KVM: arm64: Store vcpu on the stack during __guest_enter()

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>

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 12ee62d6d410803e2aa7a10dd0df9acb41cf3076..9a8ab5dddd9e54450a6dae4df5bb988645bf2e56 100644 (file)
--- 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

diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 4e9d50c3e658b46ae2b0b6f4aacd717ed895b5b5..acd75c905084830f004c5662e9e92f3a46f97a20 100644 (file)
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -121,24 +121,24 @@ el1_trap:
        /*
         * x0: ESR_EC
         */
+       ldr     x1, [sp, #16 + 8]       // vcpu stored by __guest_enter
 
        /* Guest accessed VFP/SIMD registers, save host, restore Guest */
        cmp     x0, #ESR_ELx_EC_FP_ASIMD
        b.eq    __fpsimd_guest_restore
 
-       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