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i386: load kernel on xen using DMA

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Kernel on Xen is loaded via fw_cfg. Previously it used non-DMA version,
which loaded the kernel (and initramfs) byte by byte. Change this
to DMA, to load in bigger chunks.
This change alone reduces load time of a (big) kernel+initramfs from
~10s down to below 1s.

This change was suggested initially here:
https://lore.kernel.org/xen-devel/20180216204031.000052e9@gmail.com/
Apparently this alone is already enough to get massive speedup.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20210426034709.595432-1-marmarek@invisiblethingslab.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Marek Marczykowski-Górecki 2021-04-26 05:47:10 +02:00 committed by Anthony PERARD
parent 9253d83062
commit 918a7f706b
1 changed files with 2 additions and 1 deletions
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3
hw/i386/pc.c
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@ -718,7 +718,8 @@ void xen_load_linux(PCMachineState *pcms)
assert(MACHINE(pcms)->kernel_filename != NULL);
fw_cfg = fw_cfg_init_io(FW_CFG_IO_BASE);
fw_cfg = fw_cfg_init_io_dma(FW_CFG_IO_BASE, FW_CFG_IO_BASE + 4,
&address_space_memory);
fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, x86ms->boot_cpus);
rom_set_fw(fw_cfg);