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    Subject[PATCH 4.14 70/92] KVM: arm64: Store vcpu on the stack during __guest_enter()
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: James Morse <james.morse@arm.com>

    Commit 32b03d1059667a39e089c45ee38ec9c16332430f upstream.

    KVM uses tpidr_el2 as its private vcpu register, which makes sense for
    non-vhe world switch as only KVM can access this register. This means
    vhe Linux has to use tpidr_el1, which KVM has to save/restore as part
    of the host context.

    If the SDEI handler code runs behind KVMs back, it mustn't access any
    per-cpu variables. To allow this on systems with vhe we need to make
    the host use tpidr_el2, saving KVM from save/restoring it.

    __guest_enter() stores the host_ctxt on the stack, do the same with
    the vcpu.

    Signed-off-by: James Morse <james.morse@arm.com>
    Reviewed-by: Christoffer Dall <cdall@linaro.org>
    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>
    ---
    arch/arm64/kvm/hyp/entry.S | 10 +++++++---
    arch/arm64/kvm/hyp/hyp-entry.S | 6 +++---
    2 files changed, 10 insertions(+), 6 deletions(-)

    --- a/arch/arm64/kvm/hyp/entry.S
    +++ b/arch/arm64/kvm/hyp/entry.S
    @@ -62,8 +62,8 @@ ENTRY(__guest_enter)
    // Store the host regs
    save_callee_saved_regs x1

    - // Store the host_ctxt for use at exit time
    - str x1, [sp, #-16]!
    + // Store host_ctxt and vcpu for use at exit time
    + stp x1, x0, [sp, #-16]!

    add x18, x0, #VCPU_CONTEXT

    @@ -159,6 +159,10 @@ abort_guest_exit_end:
    ENDPROC(__guest_exit)

    ENTRY(__fpsimd_guest_restore)
    + // x0: esr
    + // x1: vcpu
    + // x2-x29,lr: vcpu regs
    + // vcpu x0-x1 on the stack
    stp x2, x3, [sp, #-16]!
    stp x4, lr, [sp, #-16]!

    @@ -173,7 +177,7 @@ alternative_else
    alternative_endif
    isb

    - mrs x3, tpidr_el2
    + mov x3, x1

    ldr x0, [x3, #VCPU_HOST_CONTEXT]
    kern_hyp_va x0
    --- a/arch/arm64/kvm/hyp/hyp-entry.S
    +++ b/arch/arm64/kvm/hyp/hyp-entry.S
    @@ -120,6 +120,7 @@ el1_trap:
    /*
    * x0: ESR_EC
    */
    + ldr x1, [sp, #16 + 8] // vcpu stored by __guest_enter

    /*
    * We trap the first access to the FP/SIMD to save the host context
    @@ -132,19 +133,18 @@ alternative_if_not ARM64_HAS_NO_FPSIMD
    b.eq __fpsimd_guest_restore
    alternative_else_nop_endif

    - mrs x1, tpidr_el2
    mov x0, #ARM_EXCEPTION_TRAP
    b __guest_exit

    el1_irq:
    stp x0, x1, [sp, #-16]!
    - mrs x1, tpidr_el2
    + ldr x1, [sp, #16 + 8]
    mov x0, #ARM_EXCEPTION_IRQ
    b __guest_exit

    el1_error:
    stp x0, x1, [sp, #-16]!
    - mrs x1, tpidr_el2
    + ldr x1, [sp, #16 + 8]
    mov x0, #ARM_EXCEPTION_EL1_SERROR
    b __guest_exit


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