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tcg: Support MMU protection regions smaller than TARGET_PAGE_SIZE

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Add support for MMU protection regions that are smaller than
TARGET_PAGE_SIZE. We do this by marking the TLB entry for those
pages with a flag TLB_RECHECK. This flag causes us to always
take the slow-path for accesses. In the slow path we can then
special case them to always call tlb_fill() again, so we have
the correct information for the exact address being accessed.

This change allows us to handle reading and writing from small
regions; we cannot deal with execution from the small region.

Backports commit 55df6fcf5476b44bc1b95554e686ab3e91d725c5 from qemu
This commit is contained in:
Peter Maydell 2018-11-16 21:34:05 -05:00 committed by Lioncash
parent 3a0ab1a64a
commit 1301becdab
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
3 changed files with 127 additions and 28 deletions
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126
qemu/accel/tcg/cputlb.c
View file

@ -192,26 +192,40 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
target_ulong code_address;
uintptr_t addend;
CPUTLBEntry *te;
hwaddr iotlb, xlat, sz;
hwaddr iotlb, xlat, sz, paddr_page;
target_ulong vaddr_page;
unsigned vidx = env->vtlb_index++ % CPU_VTLB_SIZE;
int asidx = cpu_asidx_from_attrs(cpu, attrs);
assert(size >= TARGET_PAGE_SIZE);
if (size != TARGET_PAGE_SIZE) {
tlb_add_large_page(env, vaddr, size);
if (size < TARGET_PAGE_SIZE) {
sz = TARGET_PAGE_SIZE;
} else {
if (size > TARGET_PAGE_SIZE) {
tlb_add_large_page(env, vaddr, size);
}
sz = size;
}
vaddr_page = vaddr & TARGET_PAGE_MASK;
paddr_page = paddr & TARGET_PAGE_MASK;
sz = size;
section = address_space_translate_for_iotlb(cpu, asidx, paddr, &xlat, &sz,
attrs, &prot);
section = address_space_translate_for_iotlb(cpu, asidx, paddr_page,
&xlat, &sz, attrs, &prot);
assert(sz >= TARGET_PAGE_SIZE);
tlb_debug("vaddr=" TARGET_FMT_lx " paddr=0x" TARGET_FMT_plx
" prot=%x idx=%d\n",
vaddr, paddr, prot, mmu_idx);
address = vaddr;
if (!memory_region_is_ram(section->mr) && !memory_region_is_romd(section->mr)) {
address = vaddr_page;
if (size < TARGET_PAGE_SIZE) {
/*
* Slow-path the TLB entries; we will repeat the MMU check and TLB
* fill on every access.
*/
address |= TLB_RECHECK;
}
if (!memory_region_is_ram(section->mr) &&
!memory_region_is_romd(section->mr)) {
/* IO memory case */
address |= TLB_MMIO;
addend = 0;
@ -221,10 +235,10 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
}
code_address = address;
iotlb = memory_region_section_get_iotlb(cpu, section, vaddr, paddr, xlat,
prot, &address);
iotlb = memory_region_section_get_iotlb(cpu, section, vaddr_page,
paddr_page, xlat, prot, &address);
index = (vaddr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
index = (vaddr_page >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
te = &env->tlb_table[mmu_idx][index];
/* do not discard the translation in te, evict it into a victim tlb */
@ -237,16 +251,16 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
* TARGET_PAGE_BITS, and either
* + the ram_addr_t of the page base of the target RAM (if NOTDIRTY or ROM)
* + the offset within section->mr of the page base (otherwise)
* We subtract the vaddr (which is page aligned and thus won't
* We subtract the vaddr_page (which is page aligned and thus won't
* disturb the low bits) to give an offset which can be added to the
* (non-page-aligned) vaddr of the eventual memory access to get
* the MemoryRegion offset for the access. Note that the vaddr we
* subtract here is that of the page base, and not the same as the
* vaddr we add back in io_readx()/io_writex()/get_page_addr_code().
*/
env->iotlb[mmu_idx][index].addr = iotlb - vaddr;
env->iotlb[mmu_idx][index].addr = iotlb - vaddr_page;
env->iotlb[mmu_idx][index].attrs = attrs;
te->addend = (uintptr_t)(addend - vaddr);
te->addend = addend - vaddr_page;
if (prot & PAGE_READ) {
te->addr_read = address;
} else {
@ -322,6 +336,32 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env, target_ulong addr)
return RAM_ADDR_INVALID;
}
}
if (unlikely(env->tlb_table[mmu_idx][index].addr_code & TLB_RECHECK)) {
/*
* This is a TLB_RECHECK access, where the MMU protection
* covers a smaller range than a target page, and we must
* repeat the MMU check here. This tlb_fill() call might
* longjump out if this access should cause a guest exception.
*/
int index;
target_ulong tlb_addr;
tlb_fill(cpu, addr, 0, MMU_INST_FETCH, mmu_idx, 0);
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
tlb_addr = env->tlb_table[mmu_idx][index].addr_code;
if (!(tlb_addr & ~(TARGET_PAGE_MASK | TLB_RECHECK))) {
/* RAM access. We can't handle this, so for now just stop */
cpu_abort(cpu, "Unable to handle guest executing from RAM within "
"a small MPU region at 0x" TARGET_FMT_lx, addr);
}
/*
* Fall through to handle IO accesses (which will almost certainly
* also result in failure)
*/
}
iotlbentry = &env->iotlb[mmu_idx][index];
section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
mr = section->mr;
@ -466,7 +506,8 @@ void tlb_flush_page_by_mmuidx(CPUState *cpu, target_ulong addr, uint16_t idxmap)
static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
int mmu_idx,
target_ulong addr, uintptr_t retaddr, int size)
target_ulong addr, uintptr_t retaddr,
bool recheck, int size)
{
CPUState *cpu = ENV_GET_CPU(env);
hwaddr mr_offset;
@ -475,6 +516,29 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
uint64_t val;
MemTxResult r;
if (recheck) {
/*
* This is a TLB_RECHECK access, where the MMU protection
* covers a smaller range than a target page, and we must
* repeat the MMU check here. This tlb_fill() call might
* longjump out if this access should cause a guest exception.
*/
int index;
target_ulong tlb_addr;
tlb_fill(cpu, addr, size, MMU_DATA_LOAD, mmu_idx, retaddr);
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
tlb_addr = env->tlb_table[mmu_idx][index].addr_read;
if (!(tlb_addr & ~(TARGET_PAGE_MASK | TLB_RECHECK))) {
/* RAM access */
uintptr_t haddr = addr + env->tlb_table[mmu_idx][index].addend;
return ldn_p((void *)haddr, size);
}
/* Fall through for handling IO accesses */
}
section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
mr = section->mr;
mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
@ -500,7 +564,7 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
int mmu_idx,
uint64_t val, target_ulong addr,
uintptr_t retaddr, int size)
uintptr_t retaddr, bool recheck, int size)
{
CPUState *cpu = ENV_GET_CPU(env);
hwaddr mr_offset;
@ -508,6 +572,30 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
MemoryRegion *mr;
MemTxResult r;
if (recheck) {
/*
* This is a TLB_RECHECK access, where the MMU protection
* covers a smaller range than a target page, and we must
* repeat the MMU check here. This tlb_fill() call might
* longjump out if this access should cause a guest exception.
*/
int index;
target_ulong tlb_addr;
tlb_fill(cpu, addr, size, MMU_DATA_STORE, mmu_idx, retaddr);
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
if (!(tlb_addr & ~(TARGET_PAGE_MASK | TLB_RECHECK))) {
/* RAM access */
uintptr_t haddr = addr + env->tlb_table[mmu_idx][index].addend;
stn_p((void *)haddr, size, val);
return;
}
/* Fall through for handling IO accesses */
}
section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
mr = section->mr;
mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
@ -633,8 +721,8 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
tlb_addr = tlb_addr & ~TLB_NOTDIRTY;
}
/* Notice an IO access */
if (unlikely(tlb_addr & ~TARGET_PAGE_MASK)) {
/* Notice an IO access or a needs-MMU-lookup access */
if (unlikely(tlb_addr & (TLB_MMIO | TLB_RECHECK))) {
/* There's really nothing that can be done to
support this apart from stop-the-world. */
goto stop_the_world;

