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vmm: Mark guest RAM pages as mergeable

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In case the VM is started with the flag "--memory mergeable=on", it
means the user expects the guest RAM 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 13:31:54 -08:00 committed by Rob Bradford
parent 880f62bab8
commit e4e8062dda
1 changed files with 29 additions and 2 deletions
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31
vmm/src/vm.rs
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@ -301,9 +301,36 @@ impl Vm {
};
// Safe because the guest regions are guaranteed not to overlap.
unsafe { fd.set_user_memory_region(mem_region) }
unsafe { fd.set_user_memory_region(mem_region) }?;
// Mark the pages as mergeable if explicitly asked for.
if config.memory.mergeable {
// Safe because the address and size are valid since the
// mmap succeeded.
let ret = unsafe {
libc::madvise(
region.as_ptr() as *mut libc::c_void,
region.len() 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");
}
}
Ok(())
})
.map_err(|_| Error::GuestMemory(MmapError::NoMemoryRegion))?;
.map_err(|_: io::Error| Error::GuestMemory(MmapError::NoMemoryRegion))?;
// Set TSS
fd.set_tss_address(arch::x86_64::layout::KVM_TSS_ADDRESS.raw_value() as usize)