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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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