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linux/arch/powerpc/kvm/book3s_32_mmu.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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/*
* 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.
*
* Copyright SUSE Linux Products GmbH 2009
*
* Authors: Alexander Graf <agraf@suse.de>
*/
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/highmem.h>
#include <asm/tlbflush.h>
#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s.h>
/* #define DEBUG_MMU */
/* #define DEBUG_MMU_PTE */
/* #define DEBUG_MMU_PTE_IP 0xfff14c40 */
#ifdef DEBUG_MMU
#define dprintk(X...) printk(KERN_INFO X)
#else
#define dprintk(X...) do { } while(0)
#endif
#ifdef DEBUG_MMU_PTE
#define dprintk_pte(X...) printk(KERN_INFO X)
#else
#define dprintk_pte(X...) do { } while(0)
#endif
#define PTEG_FLAG_ACCESSED 0x00000100
#define PTEG_FLAG_DIRTY 0x00000080
#ifndef SID_SHIFT
#define SID_SHIFT 28
#endif
static inline bool check_debug_ip(struct kvm_vcpu *vcpu)
{
#ifdef DEBUG_MMU_PTE_IP
return vcpu->arch.pc == DEBUG_MMU_PTE_IP;
#else
return true;
#endif
}
static inline u32 sr_vsid(u32 sr_raw)
{
return sr_raw & 0x0fffffff;
}
static inline bool sr_valid(u32 sr_raw)
{
return (sr_raw & 0x80000000) ? false : true;
}
static inline bool sr_ks(u32 sr_raw)
{
return (sr_raw & 0x40000000) ? true: false;
}
static inline bool sr_kp(u32 sr_raw)
{
return (sr_raw & 0x20000000) ? true: false;
}
static inline bool sr_nx(u32 sr_raw)
{
return (sr_raw & 0x10000000) ? true: false;
}
static int kvmppc_mmu_book3s_32_xlate_bat(struct kvm_vcpu *vcpu, gva_t eaddr,
struct kvmppc_pte *pte, bool data,
bool iswrite);
static int kvmppc_mmu_book3s_32_esid_to_vsid(struct kvm_vcpu *vcpu, ulong esid,
u64 *vsid);
static u32 find_sr(struct kvm_vcpu *vcpu, gva_t eaddr)
{
return vcpu->arch.shared->sr[(eaddr >> 28) & 0xf];
}
static u64 kvmppc_mmu_book3s_32_ea_to_vp(struct kvm_vcpu *vcpu, gva_t eaddr,
bool data)
{
u64 vsid;
struct kvmppc_pte pte;
if (!kvmppc_mmu_book3s_32_xlate_bat(vcpu, eaddr, &pte, data, false))
return pte.vpage;
kvmppc_mmu_book3s_32_esid_to_vsid(vcpu, eaddr >> SID_SHIFT, &vsid);
return (((u64)eaddr >> 12) & 0xffff) | (vsid << 16);
}
static void kvmppc_mmu_book3s_32_reset_msr(struct kvm_vcpu *vcpu)
{
kvmppc_set_msr(vcpu, 0);
}
static hva_t kvmppc_mmu_book3s_32_get_pteg(struct kvm_vcpu *vcpu,
u32 sre, gva_t eaddr,
bool primary)
{
struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
u32 page, hash, pteg, htabmask;
hva_t r;
page = (eaddr & 0x0FFFFFFF) >> 12;
htabmask = ((vcpu_book3s->sdr1 & 0x1FF) << 16) | 0xFFC0;
hash = ((sr_vsid(sre) ^ page) << 6);
if (!primary)
hash = ~hash;
hash &= htabmask;
pteg = (vcpu_book3s->sdr1 & 0xffff0000) | hash;
dprintk("MMU: pc=0x%lx eaddr=0x%lx sdr1=0x%llx pteg=0x%x vsid=0x%x\n",
kvmppc_get_pc(&vcpu_book3s->vcpu), eaddr, vcpu_book3s->sdr1, pteg,
sr_vsid(sre));
r = gfn_to_hva(vcpu->kvm, pteg >> PAGE_SHIFT);
if (kvm_is_error_hva(r))
return r;
return r | (pteg & ~PAGE_MASK);
}
static u32 kvmppc_mmu_book3s_32_get_ptem(u32 sre, gva_t eaddr, bool primary)
{
return ((eaddr & 0x0fffffff) >> 22) | (sr_vsid(sre) << 7) |
(primary ? 0 : 0x40) | 0x80000000;
}
static int kvmppc_mmu_book3s_32_xlate_bat(struct kvm_vcpu *vcpu, gva_t eaddr,
struct kvmppc_pte *pte, bool data,
bool iswrite)
{
struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
struct kvmppc_bat *bat;
int i;
for (i = 0; i < 8; i++) {
if (data)
bat = &vcpu_book3s->dbat[i];
else
bat = &vcpu_book3s->ibat[i];
if (vcpu->arch.shared->msr & MSR_PR) {
if (!bat->vp)
continue;
} else {
if (!bat->vs)
continue;
}
if (check_debug_ip(vcpu))
{
dprintk_pte("%cBAT %02d: 0x%lx - 0x%x (0x%x)\n",
data ? 'd' : 'i', i, eaddr, bat->bepi,
bat->bepi_mask);
}
if ((eaddr & bat->bepi_mask) == bat->bepi) {
u64 vsid;
kvmppc_mmu_book3s_32_esid_to_vsid(vcpu,
eaddr >> SID_SHIFT, &vsid);
vsid <<= 16;
pte->vpage = (((u64)eaddr >> 12) & 0xffff) | vsid;
pte->raddr = bat->brpn | (eaddr & ~bat->bepi_mask);
pte->may_read = bat->pp;
pte->may_write = bat->pp > 1;
pte->may_execute = true;
if (!pte->may_read) {
printk(KERN_INFO "BAT is not readable!\n");
continue;
}
if (iswrite && !pte->may_write) {
dprintk_pte("BAT is read-only!\n");
continue;
}
return 0;
}
}
return -ENOENT;
}
static int kvmppc_mmu_book3s_32_xlate_pte(struct kvm_vcpu *vcpu, gva_t eaddr,
struct kvmppc_pte *pte, bool data,
bool iswrite, bool primary)
{
u32 sre;
hva_t ptegp;
u32 pteg[16];
u32 ptem = 0;
int i;
int found = 0;
sre = find_sr(vcpu, eaddr);
dprintk_pte("SR 0x%lx: vsid=0x%x, raw=0x%x\n", eaddr >> 28,
sr_vsid(sre), sre);
pte->vpage = kvmppc_mmu_book3s_32_ea_to_vp(vcpu, eaddr, data);
ptegp = kvmppc_mmu_book3s_32_get_pteg(vcpu, sre, eaddr, primary);
if (kvm_is_error_hva(ptegp)) {
printk(KERN_INFO "KVM: Invalid PTEG!\n");
goto no_page_found;
}
ptem = kvmppc_mmu_book3s_32_get_ptem(sre, eaddr, primary);
if(copy_from_user(pteg, (void __user *)ptegp, sizeof(pteg))) {
printk(KERN_ERR "KVM: Can't copy data from 0x%lx!\n", ptegp);
goto no_page_found;
}
for (i=0; i<16; i+=2) {
if (ptem == pteg[i]) {
u8 pp;
pte->raddr = (pteg[i+1] & ~(0xFFFULL)) | (eaddr & 0xFFF);
pp = pteg[i+1] & 3;
if ((sr_kp(sre) && (vcpu->arch.shared->msr & MSR_PR)) ||
(sr_ks(sre) && !(vcpu->arch.shared->msr & MSR_PR)))
pp |= 4;
pte->may_write = false;
pte->may_read = false;
pte->may_execute = true;
switch (pp) {
case 0:
case 1:
case 2:
case 6:
pte->may_write = true;
case 3:
case 5:
case 7:
pte->may_read = true;
break;
}
dprintk_pte("MMU: Found PTE -> %x %x - %x\n",
pteg[i], pteg[i+1], pp);
found = 1;
break;
}
}
/* Update PTE C and A bits, so the guest's swapper knows we used the
page */
if (found) {
u32 pte_r = pteg[i+1];
char __user *addr = (char __user *) &pteg[i+1];
/*
* Use single-byte writes to update the HPTE, to
* conform to what real hardware does.
