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[RFC PATCH v2 0/3] hw/block/pflash: Mmap read-only backend files with MA
From: |
Philippe Mathieu-Daudé |
Subject: |
[RFC PATCH v2 0/3] hw/block/pflash: Mmap read-only backend files with MAP_SHARED |
Date: |
Mon, 1 Mar 2021 12:53:26 +0100 |
Since v1:
- check driver is "raw" (David)
- ignore CFI02 for now
Hi,
This series aims to reduce the memory footprint of flash devices
when the backing file is read-only.
When a backing file is read-only, the model considers the flash
is in "protected" mode. No write are allowed, but the MMIO
state machine is still usable.
This series introduces a new memory region helper to mmap files
and use it with the pflash device (only with read-only backing
files).
The goal is to reduce QEMU's memory footprint when multiple VMs
are instantiated using the same read-only backing file, which is
the case with the CODE flash from OVMF and AAVMF.
Previous attempts:
- Huawei
https://www.mail-archive.com/qemu-devel@nongnu.org/msg607292.html
- Tencent
https://www.mail-archive.com/qemu-devel@nongnu.org/msg742066.html
- Oracle
https://www.mail-archive.com/qemu-devel@nongnu.org/msg760065.html
RFC because yet another approach to tackle this technical debt,
and very little tested.
Regards,
Phil.
Philippe Mathieu-Daudé (3):
exec/memory: Introduce memory_region_init_rom_device_from_file()
hw/block/pflash: Move code around
hw/block/pflash: use memory_region_init_rom_device_from_file()
include/exec/memory.h | 85 +++++++++++++++++++++++++++++++++++
hw/block/pflash_cfi01.c | 49 +++++++++++++++------
hw/block/pflash_cfi02.c | 18 ++++----
softmmu/memory.c | 98 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 228 insertions(+), 22 deletions(-)
--
2.26.2
- [RFC PATCH v2 0/3] hw/block/pflash: Mmap read-only backend files with MAP_SHARED,
Philippe Mathieu-Daudé <=