KVM: PPC: Implement MMIO emulation support for Book3S HV guests

This provides the low-level support for MMIO emulation in Book3S HV
guests.  When the guest tries to map a page which is not covered by
any memslot, that page is taken to be an MMIO emulation page.  Instead
of inserting a valid HPTE, we insert an HPTE that has the valid bit
clear but another hypervisor software-use bit set, which we call
HPTE_V_ABSENT, to indicate that this is an absent page.  An
absent page is treated much like a valid page as far as guest hcalls
(H_ENTER, H_REMOVE, H_READ etc.) are concerned, except of course that
an absent HPTE doesn't need to be invalidated with tlbie since it
was never valid as far as the hardware is concerned.

When the guest accesses a page for which there is an absent HPTE, it
will take a hypervisor data storage interrupt (HDSI) since we now set
the VPM1 bit in the LPCR.  Our HDSI handler for HPTE-not-present faults
looks up the hash table and if it finds an absent HPTE mapping the
requested virtual address, will switch to kernel mode and handle the
fault in kvmppc_book3s_hv_page_fault(), which at present just calls
kvmppc_hv_emulate_mmio() to set up the MMIO emulation.

This is based on an earlier patch by Benjamin Herrenschmidt, but since
heavily reworked.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 9508c03..79dc37f 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -43,12 +43,15 @@ static inline void svcpu_put(struct kvmppc_book3s_shadow_vcpu *svcpu)
 #define HPT_HASH_MASK	(HPT_NPTEG - 1)
 #endif
 
+#define VRMA_VSID	0x1ffffffUL	/* 1TB VSID reserved for VRMA */
+
 /*
  * We use a lock bit in HPTE dword 0 to synchronize updates and
  * accesses to each HPTE, and another bit to indicate non-present
  * HPTEs.
  */
 #define HPTE_V_HVLOCK	0x40UL
+#define HPTE_V_ABSENT	0x20UL
 
 static inline long try_lock_hpte(unsigned long *hpte, unsigned long bits)
 {
@@ -144,6 +147,29 @@ static inline unsigned long hpte_cache_bits(unsigned long pte_val)
 #endif
 }
 
+static inline bool hpte_read_permission(unsigned long pp, unsigned long key)
+{
+	if (key)
+		return PP_RWRX <= pp && pp <= PP_RXRX;
+	return 1;
+}
+
+static inline bool hpte_write_permission(unsigned long pp, unsigned long key)
+{
+	if (key)
+		return pp == PP_RWRW;
+	return pp <= PP_RWRW;
+}
+
+static inline int hpte_get_skey_perm(unsigned long hpte_r, unsigned long amr)
+{
+	unsigned long skey;
+
+	skey = ((hpte_r & HPTE_R_KEY_HI) >> 57) |
+		((hpte_r & HPTE_R_KEY_LO) >> 9);
+	return (amr >> (62 - 2 * skey)) & 3;
+}
+
 static inline void lock_rmap(unsigned long *rmap)
 {
 	do {