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vmm: Mark guest persistent memory pages as mergeable

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In case the VM is started with the flag "--pmem mergeable=on", it means
the user expects the guest persistent memory pages to be marked as
mergeable. This commit relies on the madvise(MADV_MERGEABLE) system call
to inform the host kernel about these pages.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf 2019-11-19 15:22:20 -08:00 committed by Rob Bradford
parent 0f9afc3017
commit f979380620
1 changed files with 25 additions and 0 deletions
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25
vmm/src/device_manager.rs
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@ -1078,6 +1078,31 @@ impl DeviceManager {
// Safe because the guest regions are guaranteed not to overlap.
let _ = unsafe { vm_info.vm_fd.set_user_memory_region(mem_region) };
// Mark the pages as mergeable if explicitly asked for.
if pmem_cfg.mergeable {
// Safe because the address and size are valid since the
// mmap succeeded..
let ret = unsafe {
libc::madvise(
addr as *mut libc::c_void,
size as libc::size_t,
libc::MADV_MERGEABLE,
)
};
if ret != 0 {
let err = io::Error::last_os_error();
// Safe to unwrap because the error is constructed with
// last_os_error(), which ensures the output will be Some().
let errno = err.raw_os_error().unwrap();
if errno == libc::EINVAL {
warn!("kernel not configured with CONFIG_KSM");
} else {
warn!("madvise error: {}", err);
}
warn!("failed to mark pages as mergeable");
}
}
// Increment the KVM slot number
*mem_slots += 1;