[S390] Use gmap translation for accessing guest memory

This patch removes kvm-s390 internal assumption of a linear mapping
of guest address space to user space. Previously, guest memory was
translated to user addresses using a fixed offset (gmsor). The new
code uses gmap_fault to resolve guest addresses.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

6 files changed, 194 insertions, 110 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 8264b0b0f1ce..e5d082c4f3aa 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -93,9 +93,7 @@ struct kvm_s390_sie_block {
         __u32   scaol;                  /* 0x0064 */
         __u8    reserved68[4];          /* 0x0068 */
         __u32   todpr;                  /* 0x006c */
-        __u8    reserved70[16];         /* 0x0070 */
-        __u64   gmsor;                  /* 0x0080 */
-        __u64   gmslm;                  /* 0x0088 */
+        __u8    reserved70[32];         /* 0x0070 */
         psw_t   gpsw;                   /* 0x0090 */
         __u64   gg14;                   /* 0x00a0 */
         __u64   gg15;                   /* 0x00a8 */
diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
index 03c716a0f01f..c86f6ae43f76 100644
--- a/arch/s390/kvm/gaccess.h
+++ b/arch/s390/kvm/gaccess.h
@@ -1,5 +1,5 @@
 /*
- * gaccess.h -  access guest memory
+ * access.h -  access guest memory
  *
  * Copyright IBM Corp. 2008,2009
  *
@@ -22,20 +22,13 @@ static inline void __user *__guestaddr_to_user(struct kvm_vcpu *vcpu,
                                                unsigned long guestaddr)
 {
         unsigned long prefix  = vcpu->arch.sie_block->prefix;
-        unsigned long origin  = vcpu->arch.sie_block->gmsor;
-        unsigned long memsize = kvm_s390_vcpu_get_memsize(vcpu);
 
         if (guestaddr < 2 * PAGE_SIZE)
                 guestaddr += prefix;
         else if ((guestaddr >= prefix) && (guestaddr < prefix + 2 * PAGE_SIZE))
                 guestaddr -= prefix;
 
-        if (guestaddr > memsize)
-                return (void __user __force *) ERR_PTR(-EFAULT);
-
-        guestaddr += origin;
-
-        return (void __user *) guestaddr;
+        return (void __user *) gmap_fault(guestaddr, vcpu->arch.gmap);
 }
 
 static inline int get_guest_u64(struct kvm_vcpu *vcpu, unsigned long guestaddr,
@@ -141,11 +134,11 @@ static inline int put_guest_u8(struct kvm_vcpu *vcpu, unsigned long guestaddr,
 
 static inline int __copy_to_guest_slow(struct kvm_vcpu *vcpu,
                                        unsigned long guestdest,
-                                       const void *from, unsigned long n)
+                                       void *from, unsigned long n)
 {
         int rc;
         unsigned long i;
-        const u8 *data = from;
+        u8 *data = from;
 
         for (i = 0; i < n; i++) {
                 rc = put_guest_u8(vcpu, guestdest++, *(data++));
@@ -155,12 +148,95 @@ static inline int __copy_to_guest_slow(struct kvm_vcpu *vcpu,
         return 0;
 }
 
+static inline int __copy_to_guest_fast(struct kvm_vcpu *vcpu,
+                                       unsigned long guestdest,
+                                       void *from, unsigned long n)
+{
+        int r;
+        void __user *uptr;
+        unsigned long size;
+
+        if (guestdest + n < guestdest)
+                return -EFAULT;
+
+        /* simple case: all within one segment table entry? */
+        if ((guestdest & PMD_MASK) == ((guestdest+n) & PMD_MASK)) {
+                uptr = (void __user *) gmap_fault(guestdest, vcpu->arch.gmap);
+
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
+
+                r = copy_to_user(uptr, from, n);
+
+                if (r)
+                        r = -EFAULT;
+
+                goto out;
+        }
+
+        /* copy first segment */
+        uptr = (void __user *)gmap_fault(guestdest, vcpu->arch.gmap);
+
+        if (IS_ERR((void __force *) uptr))
+                return PTR_ERR((void __force *) uptr);
+
+        size = PMD_SIZE - (guestdest & ~PMD_MASK);
+
+        r = copy_to_user(uptr, from, size);
+
+        if (r) {
+                r = -EFAULT;
+                goto out;
+        }
+        from += size;
+        n -= size;
+        guestdest += size;
+
+        /* copy full segments */
+        while (n >= PMD_SIZE) {
+                uptr = (void __user *)gmap_fault(guestdest, vcpu->arch.gmap);
+
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
+
+                r = copy_to_user(uptr, from, PMD_SIZE);
+
+                if (r) {
+                        r = -EFAULT;
+                        goto out;
+                }
+                from += PMD_SIZE;
+                n -= PMD_SIZE;
+                guestdest += PMD_SIZE;
+        }
+
+        /* copy the tail segment */
+        if (n) {
+                uptr = (void __user *)gmap_fault(guestdest, vcpu->arch.gmap);
+
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
+
+                r = copy_to_user(uptr, from, n);
+
+                if (r)
+                        r = -EFAULT;
+        }
+out:
+        return r;
+}
+
+static inline int copy_to_guest_absolute(struct kvm_vcpu *vcpu,
+                                         unsigned long guestdest,
+                                         void *from, unsigned long n)
+{
+        return __copy_to_guest_fast(vcpu, guestdest, from, n);
+}
+
 static inline int copy_to_guest(struct kvm_vcpu *vcpu, unsigned long guestdest,
-                                const void *from, unsigned long n)
+                                void *from, unsigned long n)
 {
         unsigned long prefix  = vcpu->arch.sie_block->prefix;
-        unsigned long origin  = vcpu->arch.sie_block->gmsor;
-        unsigned long memsize = kvm_s390_vcpu_get_memsize(vcpu);
 
         if ((guestdest < 2 * PAGE_SIZE) && (guestdest + n > 2 * PAGE_SIZE))
                 goto slowpath;
@@ -177,15 +253,7 @@ static inline int copy_to_guest(struct kvm_vcpu *vcpu, unsigned long guestdest,
         else if ((guestdest >= prefix) && (guestdest < prefix + 2 * PAGE_SIZE))
                 guestdest -= prefix;
 
-        if (guestdest + n > memsize)
-                return -EFAULT;
-
-        if (guestdest + n < guestdest)
-                return -EFAULT;
-
-        guestdest += origin;
-
-        return copy_to_user((void __user *) guestdest, from, n);
+        return __copy_to_guest_fast(vcpu, guestdest, from, n);
 slowpath:
         return __copy_to_guest_slow(vcpu, guestdest, from, n);
 }
@@ -206,74 +274,113 @@ static inline int __copy_from_guest_slow(struct kvm_vcpu *vcpu, void *to,
         return 0;
 }
 
-static inline int copy_from_guest(struct kvm_vcpu *vcpu, void *to,
-                                  unsigned long guestsrc, unsigned long n)
+static inline int __copy_from_guest_fast(struct kvm_vcpu *vcpu, void *to,
+                                         unsigned long guestsrc,
+                                         unsigned long n)
 {
-        unsigned long prefix  = vcpu->arch.sie_block->prefix;
-        unsigned long origin  = vcpu->arch.sie_block->gmsor;
-        unsigned long memsize = kvm_s390_vcpu_get_memsize(vcpu);
+        int r;
+        void __user *uptr;
+        unsigned long size;
 
-        if ((guestsrc < 2 * PAGE_SIZE) && (guestsrc + n > 2 * PAGE_SIZE))
-                goto slowpath;
+        if (guestsrc + n < guestsrc)
+                return -EFAULT;
 
-        if ((guestsrc < prefix) && (guestsrc + n > prefix))
-                goto slowpath;
+        /* simple case: all within one segment table entry? */
+        if ((guestsrc & PMD_MASK) == ((guestsrc+n) & PMD_MASK)) {
+                uptr = (void __user *) gmap_fault(guestsrc, vcpu->arch.gmap);
 
-        if ((guestsrc < prefix + 2 * PAGE_SIZE)
-            && (guestsrc + n > prefix + 2 * PAGE_SIZE))
-                goto slowpath;
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
 
-        if (guestsrc < 2 * PAGE_SIZE)
-                guestsrc += prefix;
-        else if ((guestsrc >= prefix) && (guestsrc < prefix + 2 * PAGE_SIZE))
-                guestsrc -= prefix;
+                r = copy_from_user(to, uptr, n);
 
-        if (guestsrc + n > memsize)
-                return -EFAULT;
+                if (r)
+                        r = -EFAULT;
 
-        if (guestsrc + n < guestsrc)
-                return -EFAULT;
+                goto out;
+        }
 
