diff mbox series

[PULL,25/32] target/arm/kvm: Drop support for kernels without KVM_ARM_PREFERRED_TARGET

Message ID 20250506144214.1221450-26-peter.maydell@linaro.org
State New
Headers show
Series [PULL,01/32] hw/arm/npcm8xx_boards: Correct valid_cpu_types setting of NPCM8XX SoC | expand

Commit Message

Peter Maydell May 6, 2025, 2:42 p.m. UTC 
Our KVM code includes backwards compatibility support for ancient
kernels which don't support the KVM_ARM_PREFERRED_TARGET ioctl.  This
ioctl was introduced in kernel commit 42c4e0c77ac91 in September
2013 and is in v3.12, so it's reasonable to assume it's present.

(We already dropped support for kernels without KVM_CAP_DEVICE_CTRL,
a feature added to the kernel in April 2013, in our commit
84f298ea3e; so there are only about six months' worth of kernels,
from v3.9 to v3.11, that we don't already fail to run on and that
this commit is dropping handling for.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250318114222.1018200-1-peter.maydell@linaro.org
---
 target/arm/kvm_arm.h      |  7 +----
 target/arm/arm-qmp-cmds.c |  2 +-
 target/arm/kvm.c          | 55 ++++++---------------------------------
 3 files changed, 10 insertions(+), 54 deletions(-)
diff mbox series

Patch

diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index 05c3de8cd46..5f17fc2f3d5 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -97,10 +97,6 @@  void kvm_arm_reset_vcpu(ARMCPU *cpu);
 #ifdef CONFIG_KVM
 /**
  * kvm_arm_create_scratch_host_vcpu:
- * @cpus_to_try: array of QEMU_KVM_ARM_TARGET_* values (terminated with
- * QEMU_KVM_ARM_TARGET_NONE) to try as fallback if the kernel does not
- * know the PREFERRED_TARGET ioctl. Passing NULL is the same as passing
- * an empty array.
  * @fdarray: filled in with kvmfd, vmfd, cpufd file descriptors in that order
  * @init: filled in with the necessary values for creating a host
  * vcpu. If NULL is provided, will not init the vCPU (though the cpufd
@@ -113,8 +109,7 @@  void kvm_arm_reset_vcpu(ARMCPU *cpu);
  * Returns: true on success (and fdarray and init are filled in),
  * false on failure (and fdarray and init are not valid).
  */
-bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
-                                      int *fdarray,
+bool kvm_arm_create_scratch_host_vcpu(int *fdarray,
                                       struct kvm_vcpu_init *init);
 
 /**
diff --git a/target/arm/arm-qmp-cmds.c b/target/arm/arm-qmp-cmds.c
index 883c0a0e8cc..a1a944adb43 100644
--- a/target/arm/arm-qmp-cmds.c
+++ b/target/arm/arm-qmp-cmds.c
@@ -46,7 +46,7 @@  static inline void gic_cap_kvm_probe(GICCapability *v2, GICCapability *v3)
 #ifdef CONFIG_KVM
     int fdarray[3];
 
-    if (!kvm_arm_create_scratch_host_vcpu(NULL, fdarray, NULL)) {
+    if (!kvm_arm_create_scratch_host_vcpu(fdarray, NULL)) {
         return;
     }
 
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 97de8c7e939..9c62d12b233 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -100,8 +100,7 @@  static int kvm_arm_vcpu_finalize(ARMCPU *cpu, int feature)
     return kvm_vcpu_ioctl(CPU(cpu), KVM_ARM_VCPU_FINALIZE, &feature);
 }
 
-bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
-                                      int *fdarray,
+bool kvm_arm_create_scratch_host_vcpu(int *fdarray,
                                       struct kvm_vcpu_init *init)
 {
     int ret = 0, kvmfd = -1, vmfd = -1, cpufd = -1;
@@ -150,40 +149,13 @@  bool kvm_arm_create_scratch_host_vcpu(const uint32_t *cpus_to_try,
         struct kvm_vcpu_init preferred;
 
         ret = ioctl(vmfd, KVM_ARM_PREFERRED_TARGET, &preferred);
-        if (!ret) {
-            init->target = preferred.target;
+        if (ret < 0) {
+            goto err;
         }
+        init->target = preferred.target;
     }
-    if (ret >= 0) {
-        ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, init);
-        if (ret < 0) {
-            goto err;
-        }
-    } else if (cpus_to_try) {
-        /* Old kernel which doesn't know about the
-         * PREFERRED_TARGET ioctl: we know it will only support
-         * creating one kind of guest CPU which is its preferred
-         * CPU type.
-         */
-        struct kvm_vcpu_init try;
-
-        while (*cpus_to_try != QEMU_KVM_ARM_TARGET_NONE) {
-            try.target = *cpus_to_try++;
-            memcpy(try.features, init->features, sizeof(init->features));
-            ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, &try);
-            if (ret >= 0) {
-                break;
-            }
-        }
-        if (ret < 0) {
-            goto err;
-        }
-        init->target = try.target;
-    } else {
-        /* Treat a NULL cpus_to_try argument the same as an empty
-         * list, which means we will fail the call since this must
-         * be an old kernel which doesn't support PREFERRED_TARGET.
-         */
+    ret = ioctl(cpufd, KVM_ARM_VCPU_INIT, init);
+    if (ret < 0) {
         goto err;
     }
 
@@ -259,17 +231,6 @@  static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
     uint64_t features = 0;
     int err;
 
-    /* Old kernels may not know about the PREFERRED_TARGET ioctl: however
-     * we know these will only support creating one kind of guest CPU,
-     * which is its preferred CPU type. Fortunately these old kernels
-     * support only a very limited number of CPUs.
-     */
-    static const uint32_t cpus_to_try[] = {
-        KVM_ARM_TARGET_AEM_V8,
-        KVM_ARM_TARGET_FOUNDATION_V8,
-        KVM_ARM_TARGET_CORTEX_A57,
-        QEMU_KVM_ARM_TARGET_NONE
-    };
     /*
      * target = -1 informs kvm_arm_create_scratch_host_vcpu()
      * to use the preferred target
@@ -300,7 +261,7 @@  static bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
         features |= 1ULL << ARM_FEATURE_PMU;
     }
 
-    if (!kvm_arm_create_scratch_host_vcpu(cpus_to_try, fdarray, &init)) {
+    if (!kvm_arm_create_scratch_host_vcpu(fdarray, &init)) {
         return false;
     }
 
@@ -1835,7 +1796,7 @@  uint32_t kvm_arm_sve_get_vls(ARMCPU *cpu)
 
         probed = true;
 
-        if (!kvm_arm_create_scratch_host_vcpu(NULL, fdarray, &init)) {
+        if (!kvm_arm_create_scratch_host_vcpu(fdarray, &init)) {
             error_report("failed to create scratch VCPU with SVE enabled");
             abort();
         }