arm64: KVM: Add ARCH_WORKAROUND_2 support for guests

commit 55e3748e8902ff641e334226bdcb432f9a5d78d3 upstream.

In order to offer ARCH_WORKAROUND_2 support to guests, we need
a bit of infrastructure.

Let's add a flag indicating whether or not the guest uses
SSBD mitigation. Depending on the state of this flag, allow
KVM to disable ARCH_WORKAROUND_2 before entering the guest,
and enable it when exiting it.

Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 4d6b17e23d316096b7c19db3d0694406037a137c..8a098e65f5f857bb35b64b70677dd0261ba9beeb 100644 (file)
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -254,6 +254,11 @@ static inline int kvm_map_vectors(void)
        return 0;
 }
 
+static inline int hyp_map_aux_data(void)
+{
+       return 0;
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ARM_KVM_MMU_H__ */

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index b956418f73bdce8aad22a1a5306dd1e05cdc2e4b..1a6d02350fc68955924ff6c3a728403acf50447b 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -33,6 +33,9 @@
 #define KVM_ARM64_DEBUG_DIRTY_SHIFT    0
 #define KVM_ARM64_DEBUG_DIRTY          (1 << KVM_ARM64_DEBUG_DIRTY_SHIFT)
 
+#define        VCPU_WORKAROUND_2_FLAG_SHIFT    0
+#define        VCPU_WORKAROUND_2_FLAG          (_AC(1, UL) << VCPU_WORKAROUND_2_FLAG_SHIFT)
+
 /* Translate a kernel address of @sym into its equivalent linear mapping */
 #define kvm_ksym_ref(sym)                                              \
        ({                                                              \

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 147389bd87b9c60e3eeae41836cea8c64387fc78..3d1774bcf108efda19d7a7f0c254e11c12e3f847 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -210,6 +210,9 @@ struct kvm_vcpu_arch {
        /* Exception Information */
        struct kvm_vcpu_fault_info fault;
 
+       /* State of various workarounds, see kvm_asm.h for bit assignment */
+       u64 workaround_flags;
+
        /* Guest debug state */
        u64 debug_flags;
 

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index c84e95e0e522403336c1504a0e4768a461c497c9..e42c1f0ae6cf7febfccba956ec0eed8ab47f4717 100644 (file)
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -383,5 +383,29 @@ static inline int kvm_map_vectors(void)
 }
 #endif
 
+#ifdef CONFIG_ARM64_SSBD
+DECLARE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+
+static inline int hyp_map_aux_data(void)
+{
+       int cpu, err;
+
+       for_each_possible_cpu(cpu) {
+               u64 *ptr;
+
+               ptr = per_cpu_ptr(&arm64_ssbd_callback_required, cpu);
+               err = create_hyp_mappings(ptr, ptr + 1, PAGE_HYP);
+               if (err)
+                       return err;
+       }
+       return 0;
+}
+#else
+static inline int hyp_map_aux_data(void)
+{
+       return 0;
+}
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* __ARM64_KVM_MMU_H__ */

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 1f41b0fe59bc85e7a80da604fdde336643ece023..b2f1992c6234cbbff1c1fbf6629160292bae4cc9 100644 (file)
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -15,6 +15,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/arm-smccc.h>
 #include <linux/types.h>
 #include <linux/jump_label.h>
 #include <uapi/linux/psci.h>
@@ -281,6 +282,39 @@ static void __hyp_text __skip_instr(struct kvm_vcpu *vcpu)
        write_sysreg_el2(*vcpu_pc(vcpu), elr);
 }
 
+static inline bool __hyp_text __needs_ssbd_off(struct kvm_vcpu *vcpu)
+{
+       if (!cpus_have_const_cap(ARM64_SSBD))
+               return false;
+
+       return !(vcpu->arch.workaround_flags & VCPU_WORKAROUND_2_FLAG);
+}
+
+static void __hyp_text __set_guest_arch_workaround_state(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_ARM64_SSBD
+       /*
+        * The host runs with the workaround always present. If the
+        * guest wants it disabled, so be it...
+        */
+       if (__needs_ssbd_off(vcpu) &&
+           __hyp_this_cpu_read(arm64_ssbd_callback_required))
+               arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2, 0, NULL);
+#endif
+}
+
+static void __hyp_text __set_host_arch_workaround_state(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_ARM64_SSBD
+       /*
+        * If the guest has disabled the workaround, bring it back on.
+        */
+       if (__needs_ssbd_off(vcpu) &&
+           __hyp_this_cpu_read(arm64_ssbd_callback_required))
+               arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2, 1, NULL);
+#endif
+}
+
 int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 {
        struct kvm_cpu_context *host_ctxt;
@@ -311,6 +345,8 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
        __sysreg_restore_guest_state(guest_ctxt);
        __debug_restore_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
 
+       __set_guest_arch_workaround_state(vcpu);
+
        /* Jump in the fire! */
 again:
        exit_code = __guest_enter(vcpu, host_ctxt);
@@ -367,6 +403,8 @@ again:
                /* 0 falls through to be handled out of EL2 */
        }
 
+       __set_host_arch_workaround_state(vcpu);
+
        if (cpus_have_const_cap(ARM64_HARDEN_BP_POST_GUEST_EXIT)) {
                u32 midr = read_cpuid_id();
 

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 4aede98b92eb5818f537333b28183476e509deee..d5f1d83645716e37d70136a29644f54ecb353512 100644 (file)
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1411,6 +1411,10 @@ static int init_hyp_mode(void)
                }
        }
 
+       err = hyp_map_aux_data();
+       if (err)
+               kvm_err("Cannot map host auxilary data: %d\n", err);
+
        return 0;
 
 out_err: