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93b159b466
linux/arch/powerpc/kvm/book3s_64_mmu_host.c
Paul Mackerras 93b159b466 KVM: PPC: Book3S PR: Better handling of host-side read-only pages 
Currently we request write access to all pages that get mapped into the
guest, even if the guest is only loading from the page.  This reduces
the effectiveness of KSM because it means that we unshare every page we
access.  Also, we always set the changed (C) bit in the guest HPTE if
it allows writing, even for a guest load.

This fixes both these problems.  We pass an 'iswrite' flag to the
mmu.xlate() functions and to kvmppc_mmu_map_page() to indicate whether
the access is a load or a store.  The mmu.xlate() functions now only
set C for stores.  kvmppc_gfn_to_pfn() now calls gfn_to_pfn_prot()
instead of gfn_to_pfn() so that it can indicate whether we need write
access to the page, and get back a 'writable' flag to indicate whether
the page is writable or not.  If that 'writable' flag is clear, we then
make the host HPTE read-only even if the guest HPTE allowed writing.

This means that we can get a protection fault when the guest writes to a
page that it has mapped read-write but which is read-only on the host
side (perhaps due to KSM having merged the page).  Thus we now call
kvmppc_handle_pagefault() for protection faults as well as HPTE not found
faults.  In kvmppc_handle_pagefault(), if the access was allowed by the
guest HPTE and we thus need to install a new host HPTE, we then need to
remove the old host HPTE if there is one.  This is done with a new
function, kvmppc_mmu_unmap_page(), which uses kvmppc_mmu_pte_vflush() to
find and remove the old host HPTE.

Since the memslot-related functions require the KVM SRCU read lock to
be held, this adds srcu_read_lock/unlock pairs around the calls to
kvmppc_handle_pagefault().

Finally, this changes kvmppc_mmu_book3s_32_xlate_pte() to not ignore
guest HPTEs that don't permit access, and to return -EPERM for accesses
that are not permitted by the page protections.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
2013-10-17 14:49:35 +02:00

