From e12f3a13e2e134fe9b8d3d1a160a8e54de1e8fa7 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Thu, 12 Jan 2017 19:24:15 +0100 Subject: fw-cfg: turn FW_CFG_FILE_SLOTS into a device property We'd like to raise the value of FW_CFG_FILE_SLOTS. Doing it naively could lead to problems with backward migration: a more recent QEMU (running an older machine type) would allow the guest, in fw_cfg_select(), to select a high key value that is unavailable in the same machine type implemented by the older (target) QEMU. On the target host, fw_cfg_data_read() for example could dereference nonexistent entries. As first step, size the FWCfgState.entries[*] and FWCfgState.entry_order arrays dynamically. All three array sizes will be influenced by the new field FWCfgState.file_slots (and matching device property). Make the following changes: - Replace the FW_CFG_FILE_SLOTS macro with FW_CFG_FILE_SLOTS_MIN (minimum count of fw_cfg file slots) in the header file. The value remains 0x10. - Replace all uses of FW_CFG_FILE_SLOTS with a helper function called fw_cfg_file_slots(), returning the new property. - Eliminate the macro FW_CFG_MAX_ENTRY, and replace all its uses with a helper function called fw_cfg_max_entry(). - In the MMIO- and IO-mapped realize functions both, allocate all three arrays dynamically, based on the new property. - The new property defaults to FW_CFG_FILE_SLOTS_MIN. This is going to be customized in the following patches. Cc: "Gabriel L. Somlo" Cc: "Michael S. Tsirkin" Cc: Gerd Hoffmann Cc: Igor Mammedov Cc: Paolo Bonzini Signed-off-by: Laszlo Ersek Acked-by: Gabriel Somlo Tested-by: Gabriel Somlo Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Eduardo Habkost --- docs/specs/fw_cfg.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'docs') diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt index a19e2adbe1..9373bbc647 100644 --- a/docs/specs/fw_cfg.txt +++ b/docs/specs/fw_cfg.txt @@ -156,7 +156,7 @@ Selector Reg. Range Usage 0xc000 - 0xffff Arch. Specific (0x0000 - 0x3fff, RW, ignored in v2.4+) In practice, the number of allowed firmware configuration items is given -by the value of FW_CFG_MAX_ENTRY (see fw_cfg.h). +by the value (FW_CFG_FILE_FIRST + FW_CFG_FILE_SLOTS_MIN) (see fw_cfg.h). = Guest-side DMA Interface = -- cgit v1.2.3