24
qemu/accel/tcg/softmmu_template.h
View file

@ -100,10 +100,12 @@
static inline DATA_TYPE glue(io_read, SUFFIX)(CPUArchState *env,
size_t mmu_idx, size_t index,
target_ulong addr,
uintptr_t retaddr)
uintptr_t retaddr,
bool recheck)
{
CPUIOTLBEntry *iotlbentry = &env->iotlb[mmu_idx][index];
return io_readx(env, iotlbentry, mmu_idx, addr, retaddr, DATA_SIZE);
return io_readx(env, iotlbentry, mmu_idx, addr, retaddr, recheck,
DATA_SIZE);
}
#endif
@ -247,7 +249,8 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, target_ulong addr,
/* ??? Note that the io helpers always read data in the target
byte ordering. We should push the LE/BE request down into io. */
res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr);
res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr,
tlb_addr & TLB_RECHECK);
res = TGT_LE(res);
goto _out;
}
@ -431,7 +434,8 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, target_ulong addr,
/* ??? Note that the io helpers always read data in the target
byte ordering. We should push the LE/BE request down into io. */
res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr);
res = glue(io_read, SUFFIX)(env, mmu_idx, index, addr, retaddr,
tlb_addr & TLB_RECHECK);
res = TGT_BE(res);
goto _out;
}
@ -496,10 +500,12 @@ static inline void glue(io_write, SUFFIX)(CPUArchState *env,
size_t mmu_idx, size_t index,
DATA_TYPE val,
target_ulong addr,
uintptr_t retaddr)
uintptr_t retaddr,
bool recheck)
{
CPUIOTLBEntry *iotlbentry = &env->iotlb[mmu_idx][index];
return io_writex(env, iotlbentry, mmu_idx, val, addr, retaddr, DATA_SIZE);
return io_writex(env, iotlbentry, mmu_idx, val, addr, retaddr,
recheck, DATA_SIZE);
}
void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
@ -601,7 +607,8 @@ void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
/* ??? Note that the io helpers always read data in the target
byte ordering. We should push the LE/BE request down into io. */
val = TGT_LE(val);
glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr);
glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr,
retaddr, tlb_addr & TLB_RECHECK);
return;
}
@ -746,7 +753,8 @@ void helper_be_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
/* ??? Note that the io helpers always read data in the target
byte ordering. We should push the LE/BE request down into io. */
val = TGT_BE(val);
glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr);
glue(io_write, SUFFIX)(env, mmu_idx, index, val, addr, retaddr,
tlb_addr & TLB_RECHECK);
return;
}

5
qemu/include/exec/cpu-all.h
View file

@ -363,11 +363,14 @@ CPUArchState *cpu_copy(CPUArchState *env);
#define TLB_NOTDIRTY (1 << (TARGET_PAGE_BITS - 2))
/* Set if TLB entry is an IO callback. */
#define TLB_MMIO (1 << (TARGET_PAGE_BITS - 3))
/* Set if TLB entry must have MMU lookup repeated for every access */
#define TLB_RECHECK (1 << (TARGET_PAGE_BITS - 4))
/* Use this mask to check interception with an alignment mask
* in a TCG backend.
*/
#define TLB_FLAGS_MASK (TLB_INVALID_MASK | TLB_NOTDIRTY | TLB_MMIO)
#define TLB_FLAGS_MASK (TLB_INVALID_MASK | TLB_NOTDIRTY | TLB_MMIO \
| TLB_RECHECK)
/**
* tlb_hit_page: return true if page aligned @addr is a hit against the