[RFC PATCH v1 10/17] target/riscv/kvm: skip unsupported KVM requests for a CoVE guest

[Baolong Duan <blduan@linux.alibaba.com>]

A TEE VM has no APLIC and no PLIC, and its timer state lives inside the
TVM where the host cannot read it.  Skip the KVM requests that would fail
or return meaningless data: reading the timer back, injecting a wired
interrupt, and the APLIC part of the in-kernel AIA setup.

Note that kvm_mark_guest_state_protected(), which SEV and TDX use, would
cover the vCPU state part of this generically.  It is not used here
because it also changes the reset and migration paths, which have not
been evaluated for CoVE yet.

Signed-off-by: Baolong Duan <blduan@linux.alibaba.com>
---
 target/riscv/kvm/kvm-cpu.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
index 67c99d68ce..23c2ae2214 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -1477,7 +1477,13 @@ static void kvm_riscv_vm_state_change(void *opaque, bool running,
     if (running) {
         kvm_riscv_put_regs_timer(cs);
     } else {
-        kvm_riscv_get_regs_timer(cs);
+        /*
+         * The timer state of a CoVE guest is kept inside the TVM and cannot
+         * be read back by the host.
+         */
+        if (!riscv_cove_vm_active()) {
+            kvm_riscv_get_regs_timer(cs);
+        }
     }
 }
 
@@ -1791,6 +1797,14 @@ void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level)
     int ret;
     unsigned virq = level ? KVM_INTERRUPT_SET : KVM_INTERRUPT_UNSET;
 
+    /*
+     * A CoVE guest has neither APLIC nor PLIC, so there is no wired
+     * interrupt to inject.
+     */
+    if (riscv_cove_vm_active()) {
+        return;
+    }
+
     if (irq != IRQ_S_EXT) {
         perror("kvm riscv set irq != IRQ_S_EXT\n");
         abort();
@@ -1924,8 +1938,11 @@ void kvm_riscv_aia_create(MachineState *machine, uint64_t group_shift,
      * This is done by leaving KVM_DEV_RISCV_AIA_CONFIG_SRCS
      * unset. We can also skip KVM_DEV_RISCV_AIA_ADDR_APLIC
      * since KVM won't be using it.
+     *
+     * The same applies to a CoVE guest: KVM does not implement an
+     * APLIC for a TVM, only the IMSIC is used.
      */
-    if (!kvm_kernel_irqchip_split()) {
+    if (!kvm_kernel_irqchip_split() && !riscv_cove_vm_active()) {
         ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG,
                                 KVM_DEV_RISCV_AIA_CONFIG_SRCS,
                                 &aia_irq_num, true, NULL);
-- 
2.34.1