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Subject[RFC PATCH v2 25/38] KVM: arm64: Respect virtual CPTR_EL2.TFP setting
Date
Forward traps due to FP/ASIMD register accesses to the virtual EL2 if
virtual CPTR_EL2.TFP is set. Note that if TFP bit is set, then even
accesses to FP/ASIMD register from EL2 as well as NS EL0/1 will trap to
EL2. So, we don't check the VM's exception level.

Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
---
arch/arm64/kernel/asm-offsets.c | 1 +
arch/arm64/kvm/handle_exit.c | 15 +++++++++++----
arch/arm64/kvm/hyp/entry.S | 13 +++++++++++++
arch/arm64/kvm/hyp/hyp-entry.S | 2 +-
4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index b3bb7ef..f5117a3 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -134,6 +134,7 @@ int main(void)
DEFINE(CPU_FP_REGS, offsetof(struct kvm_regs, fp_regs));
DEFINE(VCPU_FPEXC32_EL2, offsetof(struct kvm_vcpu, arch.ctxt.sys_regs[FPEXC32_EL2]));
DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_context));
+ DEFINE(VIRTUAL_CPTR_EL2, offsetof(struct kvm_vcpu, arch.ctxt.sys_regs[CPTR_EL2]));
#endif
#ifdef CONFIG_CPU_PM
DEFINE(CPU_SUSPEND_SZ, sizeof(struct cpu_suspend_ctx));
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 25ec824..d4e7b2b 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -84,11 +84,18 @@ static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
}

/*
- * Guest access to FP/ASIMD registers are routed to this handler only
- * when the system doesn't support FP/ASIMD.
+ * When the system supports FP/ASMID and we are NOT running nested
+ * virtualization, FP/ASMID traps are handled in EL2 directly.
+ * This handler handles the cases those are not belong to the above case.
*/
-static int handle_no_fpsimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
+static int kvm_handle_fpasimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
+
+ /* This is for nested virtualization */
+ if (vcpu_sys_reg(vcpu, CPTR_EL2) & CPTR_EL2_TFP)
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
+ /* This is the case when the system doesn't support FP/ASIMD. */
kvm_inject_undefined(vcpu);
return 1;
}
@@ -220,7 +227,7 @@ static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug,
[ESR_ELx_EC_BRK64] = kvm_handle_guest_debug,
- [ESR_ELx_EC_FP_ASIMD] = handle_no_fpsimd,
+ [ESR_ELx_EC_FP_ASIMD] = kvm_handle_fpasimd,
};

static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 12ee62d..95af673 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -158,6 +158,19 @@ abort_guest_exit_end:
1: ret
ENDPROC(__guest_exit)

+ENTRY(__fpsimd_guest_trap)
+ // If virtual CPTR_EL2.TFP is set, then forward the trap to the
+ // virtual EL2. For the non-nested case, this bit is always 0.
+ mrs x1, tpidr_el2
+ ldr x0, [x1, #VIRTUAL_CPTR_EL2]
+ and x0, x0, #CPTR_EL2_TFP
+ cbnz x0, 1f
+ b __fpsimd_guest_restore
+1:
+ mov x0, #ARM_EXCEPTION_TRAP
+ b __guest_exit
+ENDPROC(__fpsimd_guest_trap)
+
ENTRY(__fpsimd_guest_restore)
stp x2, x3, [sp, #-16]!
stp x4, lr, [sp, #-16]!
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 5170ce1..ab169fd 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -113,7 +113,7 @@ el1_trap:
*/
alternative_if_not ARM64_HAS_NO_FPSIMD
cmp x0, #ESR_ELx_EC_FP_ASIMD
- b.eq __fpsimd_guest_restore
+ b.eq __fpsimd_guest_trap
alternative_else_nop_endif

mrs x1, tpidr_el2
--
1.9.1
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