powerpc: Disable relocation on exceptions whenever PR KVM is active

For PR KVM we allow userspace to map 0xc000000000000000. Because
transitioning from userspace to the guest kernel may use the relocated
exception vectors we have to disable relocation on exceptions whenever
PR KVM is active as we cannot trust that address.

This issue does not apply to HV KVM, since changing from a guest to the
hypervisor will never use the relocated exception vectors.

Currently the hypervisor interface only allows us to toggle relocation
on exceptions on a partition wide scope, so we need to globally disable
relocation on exceptions when the first PR KVM instance is started and
only re-enable them when all PR KVM instances have been destroyed.

It's a bit heavy handed, but until the hypervisor gives us a lightweight
way to toggle relocation on exceptions on a single thread it's only real
option.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 0975e5c0bb19f93f85cfc1b6552f4c405771ead4..4bc2c3dad6adf4045de3c9749c1c7fec1b777bb5 100644 (file)
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -395,6 +395,15 @@ static inline unsigned long cmo_get_page_size(void)
 {
        return CMO_PageSize;
 }
+
+extern long pSeries_enable_reloc_on_exc(void);
+extern long pSeries_disable_reloc_on_exc(void);
+
+#else
+
+#define pSeries_enable_reloc_on_exc()  do {} while (0)
+#define pSeries_disable_reloc_on_exc() do {} while (0)
+
 #endif /* CONFIG_PPC_PSERIES */
 
 #endif /* __ASSEMBLY__ */

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 28d38adeca73af0658785a79f94da7a7865ec854..67e4708388a00884ed1f34d759248ecafdbcb4da 100644 (file)
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -34,6 +34,7 @@
 #include <asm/kvm_book3s.h>
 #include <asm/mmu_context.h>
 #include <asm/switch_to.h>
+#include <asm/firmware.h>
 #include <linux/gfp.h>
 #include <linux/sched.h>
 #include <linux/vmalloc.h>
@@ -1284,12 +1285,21 @@ void kvmppc_core_flush_memslot(struct kvm *kvm, struct kvm_memory_slot *memslot)
 {
 }
 
+static unsigned int kvm_global_user_count = 0;
+static DEFINE_SPINLOCK(kvm_global_user_count_lock);
+
 int kvmppc_core_init_vm(struct kvm *kvm)
 {
 #ifdef CONFIG_PPC64
        INIT_LIST_HEAD(&kvm->arch.spapr_tce_tables);
 #endif
 
+       if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
+               spin_lock(&kvm_global_user_count_lock);
+               if (++kvm_global_user_count == 1)
+                       pSeries_disable_reloc_on_exc();
+               spin_unlock(&kvm_global_user_count_lock);
+       }
        return 0;
 }
 
@@ -1298,6 +1308,14 @@ void kvmppc_core_destroy_vm(struct kvm *kvm)
 #ifdef CONFIG_PPC64
        WARN_ON(!list_empty(&kvm->arch.spapr_tce_tables));
 #endif
+
+       if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
+               spin_lock(&kvm_global_user_count_lock);
+               BUG_ON(kvm_global_user_count == 0);
+               if (--kvm_global_user_count == 0)
+                       pSeries_enable_reloc_on_exc();
+               spin_unlock(&kvm_global_user_count_lock);
+       }
 }
 
 static int kvmppc_book3s_init(void)

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index ca55882465d6b0d027ef785f941c64a342985f99..1890730354bb23070452d3b9a111719e7cab5792 100644 (file)
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -375,7 +375,7 @@ static void pSeries_idle(void)
  * to ever be a problem in practice we can move this into a kernel thread to
  * finish off the process later in boot.
  */
-static int __init pSeries_enable_reloc_on_exc(void)
+long pSeries_enable_reloc_on_exc(void)
 {
        long rc;
        unsigned int delay, total_delay = 0;
@@ -397,9 +397,9 @@ static int __init pSeries_enable_reloc_on_exc(void)
                mdelay(delay);
        }
 }
+EXPORT_SYMBOL(pSeries_enable_reloc_on_exc);
 
-#ifdef CONFIG_KEXEC
-static long pSeries_disable_reloc_on_exc(void)
+long pSeries_disable_reloc_on_exc(void)
 {
        long rc;
 
@@ -410,7 +410,9 @@ static long pSeries_disable_reloc_on_exc(void)
                mdelay(get_longbusy_msecs(rc));
        }
 }
+EXPORT_SYMBOL(pSeries_disable_reloc_on_exc);
 
+#ifdef CONFIG_KEXEC
 static void pSeries_machine_kexec(struct kimage *image)
 {
        long rc;