*/
if (pte->may_read && !(pte_r & PTEG_FLAG_ACCESSED)) {
pte_r |= PTEG_FLAG_ACCESSED;
put_user(pte_r >> 8, addr + 2);
}
if (iswrite && pte->may_write && !(pte_r & PTEG_FLAG_DIRTY)) {
pte_r |= PTEG_FLAG_DIRTY;
put_user(pte_r, addr + 3);
}
if (!pte->may_read || (iswrite && !pte->may_write))
return -EPERM;
return 0;
}
no_page_found:
if (check_debug_ip(vcpu)) {
dprintk_pte("KVM MMU: No PTE found (sdr1=0x%llx ptegp=0x%lx)\n",
to_book3s(vcpu)->sdr1, ptegp);
for (i=0; i<16; i+=2) {
dprintk_pte(" %02d: 0x%x - 0x%x (0x%x)\n",
i, pteg[i], pteg[i+1], ptem);
}
}
return -ENOENT;
}
static int kvmppc_mmu_book3s_32_xlate(struct kvm_vcpu *vcpu, gva_t eaddr,
struct kvmppc_pte *pte, bool data,
bool iswrite)
{
int r;
ulong mp_ea = vcpu->arch.magic_page_ea;
pte->eaddr = eaddr;
pte->page_size = MMU_PAGE_4K;
/* Magic page override */
if (unlikely(mp_ea) &&
unlikely((eaddr & ~0xfffULL) == (mp_ea & ~0xfffULL)) &&
!(vcpu->arch.shared->msr & MSR_PR)) {
pte->vpage = kvmppc_mmu_book3s_32_ea_to_vp(vcpu, eaddr, data);
pte->raddr = vcpu->arch.magic_page_pa | (pte->raddr & 0xfff);
pte->raddr &= KVM_PAM;
pte->may_execute = true;
pte->may_read = true;
pte->may_write = true;
return 0;
}
r = kvmppc_mmu_book3s_32_xlate_bat(vcpu, eaddr, pte, data, iswrite);
if (r < 0)
r = kvmppc_mmu_book3s_32_xlate_pte(vcpu, eaddr, pte,
data, iswrite, true);
if (r < 0)
r = kvmppc_mmu_book3s_32_xlate_pte(vcpu, eaddr, pte,
data, iswrite, false);
return r;
}
static u32 kvmppc_mmu_book3s_32_mfsrin(struct kvm_vcpu *vcpu, u32 srnum)
{
return vcpu->arch.shared->sr[srnum];
}
static void kvmppc_mmu_book3s_32_mtsrin(struct kvm_vcpu *vcpu, u32 srnum,
ulong value)
{
vcpu->arch.shared->sr[srnum] = value;
kvmppc_mmu_map_segment(vcpu, srnum << SID_SHIFT);
}
static void kvmppc_mmu_book3s_32_tlbie(struct kvm_vcpu *vcpu, ulong ea, bool large)
{
int i;
struct kvm_vcpu *v;
/* flush this VA on all cpus */
kvm_for_each_vcpu(i, v, vcpu->kvm)
kvmppc_mmu_pte_flush(v, ea, 0x0FFFF000);
}
static int kvmppc_mmu_book3s_32_esid_to_vsid(struct kvm_vcpu *vcpu, ulong esid,
u64 *vsid)
{
ulong ea = esid << SID_SHIFT;
u32 sr;
u64 gvsid = esid;
if (vcpu->arch.shared->msr & (MSR_DR|MSR_IR)) {
sr = find_sr(vcpu, ea);
if (sr_valid(sr))
gvsid = sr_vsid(sr);
}
/* In case we only have one of MSR_IR or MSR_DR set, let's put
that in the real-mode context (and hope RM doesn't access
high memory) */
switch (vcpu->arch.shared->msr & (MSR_DR|MSR_IR)) {
case 0:
*vsid = VSID_REAL | esid;
break;
case MSR_IR:
*vsid = VSID_REAL_IR | gvsid;
break;
case MSR_DR:
*vsid = VSID_REAL_DR | gvsid;
break;
case MSR_DR|MSR_IR:
if (sr_valid(sr))
*vsid = sr_vsid(sr);
else
*vsid = VSID_BAT | gvsid;
break;
default:
BUG();
}
if (vcpu->arch.shared->msr & MSR_PR)
*vsid |= VSID_PR;
return 0;
}
static bool kvmppc_mmu_book3s_32_is_dcbz32(struct kvm_vcpu *vcpu)
{
return true;
}
void kvmppc_mmu_book3s_32_init(struct kvm_vcpu *vcpu)
{
struct kvmppc_mmu *mmu = &vcpu->arch.mmu;
mmu->mtsrin = kvmppc_mmu_book3s_32_mtsrin;
mmu->mfsrin = kvmppc_mmu_book3s_32_mfsrin;
mmu->xlate = kvmppc_mmu_book3s_32_xlate;
mmu->reset_msr = kvmppc_mmu_book3s_32_reset_msr;
mmu->tlbie = kvmppc_mmu_book3s_32_tlbie;
mmu->esid_to_vsid = kvmppc_mmu_book3s_32_esid_to_vsid;
mmu->ea_to_vp = kvmppc_mmu_book3s_32_ea_to_vp;
mmu->is_dcbz32 = kvmppc_mmu_book3s_32_is_dcbz32;
mmu->slbmte = NULL;
mmu->slbmfee = NULL;
mmu->slbmfev = NULL;
mmu->slbie = NULL;
mmu->slbia = NULL;
}
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