[PATCH v4 28/40] KVM: arm64: Defer saving/restoring 64-bit sysregs to vcpu load/put on VHE
Christoffer Dall
christoffer.dall at linaro.org
Thu Feb 15 13:03:20 PST 2018
Some system registers do not affect the host kernel's execution and can
therefore be loaded when we are about to run a VCPU and we don't have to
restore the host state to the hardware before the time when we are
actually about to return to userspace or schedule out the VCPU thread.
The EL1 system registers and the userspace state registers only
affecting EL0 execution do not need to be saved and restored on every
switch between the VM and the host, because they don't affect the host
kernel's execution.
We mark all registers which are now deffered as such in the
vcpu_{read,write}_sys_reg accessors in sys-regs.c to ensure the most
up-to-date copy is always accessed.
Note MPIDR_EL1 (controlled via VMPIDR_EL2) is accessed from other vcpu
threads, for example via the GIC emulation, and therefore must be
declared as immediate, which is fine as the guest cannot modify this
value.
The 32-bit sysregs can also be deferred but we do this in a separate
patch as it requires a bit more infrastructure.
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---
Notes:
Changes since v3:
- Changed to switch-based sysreg approach
arch/arm64/kvm/hyp/sysreg-sr.c | 39 +++++++++++++++++++++++++++++++--------
arch/arm64/kvm/sys_regs.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 71 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 906606dc4e2c..9c60b8062724 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -25,8 +25,12 @@
/*
* Non-VHE: Both host and guest must save everything.
*
- * VHE: Host must save tpidr*_el0, mdscr_el1, sp_el0,
- * and guest must save everything.
+ * VHE: Host and guest must save mdscr_el1 and sp_el0 (and the PC and pstate,
+ * which are handled as part of the el2 return state) on every switch.
+ * tpidr_el0 and tpidrro_el0 only need to be switched when going
+ * to host userspace or a different VCPU. EL1 registers only need to be
+ * switched when potentially going to run a different VCPU. The latter two
+ * classes are handled as part of kvm_arch_vcpu_load and kvm_arch_vcpu_put.
*/
static void __hyp_text __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
@@ -93,14 +97,11 @@ void __hyp_text __sysreg_save_state_nvhe(struct kvm_cpu_context *ctxt)
void sysreg_save_host_state_vhe(struct kvm_cpu_context *ctxt)
{
__sysreg_save_common_state(ctxt);
- __sysreg_save_user_state(ctxt);
}
void sysreg_save_guest_state_vhe(struct kvm_cpu_context *ctxt)
{
- __sysreg_save_el1_state(ctxt);
__sysreg_save_common_state(ctxt);
- __sysreg_save_user_state(ctxt);
__sysreg_save_el2_return_state(ctxt);
}
@@ -169,14 +170,11 @@ void __hyp_text __sysreg_restore_state_nvhe(struct kvm_cpu_context *ctxt)
void sysreg_restore_host_state_vhe(struct kvm_cpu_context *ctxt)
{
__sysreg_restore_common_state(ctxt);
- __sysreg_restore_user_state(ctxt);
}
void sysreg_restore_guest_state_vhe(struct kvm_cpu_context *ctxt)
{
- __sysreg_restore_el1_state(ctxt);
__sysreg_restore_common_state(ctxt);
- __sysreg_restore_user_state(ctxt);
__sysreg_restore_el2_return_state(ctxt);
}
@@ -240,6 +238,18 @@ void __hyp_text __sysreg32_restore_state(struct kvm_vcpu *vcpu)
*/
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())
+ return;
+
+ __sysreg_save_user_state(host_ctxt);
+
+ __sysreg_restore_user_state(guest_ctxt);
+ __sysreg_restore_el1_state(guest_ctxt);
+
+ vcpu->arch.sysregs_loaded_on_cpu = true;
}
/**
@@ -255,6 +265,19 @@ void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu)
*/
void kvm_vcpu_put_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())
+ return;
+
+ __sysreg_save_el1_state(guest_ctxt);
+ __sysreg_save_user_state(guest_ctxt);
+
+ /* Restore host user state */
+ __sysreg_restore_user_state(host_ctxt);
+
+ vcpu->arch.sysregs_loaded_on_cpu = false;
}
void __hyp_text __kvm_set_tpidr_el2(u64 tpidr_el2)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index b3c3f014aa61..f060309337aa 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -87,6 +87,26 @@ u64 vcpu_read_sys_reg(struct kvm_vcpu *vcpu, int reg)
* exit from the guest but are only saved on vcpu_put.