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/*
* Copyright (C) 2009 SUSE Linux Products GmbH. All rights reserved.
*
* Authors:
* Alexander Graf <agraf@suse.de>
* Kevin Wolf <mail@kevin-wolf.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <linux/kvm_host.h>
#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s.h>
#include <asm/mmu-hash64.h>
#include <asm/machdep.h>
#include <asm/mmu_context.h>
#include <asm/hw_irq.h>
#include "trace.h"
#define PTE_SIZE 12
void kvmppc_mmu_invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache *pte)
{
ppc_md.hpte_invalidate(pte->slot, pte->host_vpn,
pte->pagesize, pte->pagesize, MMU_SEGSIZE_256M,
false);
}
/* We keep 512 gvsid->hvsid entries, mapping the guest ones to the array using
* a hash, so we don't waste cycles on looping */
static u16 kvmppc_sid_hash(struct kvm_vcpu *vcpu, u64 gvsid)
{
return (u16)(((gvsid >> (SID_MAP_BITS * 7)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 6)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 5)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 4)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 3)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 2)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 1)) & SID_MAP_MASK) ^
((gvsid >> (SID_MAP_BITS * 0)) & SID_MAP_MASK));
}
static struct kvmppc_sid_map *find_sid_vsid(struct kvm_vcpu *vcpu, u64 gvsid)
{
struct kvmppc_sid_map *map;
u16 sid_map_mask;
if (vcpu->arch.shared->msr & MSR_PR)
gvsid |= VSID_PR;
sid_map_mask = kvmppc_sid_hash(vcpu, gvsid);
map = &to_book3s(vcpu)->sid_map[sid_map_mask];
if (map->valid && (map->guest_vsid == gvsid)) {
trace_kvm_book3s_slb_found(gvsid, map->host_vsid);
return map;
}
map = &to_book3s(vcpu)->sid_map[SID_MAP_MASK - sid_map_mask];
if (map->valid && (map->guest_vsid == gvsid)) {
trace_kvm_book3s_slb_found(gvsid, map->host_vsid);
return map;
}
trace_kvm_book3s_slb_fail(sid_map_mask, gvsid);
return NULL;
}
int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct kvmppc_pte *orig_pte,
bool iswrite)
{
unsigned long vpn;
pfn_t hpaddr;
ulong hash, hpteg;
u64 vsid;
int ret;
int rflags = 0x192;
int vflags = 0;
int attempt = 0;
struct kvmppc_sid_map *map;
int r = 0;
int hpsize = MMU_PAGE_4K;
bool writable;
/* Get host physical address for gpa */
hpaddr = kvmppc_gfn_to_pfn(vcpu, orig_pte->raddr >> PAGE_SHIFT,
iswrite, &writable);
if (is_error_noslot_pfn(hpaddr)) {
printk(KERN_INFO "Couldn't get guest page for gfn %lx!\n", orig_pte->eaddr);
r = -EINVAL;
goto out;
}
hpaddr <<= PAGE_SHIFT;
/* and write the mapping ea -> hpa into the pt */
vcpu->arch.mmu.esid_to_vsid(vcpu, orig_pte->eaddr >> SID_SHIFT, &vsid);
map = find_sid_vsid(vcpu, vsid);
if (!map) {
ret = kvmppc_mmu_map_segment(vcpu, orig_pte->eaddr);
WARN_ON(ret < 0);
map = find_sid_vsid(vcpu, vsid);
}
if (!map) {
printk(KERN_ERR "KVM: Segment map for 0x%llx (0x%lx) failed\n",
vsid, orig_pte->eaddr);
WARN_ON(true);
r = -EINVAL;
goto out;
}
vpn = hpt_vpn(orig_pte->eaddr, map->host_vsid, MMU_SEGSIZE_256M);
if (!orig_pte->may_write || !writable)
rflags |= HPTE_R_PP;
else
mark_page_dirty(vcpu->kvm, orig_pte->raddr >> PAGE_SHIFT);
if (!orig_pte->may_execute)
rflags |= HPTE_R_N;
else
kvmppc_mmu_flush_icache(hpaddr >> PAGE_SHIFT);
/*
* Use 64K pages if possible; otherwise, on 64K page kernels,
* we need to transfer 4 more bits from guest real to host real addr.
*/
if (vsid & VSID_64K)
hpsize = MMU_PAGE_64K;
else
hpaddr |= orig_pte->raddr & (~0xfffULL & ~PAGE_MASK);
hash = hpt_hash(vpn, mmu_psize_defs[hpsize].shift, MMU_SEGSIZE_256M);
map_again:
hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP);
/* In case we tried normal mapping already, let's nuke old entries */
if (attempt > 1)
if (ppc_md.hpte_remove(hpteg) < 0) {
r = -1;
goto out;
}
ret = ppc_md.hpte_insert(hpteg, vpn, hpaddr, rflags, vflags,
hpsize, hpsize, MMU_SEGSIZE_256M);
if (ret < 0) {
/* If we couldn't map a primary PTE, try a secondary */
hash = ~hash;
vflags ^= HPTE_V_SECONDARY;
attempt++;
goto map_again;
} else {
struct hpte_cache *pte = kvmppc_mmu_hpte_cache_next(vcpu);
trace_kvm_book3s_64_mmu_map(rflags, hpteg,
vpn, hpaddr, orig_pte);
/* The ppc_md code may give us a secondary entry even though we
asked for a primary. Fix up. */
if ((ret & _PTEIDX_SECONDARY) && !(vflags & HPTE_V_SECONDARY)) {
hash = ~hash;
hpteg = ((hash & htab_hash_mask) * HPTES_PER_GROUP);
}
pte->slot = hpteg + (ret & 7);
pte->host_vpn = vpn;
pte->pte = *orig_pte;
pte->pfn = hpaddr >> PAGE_SHIFT;
pte->pagesize = hpsize;
