From 20bccb82ff3ea09bcb7c4ee226d3160cab15f7da Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 24 Oct 2016 16:26:49 +0100 Subject: cpu: Support a target CPU having a variable page size Support target CPUs having a page size which isn't knownn at compile time. To use this, the CPU implementation should: * define TARGET_PAGE_BITS_VARY * not define TARGET_PAGE_BITS * define TARGET_PAGE_BITS_MIN to the smallest value it might possibly want for TARGET_PAGE_BITS * call set_preferred_target_page_bits() in its realize function to indicate the actual preferred target page size for the CPU (and report any error from it) In CONFIG_USER_ONLY, the CPU implementation should continue to define TARGET_PAGE_BITS appropriately for the guest OS page size. Machines which want to take advantage of having the page size something larger than TARGET_PAGE_BITS_MIN must set the MachineClass minimum_page_bits field to a value which they guarantee will be no greater than the preferred page size for any CPU they create. Note that changing the target page size by setting minimum_page_bits is a migration compatibility break for that machine. For debugging purposes, attempts to use TARGET_PAGE_SIZE before it has been finally confirmed will assert. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson --- include/exec/cpu-all.h | 9 +++++++++ include/hw/boards.h | 7 +++++++ include/qemu-common.h | 12 ++++++++++++ 3 files changed, 28 insertions(+) (limited to 'include') diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h index b6a705982f..861260d3db 100644 --- a/include/exec/cpu-all.h +++ b/include/exec/cpu-all.h @@ -189,6 +189,15 @@ void address_space_stq(AddressSpace *as, hwaddr addr, uint64_t val, /* page related stuff */ +#ifdef TARGET_PAGE_BITS_VARY +extern bool target_page_bits_decided; +extern int target_page_bits; +#define TARGET_PAGE_BITS ({ assert(target_page_bits_decided); \ + target_page_bits; }) +#else +#define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS +#endif + #define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS) #define TARGET_PAGE_MASK ~(TARGET_PAGE_SIZE - 1) #define TARGET_PAGE_ALIGN(addr) (((addr) + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK) diff --git a/include/hw/boards.h b/include/hw/boards.h index e46a744bcd..a51da9c440 100644 --- a/include/hw/boards.h +++ b/include/hw/boards.h @@ -86,6 +86,12 @@ typedef struct { * Returns a @HotpluggableCPUList, which describes CPUs objects which * could be added with -device/device_add. * Caller is responsible for freeing returned list. + * @minimum_page_bits: + * If non-zero, the board promises never to create a CPU with a page size + * smaller than this, so QEMU can use a more efficient larger page + * size than the target architecture's minimum. (Attempting to create + * such a CPU will fail.) Note that changing this is a migration + * compatibility break for the machine. */ struct MachineClass { /*< private >*/ @@ -124,6 +130,7 @@ struct MachineClass { ram_addr_t default_ram_size; bool option_rom_has_mr; bool rom_file_has_mr; + int minimum_page_bits; HotplugHandler *(*get_hotplug_handler)(MachineState *machine, DeviceState *dev); diff --git a/include/qemu-common.h b/include/qemu-common.h index 9e8b0bd991..7e6e4feb4b 100644 --- a/include/qemu-common.h +++ b/include/qemu-common.h @@ -81,6 +81,18 @@ bool tcg_enabled(void); void cpu_exec_init_all(void); +/** + * set_preferred_target_page_bits: + * @bits: number of bits needed to represent an address within the page + * + * Set the preferred target page size (the actual target page + * size may be smaller than any given CPU's preference). + * Returns true on success, false on failure (which can only happen + * if this is called after the system has already finalized its + * choice of page size and the requested page size is smaller than that). + */ +bool set_preferred_target_page_bits(int bits); + /** * Sends a (part of) iovec down a socket, yielding when the socket is full, or * Receives data into a (part of) iovec from a socket, -- cgit v1.2.3-55-g7522