*/
switch (reg) {
+ case CSSELR_EL1: return read_sysreg_s(SYS_CSSELR_EL1);
+ case SCTLR_EL1: return read_sysreg_s(sctlr_EL12);
+ case ACTLR_EL1: return read_sysreg_s(SYS_ACTLR_EL1);
+ case CPACR_EL1: return read_sysreg_s(cpacr_EL12);
+ case TTBR0_EL1: return read_sysreg_s(ttbr0_EL12);
+ case TTBR1_EL1: return read_sysreg_s(ttbr1_EL12);
+ case TCR_EL1: return read_sysreg_s(tcr_EL12);
+ case ESR_EL1: return read_sysreg_s(esr_EL12);
+ case AFSR0_EL1: return read_sysreg_s(afsr0_EL12);
+ case AFSR1_EL1: return read_sysreg_s(afsr1_EL12);
+ case FAR_EL1: return read_sysreg_s(far_EL12);
+ case MAIR_EL1: return read_sysreg_s(mair_EL12);
+ case VBAR_EL1: return read_sysreg_s(vbar_EL12);
+ case CONTEXTIDR_EL1: return read_sysreg_s(contextidr_EL12);
+ case TPIDR_EL0: return read_sysreg_s(SYS_TPIDR_EL0);
+ case TPIDRRO_EL0: return read_sysreg_s(SYS_TPIDRRO_EL0);
+ case TPIDR_EL1: return read_sysreg_s(SYS_TPIDR_EL1);
+ case AMAIR_EL1: return read_sysreg_s(amair_EL12);
+ case CNTKCTL_EL1: return read_sysreg_s(cntkctl_EL12);
+ case PAR_EL1: return read_sysreg_s(SYS_PAR_EL1);
}
immediate_read:
@@ -103,6 +123,26 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, int reg, u64 val)
* entry to the guest but are only restored on vcpu_load.
*/
switch (reg) {
+ case CSSELR_EL1: write_sysreg_s(val, SYS_CSSELR_EL1); return;
+ case SCTLR_EL1: write_sysreg_s(val, sctlr_EL12); return;
+ case ACTLR_EL1: write_sysreg_s(val, SYS_ACTLR_EL1); return;
+ case CPACR_EL1: write_sysreg_s(val, cpacr_EL12); return;
+ case TTBR0_EL1: write_sysreg_s(val, ttbr0_EL12); return;
+ case TTBR1_EL1: write_sysreg_s(val, ttbr1_EL12); return;
+ case TCR_EL1: write_sysreg_s(val, tcr_EL12); return;
+ case ESR_EL1: write_sysreg_s(val, esr_EL12); return;
+ case AFSR0_EL1: write_sysreg_s(val, afsr0_EL12); return;
+ case AFSR1_EL1: write_sysreg_s(val, afsr1_EL12); return;
+ case FAR_EL1: write_sysreg_s(val, far_EL12); return;
+ case MAIR_EL1: write_sysreg_s(val, mair_EL12); return;
+ case VBAR_EL1: write_sysreg_s(val, vbar_EL12); return;
+ case CONTEXTIDR_EL1: write_sysreg_s(val, contextidr_EL12); return;
+ case TPIDR_EL0: write_sysreg_s(val, SYS_TPIDR_EL0); return;
+ case TPIDRRO_EL0: write_sysreg_s(val, SYS_TPIDRRO_EL0); return;
+ case TPIDR_EL1: write_sysreg_s(val, SYS_TPIDR_EL1); return;
+ case AMAIR_EL1: write_sysreg_s(val, amair_EL12); return;
+ case CNTKCTL_EL1: write_sysreg_s(val, cntkctl_EL12); return;
+ case PAR_EL1: write_sysreg_s(val, SYS_PAR_EL1); return;
}
immediate_write:
--
2.14.2
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