arch/powerpc/kvm/book3s_interrupts.S
@@ -92,6 +92,11 @@ kvm_start_lightweight:
        PPC_LL  r3, VCPU_HFLAGS(r4)
        rldicl  r3, r3, 0, 63           /* r3 &= 1 */
        stb     r3, HSTATE_RESTORE_HID5(r13)
+
+       /* Load up guest SPRG3 value, since it's user readable */
+       ld      r3, VCPU_SHARED(r4)
+       ld      r3, VCPU_SHARED_SPRG3(r3)
+       mtspr   SPRN_SPRG3, r3
 #endif /* CONFIG_PPC_BOOK3S_64 */
 
        PPC_LL  r4, VCPU_SHADOW_MSR(r4) /* get shadow_msr */
@@ -123,6 +128,15 @@ kvmppc_handler_highmem:
        /* R7 = vcpu */
        PPC_LL  r7, GPR4(r1)
 
+#ifdef CONFIG_PPC_BOOK3S_64
+       /*
+        * Reload kernel SPRG3 value.
+        * No need to save guest value as usermode can't modify SPRG3.
+        */
+       ld      r3, PACA_SPRG3(r13)
+       mtspr   SPRN_SPRG3, r3
+#endif /* CONFIG_PPC_BOOK3S_64 */
+
        PPC_STL r14, VCPU_GPR(R14)(r7)
        PPC_STL r15, VCPU_GPR(R15)(r7)
        PPC_STL r16, VCPU_GPR(R16)(r7)