KVM: PPC: Accelerate H_PUT_TCE by implementing it in real mode
This improves I/O performance for guests using the PAPR
paravirtualization interface by making the H_PUT_TCE hcall faster, by
implementing it in real mode. H_PUT_TCE is used for updating virtual
IOMMU tables, and is used both for virtual I/O and for real I/O in the
PAPR interface.
Since this moves the IOMMU tables into the kernel, we define a new
KVM_CREATE_SPAPR_TCE ioctl to allow qemu to create the tables. The
ioctl returns a file descriptor which can be used to mmap the newly
created table. The qemu driver models use them in the same way as
userspace managed tables, but they can be updated directly by the
guest with a real-mode H_PUT_TCE implementation, reducing the number
of host/guest context switches during guest IO.
There are certain circumstances where it is useful for userland qemu
to write to the TCE table even if the kernel H_PUT_TCE path is used
most of the time. Specifically, allowing this will avoid awkwardness
when we need to reset the table. More importantly, we will in the
future need to write the table in order to restore its state after a
checkpoint resume or migration.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/arch/powerpc/include/asm/kvm.h b/arch/powerpc/include/asm/kvm.h
index d2ca5ed..c3ec990 100644
--- a/arch/powerpc/include/asm/kvm.h
+++ b/arch/powerpc/include/asm/kvm.h
@@ -22,6 +22,9 @@
#include <linux/types.h>
+/* Select powerpc specific features in <linux/kvm.h> */
+#define __KVM_HAVE_SPAPR_TCE
+
struct kvm_regs {
__u64 pc;
__u64 cr;
@@ -272,4 +275,10 @@
#define KVM_INTERRUPT_UNSET -2U
#define KVM_INTERRUPT_SET_LEVEL -3U
+/* for KVM_CAP_SPAPR_TCE */
+struct kvm_create_spapr_tce {
+ __u64 liobn;
+ __u32 window_size;
+};
+
#endif /* __LINUX_KVM_POWERPC_H */
diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 5f73388..e43fe42 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -27,4 +27,6 @@
}
#endif
+#define SPAPR_TCE_SHIFT 12
+
#endif /* __ASM_KVM_BOOK3S_64_H__ */
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 6ebf172..5616e39 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -144,6 +144,14 @@
atomic_t refcnt;
};
+struct kvmppc_spapr_tce_table {
+ struct list_head list;
+ struct kvm *kvm;
+ u64 liobn;
+ u32 window_size;
+ struct page *pages[0];
+};
+
struct kvm_arch {
#ifdef CONFIG_KVM_BOOK3S_64_HV
unsigned long hpt_virt;
@@ -157,6 +165,7 @@
unsigned long sdr1;
unsigned long host_sdr1;
int tlbie_lock;
+ struct list_head spapr_tce_tables;
unsigned short last_vcpu[NR_CPUS];
#endif /* CONFIG_KVM_BOOK3S_64_HV */
};
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 2afe92e..99f6fcf 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -119,6 +119,8 @@
extern void kvmppc_map_vrma(struct kvm *kvm,
struct kvm_userspace_memory_region *mem);
extern int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu);
+extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
+ struct kvm_create_spapr_tce *args);
extern int kvmppc_core_init_vm(struct kvm *kvm);
extern void kvmppc_core_destroy_vm(struct kvm *kvm);
extern int kvmppc_core_prepare_memory_region(struct kvm *kvm,