Richard Henderson <richard.hender...@linaro.org> writes:
> It does not require going through the whole I/O path
> in order to discard a write.
>
> Reviewed-by: David Hildenbrand <da...@redhat.com>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> include/exec/cpu-all.h | 5 ++++-
> include/exec/cpu-common.h | 1 -
> accel/tcg/cputlb.c | 35 +++++++++++++++++++--------------
> exec.c | 41 +--------------------------------------
> 4 files changed, 25 insertions(+), 57 deletions(-)
>
> diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
> index d148bded35..26547cd6dd 100644
> --- a/include/exec/cpu-all.h
> +++ b/include/exec/cpu-all.h
<snip>
> @@ -822,16 +821,17 @@ void tlb_set_page_with_attrs(CPUState *cpu,
> target_ulong vaddr,
>
> tn.addr_write = -1;
> if (prot & PAGE_WRITE) {
> - if ((memory_region_is_ram(section->mr) && section->readonly)
> - || memory_region_is_romd(section->mr)) {
> - /* Write access calls the I/O callback. */
> - tn.addr_write = address | TLB_MMIO;
> - } else if (memory_region_is_ram(section->mr)
> - && cpu_physical_memory_is_clean(
> - memory_region_get_ram_addr(section->mr) + xlat)) {
> - tn.addr_write = address | TLB_NOTDIRTY;
> - } else {
> - tn.addr_write = address;
> + tn.addr_write = address;
> + if (memory_region_is_romd(section->mr)) {
> + /* Use the MMIO path so that the device can switch states. */
> + tn.addr_write |= TLB_MMIO;
> + } else if (memory_region_is_ram(section->mr)) {
> + if (section->readonly) {
> + tn.addr_write |= TLB_ROM;
> + } else if (cpu_physical_memory_is_clean(
> + memory_region_get_ram_addr(section->mr) + xlat)) {
> + tn.addr_write |= TLB_NOTDIRTY;
> + }
This reads a bit weird because we are saying romd isn't a ROM but
something that identifies as RAM can be ROM rather than just a memory
protected piece of RAM.
> }
> if (prot & PAGE_WRITE_INV) {
> tn.addr_write |= TLB_INVALID_MASK;
So at the moment I don't see what the TLB_ROM flag gives us that setting
TLB_INVALID doesn't - either way we won't make the write to our
ram-not-ram-rom.
> @@ -904,7 +904,7 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry
> *iotlbentry,
> mr = section->mr;
> mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
> cpu->mem_io_pc = retaddr;
> - if (mr != &io_mem_rom && mr != &io_mem_notdirty && !cpu->can_do_io) {
> + if (mr != &io_mem_notdirty && !cpu->can_do_io) {
> cpu_io_recompile(cpu, retaddr);
> }
>
> @@ -945,7 +945,7 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry
> *iotlbentry,
> section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
> mr = section->mr;
> mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
> - if (mr != &io_mem_rom && mr != &io_mem_notdirty && !cpu->can_do_io) {
> + if (mr != &io_mem_notdirty && !cpu->can_do_io) {
> cpu_io_recompile(cpu, retaddr);
> }
> cpu->mem_io_vaddr = addr;
> @@ -1125,7 +1125,7 @@ void *probe_access(CPUArchState *env, target_ulong
> addr, int size,
> }
>
> /* Reject I/O access, or other required slow-path. */
> - if (tlb_addr & (TLB_NOTDIRTY | TLB_MMIO | TLB_BSWAP)) {
> + if (tlb_addr & (TLB_NOTDIRTY | TLB_MMIO | TLB_BSWAP | TLB_ROM)) {
> return NULL;
> }
>
> @@ -1613,6 +1613,11 @@ store_helper(CPUArchState *env, target_ulong addr,
> uint64_t val,
> return;
> }
>
> + /* Ignore writes to ROM. */
> + if (unlikely(tlb_addr & TLB_ROM)) {
> + return;
> + }
> +
> haddr = (void *)((uintptr_t)addr + entry->addend);
>
> if (unlikely(need_swap)) {
> diff --git a/exec.c b/exec.c
> index 5f2587b621..ea8c0b18ac 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -88,7 +88,7 @@ static MemoryRegion *system_io;
> AddressSpace address_space_io;
> AddressSpace address_space_memory;
>
> -MemoryRegion io_mem_rom, io_mem_notdirty;
> +MemoryRegion io_mem_notdirty;
> static MemoryRegion io_mem_unassigned;
> #endif
>
> @@ -192,7 +192,6 @@ typedef struct subpage_t {
>
> #define PHYS_SECTION_UNASSIGNED 0
> #define PHYS_SECTION_NOTDIRTY 1
> -#define PHYS_SECTION_ROM 2
>
> static void io_mem_init(void);
> static void memory_map_init(void);
> @@ -1475,8 +1474,6 @@ hwaddr memory_region_section_get_iotlb(CPUState *cpu,
> iotlb = memory_region_get_ram_addr(section->mr) + xlat;
> if (!section->readonly) {
> iotlb |= PHYS_SECTION_NOTDIRTY;
> - } else {
> - iotlb |= PHYS_SECTION_ROM;
> }
> } else {
> AddressSpaceDispatch *d;
> @@ -3002,38 +2999,6 @@ static uint16_t dummy_section(PhysPageMap *map,
> FlatView *fv, MemoryRegion *mr)
> return phys_section_add(map, §ion);
> }
>
> -static void readonly_mem_write(void *opaque, hwaddr addr,
> - uint64_t val, unsigned size)
> -{
> - /* Ignore any write to ROM. */
> -}
> -
> -static bool readonly_mem_accepts(void *opaque, hwaddr addr,
> - unsigned size, bool is_write,
> - MemTxAttrs attrs)
> -{
> - return is_write;
> -}
> -
> -/* This will only be used for writes, because reads are special cased
> - * to directly access the underlying host ram.
> - */
> -static const MemoryRegionOps readonly_mem_ops = {
> - .write = readonly_mem_write,
> - .valid.accepts = readonly_mem_accepts,
> - .endianness = DEVICE_NATIVE_ENDIAN,
> - .valid = {
> - .min_access_size = 1,
> - .max_access_size = 8,
> - .unaligned = false,
> - },
> - .impl = {
> - .min_access_size = 1,
> - .max_access_size = 8,
> - .unaligned = false,
> - },
> -};
> -
> MemoryRegionSection *iotlb_to_section(CPUState *cpu,
> hwaddr index, MemTxAttrs attrs)
> {
> @@ -3047,8 +3012,6 @@ MemoryRegionSection *iotlb_to_section(CPUState *cpu,
>
> static void io_mem_init(void)
> {
> - memory_region_init_io(&io_mem_rom, NULL, &readonly_mem_ops,
> - NULL, NULL, UINT64_MAX);
> memory_region_init_io(&io_mem_unassigned, NULL, &unassigned_mem_ops,
> NULL,
> NULL, UINT64_MAX);
>
> @@ -3069,8 +3032,6 @@ AddressSpaceDispatch
> *address_space_dispatch_new(FlatView *fv)
> assert(n == PHYS_SECTION_UNASSIGNED);
> n = dummy_section(&d->map, fv, &io_mem_notdirty);
> assert(n == PHYS_SECTION_NOTDIRTY);
> - n = dummy_section(&d->map, fv, &io_mem_rom);
> - assert(n == PHYS_SECTION_ROM);
>
> d->phys_map = (PhysPageEntry) { .ptr = PHYS_MAP_NODE_NIL, .skip = 1 };
--
Alex Bennée
