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    Subject[PATCH 4.17 096/101] arm64: KVM: Add ARCH_WORKAROUND_2 support for guests
    Date
    4.17-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Marc Zyngier <marc.zyngier@arm.com>

    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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm/include/asm/kvm_mmu.h | 5 ++++
    arch/arm64/include/asm/kvm_asm.h | 3 ++
    arch/arm64/include/asm/kvm_host.h | 3 ++
    arch/arm64/include/asm/kvm_mmu.h | 24 +++++++++++++++++++++
    arch/arm64/kvm/hyp/switch.c | 42 ++++++++++++++++++++++++++++++++++++++
    virt/kvm/arm/arm.c | 4 +++
    6 files changed, 81 insertions(+)

    --- a/arch/arm/include/asm/kvm_mmu.h
    +++ b/arch/arm/include/asm/kvm_mmu.h
    @@ -335,6 +335,11 @@ static inline int kvm_map_vectors(void)
    return 0;
    }

    +static inline int hyp_map_aux_data(void)
    +{
    + return 0;
    +}
    +
    #define kvm_phys_to_vttbr(addr) (addr)

    #endif /* !__ASSEMBLY__ */
    --- 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) \
    ({ \
    --- a/arch/arm64/include/asm/kvm_host.h
    +++ b/arch/arm64/include/asm/kvm_host.h
    @@ -216,6 +216,9 @@ 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;

    --- a/arch/arm64/include/asm/kvm_mmu.h
    +++ b/arch/arm64/include/asm/kvm_mmu.h
    @@ -473,6 +473,30 @@ 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
    +
    #define kvm_phys_to_vttbr(addr) phys_to_ttbr(addr)

    #endif /* __ASSEMBLY__ */
    --- 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>
    @@ -389,6 +390,39 @@ static bool __hyp_text fixup_guest_exit(
    return false;
    }

    +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
    +}
    +
    /* Switch to the guest for VHE systems running in EL2 */
    int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
    {
    @@ -409,6 +443,8 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vc
    sysreg_restore_guest_state_vhe(guest_ctxt);
    __debug_switch_to_guest(vcpu);

    + __set_guest_arch_workaround_state(vcpu);
    +
    do {
    /* Jump in the fire! */
    exit_code = __guest_enter(vcpu, host_ctxt);
    @@ -416,6 +452,8 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vc
    /* And we're baaack! */
    } while (fixup_guest_exit(vcpu, &exit_code));

    + __set_host_arch_workaround_state(vcpu);
    +
    fp_enabled = fpsimd_enabled_vhe();

    sysreg_save_guest_state_vhe(guest_ctxt);
    @@ -465,6 +503,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struc
    __sysreg_restore_state_nvhe(guest_ctxt);
    __debug_switch_to_guest(vcpu);

    + __set_guest_arch_workaround_state(vcpu);
    +
    do {
    /* Jump in the fire! */
    exit_code = __guest_enter(vcpu, host_ctxt);
    @@ -472,6 +512,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struc
    /* And we're baaack! */
    } while (fixup_guest_exit(vcpu, &exit_code));

    + __set_host_arch_workaround_state(vcpu);
    +
    fp_enabled = __fpsimd_enabled_nvhe();

    __sysreg_save_state_nvhe(guest_ctxt);
    --- a/virt/kvm/arm/arm.c
    +++ b/virt/kvm/arm/arm.c
    @@ -1490,6 +1490,10 @@ 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:

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