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Re: [PATCH V3 07/22] cpr
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From: |
Steven Sistare |
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Subject: |
Re: [PATCH V3 07/22] cpr |
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Date: |
Thu, 13 May 2021 16:21:02 -0400 |
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User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 |
On 5/12/2021 12:19 PM, Stefan Hajnoczi wrote:
> On Fri, May 07, 2021 at 05:25:05AM -0700, Steve Sistare wrote:
>> To use the restart mode, qemu must be started with the memfd-alloc machine
>> option. The memfd's are saved to the environment and kept open across exec,
>> after which they are found from the environment and re-mmap'd. Hence guest
>> ram is preserved in place, albeit with new virtual addresses in the qemu
>> process. The caller resumes the guest by calling cprload, which loads
>> state from the file. If the VM was running at cprsave time, then VM
>> execution resumes. cprsave supports any type of guest image and block
>> device, but the caller must not modify guest block devices between cprsave
>> and cprload.
>
> Does QEMU's existing -object memory-backend-file on tmpfs or hugetlbfs
> achieve the same thing?
Not quite. Various secondary anonymous memory objects are allocated via
ram_block_add
and must be preserved, such as these on x86_64.
vga.vram
pc.ram
pc.bios
pc.rom
vga.rom
rom@etc/acpi/tables
rom@etc/table-loader
rom@etc/acpi/rsdp
Even the read-only areas must be preserved rather than recreated from files in
the updated
qemu, as their contents may have changed.
- Steve
- Re: [PATCH V3 06/22] vl: add helper to request re-exec, (continued)
Re: [PATCH V3 06/22] vl: add helper to request re-exec, Stefan Hajnoczi, 2021/05/12
[PATCH V3 03/22] oslib: qemu_clr_cloexec, Steve Sistare, 2021/05/07
[PATCH V3 05/22] machine: memfd-alloc option, Steve Sistare, 2021/05/07
[PATCH V3 01/22] as_flat_walk, Steve Sistare, 2021/05/07
[PATCH V3 02/22] qemu_ram_volatile, Steve Sistare, 2021/05/07
[PATCH V3 07/22] cpr, Steve Sistare, 2021/05/07
[PATCH V3 11/22] vfio-pci: refactor for cpr, Steve Sistare, 2021/05/07
[PATCH V3 14/22] vhost: reset vhost devices upon cprsave, Steve Sistare, 2021/05/07
[PATCH V3 10/22] pci: export functions for cpr, Steve Sistare, 2021/05/07