The conversion of the FPSIMD context switch trap code to C has added
some overhead to calling it, due to the need to save registers that
the procedure call standard defines as caller-saved.
So, perhaps it is no longer worth invoking this trap handler quite
so early.
Instead, we can invoke it from fixup_guest_exit(), with little
likelihood of increasing the overhead much further.
As a convenience, this patch gives __hyp_switch_fpsimd() the same
return semantics fixup_guest_exit(). For now there is no
possibility of a spurious FPSIMD trap, so the function always
returns true, but this allows it to be tail-called with a single
return statement.
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxx>
---
arch/arm64/kvm/hyp/entry.S | 30 ------------------------------
arch/arm64/kvm/hyp/hyp-entry.S | 19 -------------------
arch/arm64/kvm/hyp/switch.c | 15 +++++++++++++--
3 files changed, 13 insertions(+), 51 deletions(-)
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 40f349b..fad1e16 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -166,33 +166,3 @@ abort_guest_exit_end:
orr x0, x0, x5
1: ret
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, #-144]!
- stp x4, x5, [sp, #16]
- stp x6, x7, [sp, #32]
- stp x8, x9, [sp, #48]
- stp x10, x11, [sp, #64]
- stp x12, x13, [sp, #80]
- stp x14, x15, [sp, #96]
- stp x16, x17, [sp, #112]
- stp x18, lr, [sp, #128]
-
- bl __hyp_switch_fpsimd
-
- ldp x4, x5, [sp, #16]
- ldp x6, x7, [sp, #32]
- ldp x8, x9, [sp, #48]
- ldp x10, x11, [sp, #64]
- ldp x12, x13, [sp, #80]
- ldp x14, x15, [sp, #96]
- ldp x16, x17, [sp, #112]
- ldp x18, lr, [sp, #128]
- ldp x0, x1, [sp, #144]
- ldp x2, x3, [sp], #160
- eret
-ENDPROC(__fpsimd_guest_restore)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index bffece2..753b9d2 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -113,25 +113,6 @@ el1_hvc_guest:
el1_trap:
get_vcpu_ptr x1, x0
-
- mrs x0, esr_el2
- lsr x0, x0, #ESR_ELx_EC_SHIFT
- /*
- * x0: ESR_EC
- * x1: vcpu pointer
- */
-
- /*
- * We trap the first access to the FP/SIMD to save the host context
- * and restore the guest context lazily.
- * If FP/SIMD is not implemented, handle the trap and inject an
- * undefined instruction exception to the guest.
- */
-alternative_if_not ARM64_HAS_NO_FPSIMD
- cmp x0, #ESR_ELx_EC_FP_ASIMD
- b.eq __fpsimd_guest_restore
-alternative_else_nop_endif
-
mov x0, #ARM_EXCEPTION_TRAP
b __guest_exit
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 4fbee95..2d45bd7 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -328,8 +328,7 @@ static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu)
}
}
-void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
- struct kvm_vcpu *vcpu)
+static bool __hyp_text __hyp_switch_fpsimd(struct kvm_vcpu *vcpu)
{
struct user_fpsimd_state *host_fpsimd = vcpu->arch.host_fpsimd_state;
@@ -369,6 +368,8 @@ void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
fpexc32_el2);
vcpu->arch.flags |= KVM_ARM64_FP_ENABLED;
+
+ return true;
}
/*
@@ -390,6 +391,16 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
if (*exit_code != ARM_EXCEPTION_TRAP)
goto exit;
+ /*
+ * We trap the first access to the FP/SIMD to save the host context
+ * and restore the guest context lazily.
+ * If FP/SIMD is not implemented, handle the trap and inject an
+ * undefined instruction exception to the guest.
+ */
+ if (system_supports_fpsimd() &&
+ kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_FP_ASIMD)
+ return __hyp_switch_fpsimd(vcpu);
+
if (!__populate_fault_info(vcpu))
return true;
--
2.1.4
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