Hi Christoffer,
On 12.01.2018 13:07, Christoffer Dall wrote:
There is no need to enable/disable traps to FP registers on every switch
to/from the VM, because the host kernel does not use this resource
without calling vcpu_put. We can therefore move things around enough
that we still always write FPEXC32_EL2 before programming CPTR_EL2 but
only program these during vcpu load/put.
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_hyp.h | 6 +++++
arch/arm64/kvm/hyp/switch.c | 51 +++++++++++++++++++++++++++++-----------
arch/arm64/kvm/hyp/sysreg-sr.c | 12 ++++++++--
3 files changed, 53 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 3f54c55f77a1..ffd62e31f134 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -148,6 +148,12 @@ void __fpsimd_save_state(struct user_fpsimd_state *fp_regs);
void __fpsimd_restore_state(struct user_fpsimd_state *fp_regs);
bool __fpsimd_enabled(void);
+void __activate_traps_nvhe_load(struct kvm_vcpu *vcpu);
+void __deactivate_traps_nvhe_put(void);
+
+void activate_traps_vhe_load(struct kvm_vcpu *vcpu);
+void deactivate_traps_vhe_put(void);
+
u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
void __noreturn __hyp_do_panic(unsigned long, ...);
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index c01bcfc3fb52..d14ab9650f81 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -24,22 +24,25 @@
#include <asm/fpsimd.h>
#include <asm/debug-monitors.h>
-static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
+static void __hyp_text __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
{
/*
- * We are about to set CPTR_EL2.TFP to trap all floating point
- * register accesses to EL2, however, the ARM ARM clearly states that
- * traps are only taken to EL2 if the operation would not otherwise
- * trap to EL1. Therefore, always make sure that for 32-bit guests,
- * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
- * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
- * it will cause an exception.
+ * We are about to trap all floating point register accesses to EL2,
+ * however, traps are only taken to EL2 if the operation would not
+ * otherwise trap to EL1. Therefore, always make sure that for 32-bit
+ * guests, we set FPEXC.EN to prevent traps to EL1, when setting the
+ * TFP bit. If FP/ASIMD is not implemented, FPEXC is UNDEFINED and
+ * any access to it will cause an exception.
*/
if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd() &&
!vcpu->arch.guest_vfp_loaded) {
write_sysreg(1 << 30, fpexc32_el2);
isb();
}
+}
+
+static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
+{
write_sysreg(vcpu->arch.hcr_el2, hcr_el2);
/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
@@ -61,10 +64,12 @@ static void __hyp_text __deactivate_traps_common(void)
write_sysreg(0, pmuserenr_el0);
}
-static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
+void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
{
u64 val;
+ __activate_traps_fpsimd32(vcpu);
+
val = read_sysreg(cpacr_el1);
val |= CPACR_EL1_TTA;
val &= ~CPACR_EL1_ZEN;
@@ -73,14 +78,26 @@ static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
else
val &= ~CPACR_EL1_FPEN;
write_sysreg(val, cpacr_el1);
Giving that you move this code to kvm_vcpu_load_sysregs() I am wondering
if we have to deactivate FPEN trap here. IIUC, we call
kvm_vcpu_load_sysregs()->activate_traps_vhe_load() and then
kvm_vcpu_put_sysregs() by design. So vcpu->arch.guest_vfp_loaded should
be always 0 here since it is zeroed in kvm_vcpu_put_sysregs(). The same
for nvhe case below.
I might miss some scenario or future changes you are planning to do. Let
me know your thoughts.
Thanks,
Tomasz
+}
+void deactivate_traps_vhe_put(void)
+{
+ write_sysreg(CPACR_EL1_DEFAULT, cpacr_el1);
+}
+
+static void __hyp_text __activate_traps_vhe(struct kvm_vcpu *vcpu)
+{
write_sysreg(__kvm_hyp_vector, vbar_el1);
}
-static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
+void __hyp_text __activate_traps_nvhe_load(struct kvm_vcpu *vcpu)
{
u64 val;
+ vcpu = kern_hyp_va(vcpu);
+
+ __activate_traps_fpsimd32(vcpu);
+
val = CPTR_EL2_DEFAULT;
val |= CPTR_EL2_TTA | CPTR_EL2_TZ;
if (vcpu->arch.guest_vfp_loaded)
@@ -90,6 +107,15 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
write_sysreg(val, cptr_el2);
}
+void __hyp_text __deactivate_traps_nvhe_put(void)
+{
+ write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
+}
+
+static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
+{
+}
+
static hyp_alternate_select(__activate_traps_arch,
__activate_traps_nvhe, __activate_traps_vhe,
ARM64_HAS_VIRT_HOST_EXTN);
@@ -111,12 +137,10 @@ static void __hyp_text __deactivate_traps_vhe(void)
write_sysreg(mdcr_el2, mdcr_el2);
write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2);
- write_sysreg(CPACR_EL1_DEFAULT, cpacr_el1);
write_sysreg(vectors, vbar_el1);
}
-static void __hyp_text __deactivate_traps_nvhe(void)
-{
+static void __hyp_text __deactivate_traps_nvhe(void) {
u64 mdcr_el2 = read_sysreg(mdcr_el2);
mdcr_el2 &= MDCR_EL2_HPMN_MASK;
@@ -124,7 +148,6 @@ static void __hyp_text __deactivate_traps_nvhe(void)
write_sysreg(mdcr_el2, mdcr_el2);
write_sysreg(HCR_RW, hcr_el2);
- write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
}
static hyp_alternate_select(__deactivate_traps_arch,
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index d225f5797651..7943d5b4dbcb 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -237,8 +237,10 @@ void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *host_ctxt = vcpu->arch.host_cpu_context;
struct kvm_cpu_context *guest_ctxt = &vcpu->arch.ctxt;
- if (!has_vhe())
+ if (!has_vhe()) {
+ kvm_call_hyp(__activate_traps_nvhe_load, vcpu);
return;
+ }
__sysreg_save_user_state(host_ctxt);
@@ -253,6 +255,8 @@ void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu)
__sysreg_restore_el1_state(guest_ctxt);
vcpu->arch.sysregs_loaded_on_cpu = true;
+
+ activate_traps_vhe_load(vcpu);
}
/**
@@ -282,8 +286,12 @@ void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu)
vcpu->arch.guest_vfp_loaded = 0;
}
- if (!has_vhe())
+ if (!has_vhe()) {
+ kvm_call_hyp(__deactivate_traps_nvhe_put);
return;
+ }
+
+ deactivate_traps_vhe_put();
__sysreg_save_el1_state(guest_ctxt);
__sysreg_save_user_state(guest_ctxt);
