KVM: PPC: Use KVM_CAP_PPC_AIL_MODE_3

Use KVM_CAP_PPC_AIL_MODE_3 to advertise the capability to set the AIL
resource mode to 3 with the H_SET_MODE hypercall. This capability
differs between processor types and KVM types (PR, HV, Nested HV), and
affects guest-visible behaviour.

QEMU will implement a cap-ail-mode-3 to control this behaviour[1], and
use the KVM CAP if available to determine KVM support[2].

[1] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00437.html
[2] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00439.html

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
[mpe: Rebase onto 93b71801a827 from kvm-ppc-cap-210 branch, add EXPORT_SYMBOL]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220222064727.2314380-4-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index d0d3dd5..a555fb7 100644 (file)
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -28,11 +28,13 @@ void setup_panic(void);
 #define ARCH_PANIC_TIMEOUT 180
 
 #ifdef CONFIG_PPC_PSERIES
+extern bool pseries_reloc_on_exception(void);
 extern bool pseries_enable_reloc_on_exc(void);
 extern void pseries_disable_reloc_on_exc(void);
 extern void pseries_big_endian_exceptions(void);
 void __init pseries_little_endian_exceptions(void);
 #else
+static inline bool pseries_reloc_on_exception(void) { return false; }
 static inline bool pseries_enable_reloc_on_exc(void) { return false; }
 static inline void pseries_disable_reloc_on_exc(void) {}
 static inline void pseries_big_endian_exceptions(void) {}

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 9772b17..875c30c 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -705,6 +705,23 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
                r = 1;
                break;
 #endif
+       case KVM_CAP_PPC_AIL_MODE_3:
+               r = 0;
+               /*
+                * KVM PR, POWER7, and some POWER9s don't support AIL=3 mode.
+                * The POWER9s can support it if the guest runs in hash mode,
+                * but QEMU doesn't necessarily query the capability in time.
+                */
+               if (hv_enabled) {
+                       if (kvmhv_on_pseries()) {
+                               if (pseries_reloc_on_exception())
+                                       r = 1;
+                       } else if (cpu_has_feature(CPU_FTR_ARCH_207S) &&
+                                 !cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
+                               r = 1;
+                       }
+               }
+               break;
        default:
                r = 0;
                break;

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 83a04d9..5bdbbe2 100644 (file)
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -353,6 +353,14 @@ static void pseries_lpar_idle(void)
        pseries_idle_epilog();
 }
 
+static bool pseries_reloc_on_exception_enabled;
+
+bool pseries_reloc_on_exception(void)
+{
+       return pseries_reloc_on_exception_enabled;
+}
+EXPORT_SYMBOL_GPL(pseries_reloc_on_exception);
+
 /*
  * Enable relocation on during exceptions. This has partition wide scope and
  * may take a while to complete, if it takes longer than one second we will
@@ -377,6 +385,7 @@ bool pseries_enable_reloc_on_exc(void)
                                        " on exceptions: %ld\n", rc);
                                return false;
                        }
+                       pseries_reloc_on_exception_enabled = true;
                        return true;
                }
 
@@ -404,7 +413,9 @@ void pseries_disable_reloc_on_exc(void)
                        break;
                mdelay(get_longbusy_msecs(rc));
        }
-       if (rc != H_SUCCESS)
+       if (rc == H_SUCCESS)
+               pseries_reloc_on_exception_enabled = false;
+       else
                pr_warn("Warning: Failed to disable relocation on exceptions: %ld\n",
                        rc);
 }