[PATCH v3 23/66] KVM: arm64: nv: Respect virtual CPTR_EL2.{TFP,FPEN} settings

Marc Zyngier
2020-12-10T16:29:22Z

From: Jintack Lim <jintack.lim@linaro.org>

Forward traps due to FP/ASIMD register accesses to the virtual EL2
if virtual CPTR_EL2.TFP is set (with HCR_EL2.E2H == 0) or
CPTR_EL2.FPEN is configure to do so (with HCR_EL2.E2h == 1).

Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
[maz: account for HCR_EL2.E2H when testing for TFP/FPEN, with
all the hard work actually being done by Chase Conklin]
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_emulate.h | 26 +++++++++++++++++++++++++
arch/arm64/kvm/handle_exit.c | 16 +++++++++++----
arch/arm64/kvm/hyp/include/hyp/switch.h | 11 +++++++++--
3 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5c7dc659e8c4..a000e6e05091 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -11,12 +11,14 @@
#ifndef __ARM64_KVM_EMULATE_H__
#define __ARM64_KVM_EMULATE_H__

+#include <linux/bitfield.h>
#include <linux/kvm_host.h>

#include <asm/debug-monitors.h>
#include <asm/esr.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_hyp.h>
+#include <asm/kvm_nested.h>
#include <asm/ptrace.h>
#include <asm/cputype.h>
#include <asm/virt.h>
@@ -321,6 +323,30 @@ static inline bool vcpu_mode_priv(const struct kvm_vcpu *vcpu)
return mode != PSR_MODE_EL0t;
}

+static inline bool guest_hyp_fpsimd_traps_enabled(const struct kvm_vcpu *vcpu)
+{
+ u64 val;
+
+ if (!nested_virt_in_use(vcpu))
+ return false;
+
+ val = vcpu_read_sys_reg(vcpu, CPTR_EL2);
+
+ if (!vcpu_el2_e2h_is_set(vcpu))
+ return (val & CPTR_EL2_TFP);
+
+ switch (FIELD_GET(CPACR_EL1_FPEN, val)) {
+ case 0b00:
+ case 0b10:
+ return true;
+ case 0b01:
+ return vcpu_el2_tge_is_set(vcpu) && !vcpu_mode_el2(vcpu);
+ case 0b11:
+ default: /* GCC is dumb */
+ return false;
+ }
+}
+
static __always_inline u32 kvm_vcpu_get_esr(const struct kvm_vcpu *vcpu)
{
return vcpu->arch.fault.esr_el2;
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index a2437b2380f1..5276e8563367 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -96,11 +96,19 @@ static int handle_smc(struct kvm_vcpu *vcpu)
}

/*
- * Guest access to FP/ASIMD registers are routed to this handler only
- * when the system doesn't support FP/ASIMD.
+ * This handles the cases where the system does not support FP/ASIMD or when
+ * we are running nested virtualization and the guest hypervisor is trapping
+ * FP/ASIMD accesses by its guest guest.
+ *
+ * All other handling of guest vs. host FP/ASIMD register state is handled in
+ * fixup_guest_exit().
*/
-static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
+static int kvm_handle_fpasimd(struct kvm_vcpu *vcpu)
{
+ if (guest_hyp_fpsimd_traps_enabled(vcpu))
+ return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
+ /* This is the case when the system doesn't support FP/ASIMD. */
kvm_inject_undefined(vcpu);
return 1;
}
@@ -243,7 +251,7 @@ static exit_handle_fn arm_exit_handlers[] = {
[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,
[ESR_ELx_EC_PAC] = kvm_handle_ptrauth,
};

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 424b074e4377..e5e201314c87 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -223,11 +223,18 @@ static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
esr_ec != ESR_ELx_EC_SVE)
return false;

- /* Don't handle SVE traps for non-SVE vcpus here: */
- if (!sve_guest)
+ /*
+ * Don't handle SVE traps for non-SVE vcpus here. This
+ * includes NV guests for the time being.
+ */
+ if (!sve_guest) {
if (esr_ec != ESR_ELx_EC_FP_ASIMD)
return false;

+ if (guest_hyp_fpsimd_traps_enabled(vcpu))
+ return false;
+ }
+
/* Valid trap. Switch the context: */

if (vhe) {
--
2.29.2