diff mbox series

[v8,16/69] KVM: arm64: nv: Handle HCR_EL2.E2H specially

Message ID 20230131092504.2880505-17-maz@kernel.org (mailing list archive)
State New, archived
Headers show
Series KVM: arm64: ARMv8.3/8.4 Nested Virtualization support | expand

Commit Message

Marc Zyngier Jan. 31, 2023, 9:24 a.m. UTC 
HCR_EL2.E2H is nasty, as a flip of this bit completely changes the way
we deal with a lot of the state. So when the guest flips this bit
(sysregs are live), do the put/load dance so that we have a consistent
state.

Yes, this is slow. Don't do it.

Suggested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
diff mbox series

Patch

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4975c5222f73..26d189f908a7 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -180,9 +180,24 @@  void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
 		goto memory_write;
 
 	if (unlikely(get_el2_to_el1_mapping(reg, &el1r, &xlate))) {
+		bool need_put_load;
+
 		if (!is_hyp_ctxt(vcpu))
 			goto memory_write;
 
+		/*
+		 * HCR_EL2.E2H is nasty: it changes the way we interpret a
+		 * lot of the EL2 state, so treat is as a full state
+		 * transition.
+		 */
+		need_put_load = ((reg == HCR_EL2) &&
+				 vcpu_el2_e2h_is_set(vcpu) != !!(val & HCR_E2H));
+
+		if (need_put_load) {
+			preempt_disable();
+			kvm_arch_vcpu_put(vcpu);
+		}
+
 		/*
 		 * Always store a copy of the write to memory to avoid having
 		 * to reverse-translate virtual EL2 system registers for a
@@ -190,6 +205,11 @@  void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
 		 */
 		__vcpu_sys_reg(vcpu, reg) = val;
 
+		if (need_put_load) {
+			kvm_arch_vcpu_load(vcpu, smp_processor_id());
+			preempt_enable();
+		}
+
 		switch (reg) {
 		case ELR_EL2:
 			write_sysreg_el1(val, SYS_ELR);