-        guestsrc += origin;
+        /* copy first segment */
+        uptr = (void __user *)gmap_fault(guestsrc, vcpu->arch.gmap);
 
-        return copy_from_user(to, (void __user *) guestsrc, n);
-slowpath:
-        return __copy_from_guest_slow(vcpu, to, guestsrc, n);
-}
+        if (IS_ERR((void __force *) uptr))
+                return PTR_ERR((void __force *) uptr);
 
-static inline int copy_to_guest_absolute(struct kvm_vcpu *vcpu,
-                                         unsigned long guestdest,
-                                         const void *from, unsigned long n)
-{
-        unsigned long origin  = vcpu->arch.sie_block->gmsor;
-        unsigned long memsize = kvm_s390_vcpu_get_memsize(vcpu);
+        size = PMD_SIZE - (guestsrc & ~PMD_MASK);
 
-        if (guestdest + n > memsize)
-                return -EFAULT;
+        r = copy_from_user(to, uptr, size);
 
-        if (guestdest + n < guestdest)
-                return -EFAULT;
+        if (r) {
+                r = -EFAULT;
+                goto out;
+        }
+        to += size;
+        n -= size;
+        guestsrc += size;
+
+        /* copy full segments */
+        while (n >= PMD_SIZE) {
+                uptr = (void __user *)gmap_fault(guestsrc, vcpu->arch.gmap);
+
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
+
+                r = copy_from_user(to, uptr, PMD_SIZE);
+
+                if (r) {
+                        r = -EFAULT;
+                        goto out;
+                }
+                to += PMD_SIZE;
+                n -= PMD_SIZE;
+                guestsrc += PMD_SIZE;
+        }
+
+        /* copy the tail segment */
+        if (n) {
+                uptr = (void __user *)gmap_fault(guestsrc, vcpu->arch.gmap);
 
-        guestdest += origin;
+                if (IS_ERR((void __force *) uptr))
+                        return PTR_ERR((void __force *) uptr);
 
-        return copy_to_user((void __user *) guestdest, from, n);
+                r = copy_from_user(to, uptr, n);
+
+                if (r)
+                        r = -EFAULT;
+        }
+out:
+        return r;
 }
 
 static inline int copy_from_guest_absolute(struct kvm_vcpu *vcpu, void *to,
                                            unsigned long guestsrc,
                                            unsigned long n)
 {
-        unsigned long origin  = vcpu->arch.sie_block->gmsor;
-        unsigned long memsize = kvm_s390_vcpu_get_memsize(vcpu);
+        return __copy_from_guest_fast(vcpu, to, guestsrc, n);
+}
 
-        if (guestsrc + n > memsize)
-                return -EFAULT;
+static inline int copy_from_guest(struct kvm_vcpu *vcpu, void *to,
+                                  unsigned long guestsrc, unsigned long n)
+{
+        unsigned long prefix  = vcpu->arch.sie_block->prefix;
 
-        if (guestsrc + n < guestsrc)
-                return -EFAULT;
+        if ((guestsrc < 2 * PAGE_SIZE) && (guestsrc + n > 2 * PAGE_SIZE))
+                goto slowpath;
 
-        guestsrc += origin;
+        if ((guestsrc < prefix) && (guestsrc + n > prefix))
+                goto slowpath;
+
+        if ((guestsrc < prefix + 2 * PAGE_SIZE)
+            && (guestsrc + n > prefix + 2 * PAGE_SIZE))
+                goto slowpath;
+
+        if (guestsrc < 2 * PAGE_SIZE)
+                guestsrc += prefix;
+        else if ((guestsrc >= prefix) && (guestsrc < prefix + 2 * PAGE_SIZE))
+                guestsrc -= prefix;
 
-        return copy_from_user(to, (void __user *) guestsrc, n);
+        return __copy_from_guest_fast(vcpu, to, guestsrc, n);
+slowpath:
+        return __copy_from_guest_slow(vcpu, to, guestsrc, n);
 }
 #endif
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 654fc1fa37e7..c7c51898984e 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -165,26 +165,30 @@ static int handle_validity(struct kvm_vcpu *vcpu)
         int rc;
 