kvmppc_mmu_hpte_cache_map(vcpu, pte);
}
kvm_release_pfn_clean(hpaddr >> PAGE_SHIFT);
out:
return r;
}
void kvmppc_mmu_unmap_page(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte)
{
u64 mask = 0xfffffffffULL;
u64 vsid;
vcpu->arch.mmu.esid_to_vsid(vcpu, pte->eaddr >> SID_SHIFT, &vsid);
if (vsid & VSID_64K)
mask = 0xffffffff0ULL;
kvmppc_mmu_pte_vflush(vcpu, pte->vpage, mask);
}
static struct kvmppc_sid_map *create_sid_map(struct kvm_vcpu *vcpu, u64 gvsid)
{
struct kvmppc_sid_map *map;
struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
u16 sid_map_mask;
static int backwards_map = 0;
if (vcpu->arch.shared->msr & MSR_PR)
gvsid |= VSID_PR;
/* We might get collisions that trap in preceding order, so let's
map them differently */
sid_map_mask = kvmppc_sid_hash(vcpu, gvsid);
if (backwards_map)
sid_map_mask = SID_MAP_MASK - sid_map_mask;
map = &to_book3s(vcpu)->sid_map[sid_map_mask];
/* Make sure we're taking the other map next time */
backwards_map = !backwards_map;
/* Uh-oh ... out of mappings. Let's flush! */
if (vcpu_book3s->proto_vsid_next == vcpu_book3s->proto_vsid_max) {
vcpu_book3s->proto_vsid_next = vcpu_book3s->proto_vsid_first;
memset(vcpu_book3s->sid_map, 0,
sizeof(struct kvmppc_sid_map) * SID_MAP_NUM);
kvmppc_mmu_pte_flush(vcpu, 0, 0);
kvmppc_mmu_flush_segments(vcpu);
}
map->host_vsid = vsid_scramble(vcpu_book3s->proto_vsid_next++, 256M);
map->guest_vsid = gvsid;
map->valid = true;
trace_kvm_book3s_slb_map(sid_map_mask, gvsid, map->host_vsid);
return map;
}
static int kvmppc_mmu_next_segment(struct kvm_vcpu *vcpu, ulong esid)
{
struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
int i;
int max_slb_size = 64;
int found_inval = -1;
int r;
if (!svcpu->slb_max)
svcpu->slb_max = 1;
/* Are we overwriting? */
for (i = 1; i < svcpu->slb_max; i++) {
if (!(svcpu->slb[i].esid & SLB_ESID_V))
found_inval = i;
else if ((svcpu->slb[i].esid & ESID_MASK) == esid) {
r = i;
goto out;
}
}
/* Found a spare entry that was invalidated before */
if (found_inval > 0) {
r = found_inval;
goto out;
}
/* No spare invalid entry, so create one */
if (mmu_slb_size < 64)
max_slb_size = mmu_slb_size;
/* Overflowing -> purge */
if ((svcpu->slb_max) == max_slb_size)
kvmppc_mmu_flush_segments(vcpu);
r = svcpu->slb_max;
svcpu->slb_max++;
out:
svcpu_put(svcpu);
return r;
}
int kvmppc_mmu_map_segment(struct kvm_vcpu *vcpu, ulong eaddr)
{
struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
u64 esid = eaddr >> SID_SHIFT;
u64 slb_esid = (eaddr & ESID_MASK) | SLB_ESID_V;
u64 slb_vsid = SLB_VSID_USER;
u64 gvsid;
int slb_index;
struct kvmppc_sid_map *map;
int r = 0;
slb_index = kvmppc_mmu_next_segment(vcpu, eaddr & ESID_MASK);
if (vcpu->arch.mmu.esid_to_vsid(vcpu, esid, &gvsid)) {
/* Invalidate an entry */
svcpu->slb[slb_index].esid = 0;
r = -ENOENT;
goto out;
}
map = find_sid_vsid(vcpu, gvsid);
if (!map)
map = create_sid_map(vcpu, gvsid);
map->guest_esid = esid;
slb_vsid |= (map->host_vsid << 12);
slb_vsid &= ~SLB_VSID_KP;
slb_esid |= slb_index;
#ifdef CONFIG_PPC_64K_PAGES
/* Set host segment base page size to 64K if possible */
if (gvsid & VSID_64K)
slb_vsid |= mmu_psize_defs[MMU_PAGE_64K].sllp;
#endif
svcpu->slb[slb_index].esid = slb_esid;
svcpu->slb[slb_index].vsid = slb_vsid;
trace_kvm_book3s_slbmte(slb_vsid, slb_esid);
out:
svcpu_put(svcpu);
return r;
}
void kvmppc_mmu_flush_segment(struct kvm_vcpu *vcpu, ulong ea, ulong seg_size)
{
struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
ulong seg_mask = -seg_size;
int i;
for (i = 1; i < svcpu->slb_max; i++) {
if ((svcpu->slb[i].esid & SLB_ESID_V) &&
(svcpu->slb[i].esid & seg_mask) == ea) {
/* Invalidate this entry */
svcpu->slb[i].esid = 0;
}
}
svcpu_put(svcpu);
}
void kvmppc_mmu_flush_segments(struct kvm_vcpu *vcpu)
{
struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
svcpu->slb_max = 1;
svcpu->slb[0].esid = 0;
svcpu_put(svcpu);
}
void kvmppc_mmu_destroy(struct kvm_vcpu *vcpu)
{
kvmppc_mmu_hpte_destroy(vcpu);
__destroy_context(to_book3s(vcpu)->context_id[0]);
}
int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
{
struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu);
int err;
err = __init_new_context();
if (err < 0)
return -1;
vcpu3s->context_id[0] = err;
vcpu3s->proto_vsid_max = ((u64)(vcpu3s->context_id[0] + 1)
<< ESID_BITS) - 1;
vcpu3s->proto_vsid_first = (u64)vcpu3s->context_id[0] << ESID_BITS;
vcpu3s->proto_vsid_next = vcpu3s->proto_vsid_first;
kvmppc_mmu_hpte_init(vcpu);
return 0;
}
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