Liuw's Thinkpad

这屁事搞了好几天了，这里记一下。

三个入口：

1. do_mmu_update，个是最正规的ParaVirt入口，可以更新任何一级页表。
2. do_update_va_mapping，直接更新virtual address对应的L1页表，只能用于L1页表。
3. writable page table，实际上这是一个Xen的特性，不是一个具体的函数，也只能用于L1页表。Xen先把L1页表unhook让guest可写，然后ptwr_emulated_update为guest模拟写操作，Xen验证写入数据的合法性后再把页表重新hook上。

这是这几天看代码的一些小总结，不能保证完全正确。以后再写代码验证。

XenoLinux内核上面的方面都有采用。比如在Dom0进程要更新页表的时候（创建也好，销毁也好），通常是用do_mmu_update，效率比较高；但是在munmap单个页面的时候，通常是使用writable page table模式。

This is quite common when you add some non-official sources to ‘source.list’.

gpg --keyserver hkp://wwwkeys.eu.pgp.net --no-default-keyring --primary-keyring /etc/apt/trusted.gpg --recv KEYID

Choose key server as you wish. The critical part is that we specify apt’s keyring, rather than creating our own. If we miss those key ring options, gpg(1) will create a folder .gnupg in home directory, which comes out to be our personal settings, not apt(8)’s.

This is quite common when you add some non-official sources to ‘source.list’.

gpg --keyserver hkp://wwwkeys.eu.pgp.net --no-default-keyring --primary-keyring /etc/apt/trusted.gpg --recv KEYID

Choose key server as you wish. The critical part is that we specify apt’s keyring, rather than creating our own. If we miss those key ring options, gpg(1) will create a folder .gnupg in home directory, which comes out to be our personal settings, not apt(8)’s.