         vcpu->stat.exit_validity++;
-        if ((viwhy == 0x37) && (vcpu->arch.sie_block->prefix
-                <= kvm_s390_vcpu_get_memsize(vcpu) - 2*PAGE_SIZE)) {
-                rc = fault_in_pages_writeable((char __user *)
-                         vcpu->arch.sie_block->gmsor +
-                         vcpu->arch.sie_block->prefix,
-                         2*PAGE_SIZE);
+        if (viwhy == 0x37) {
+                vmaddr = gmap_fault(vcpu->arch.sie_block->prefix,
+                                    vcpu->arch.gmap);
+                if (IS_ERR_VALUE(vmaddr)) {
+                        rc = -EOPNOTSUPP;
+                        goto out;
+                }
+                rc = fault_in_pages_writeable((char __user *) vmaddr,
+                         PAGE_SIZE);
                 if (rc) {
                         /* user will receive sigsegv, exit to user */
                         rc = -EOPNOTSUPP;
                         goto out;
                 }
-                vmaddr = gmap_fault(vcpu->arch.sie_block->prefix,
+                vmaddr = gmap_fault(vcpu->arch.sie_block->prefix + PAGE_SIZE,
                                     vcpu->arch.gmap);
                 if (IS_ERR_VALUE(vmaddr)) {
                         rc = -EOPNOTSUPP;
                         goto out;
                 }
-                vmaddr = gmap_fault(vcpu->arch.sie_block->prefix + PAGE_SIZE,
-                                    vcpu->arch.gmap);
-                if (IS_ERR_VALUE(vmaddr)) {
+                rc = fault_in_pages_writeable((char __user *) vmaddr,
+                         PAGE_SIZE);
+                if (rc) {
+                        /* user will receive sigsegv, exit to user */
                         rc = -EOPNOTSUPP;
                         goto out;
                 }
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3ebb4ba83d9d..5a99f342fd0b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -549,7 +549,7 @@ rerun_vcpu:
         return rc;
 }
 
-static int __guestcopy(struct kvm_vcpu *vcpu, u64 guestdest, const void *from,
+static int __guestcopy(struct kvm_vcpu *vcpu, u64 guestdest, void *from,
                        unsigned long n, int prefix)
 {
         if (prefix)
@@ -566,7 +566,7 @@ static int __guestcopy(struct kvm_vcpu *vcpu, u64 guestdest, const void *from,
  */
 int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr)
 {
-        const unsigned char archmode = 1;
+        unsigned char archmode = 1;
         int prefix;
 
         if (addr == KVM_S390_STORE_STATUS_NOADDR) {
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 65e2201a555b..63e5190776e9 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -58,31 +58,8 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
 int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code);
 int kvm_s390_inject_sigp_stop(struct kvm_vcpu *vcpu, int action);
 
-static inline long kvm_s390_vcpu_get_memsize(struct kvm_vcpu *vcpu)
-{
-        return vcpu->arch.sie_block->gmslm
-                - vcpu->arch.sie_block->gmsor
-                - VIRTIODESCSPACE + 1ul;
-}
-
 static inline void kvm_s390_vcpu_set_mem(struct kvm_vcpu *vcpu)
 {
-        int idx;
-        struct kvm_memory_slot *mem;
-        struct kvm_memslots *memslots;
-
-        idx = srcu_read_lock(&vcpu->kvm->srcu);
-        memslots = kvm_memslots(vcpu->kvm);
-
-        mem = &memslots->memslots[0];
-
-        vcpu->arch.sie_block->gmsor = mem->userspace_addr;
-        vcpu->arch.sie_block->gmslm =
-                mem->userspace_addr +
-                (mem->npages << PAGE_SHIFT) +
-                VIRTIODESCSPACE - 1ul;
-
-        srcu_read_unlock(&vcpu->kvm->srcu, idx);
 }
 
 /* implemented in priv.c */
diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index 702276f5e2fa..d6a50c1fb2e6 100644
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -189,10 +189,8 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, u16 cpu_addr, u32 address,
 
         /* make sure that the new value is valid memory */
         address = address & 0x7fffe000u;
-        if ((copy_from_user(&tmp, (void __user *)
-                (address + vcpu->arch.sie_block->gmsor) , 1)) ||
-           (copy_from_user(&tmp, (void __user *)(address +
-                        vcpu->arch.sie_block->gmsor + PAGE_SIZE), 1))) {
+        if (copy_from_guest_absolute(vcpu, &tmp, address, 1) ||
+           copy_from_guest_absolute(vcpu, &tmp, address + PAGE_SIZE, 1)) {
                 *reg |= SIGP_STAT_INVALID_PARAMETER;
                 return 1; /* invalid parameter */
         }