Besides the LWN article Notes from the Intelpocalypse [1] this is the best high level overview I've seen for now. Here is are a few quotes (emphasis mine):
Am I affected by the bug?
Most certainly, yes.
Can I detect if someone has exploited Meltdown or Spectre against me?
Probably not. The exploitation does not leave any traces in traditional log files.
What can be leaked?
If your system is affected, our proof-of-concept exploit can read the memory content of your computer. This may include passwords and sensitive data stored on the system.
Which systems are affected by Meltdown?
Desktop, Laptop, and Cloud computers may be affected by Meltdown. More technically, every Intel processor which implements out-of-order execution is potentially affected, which is effectively every processor since 1995 (except Intel Itanium and Intel Atom before 2013). We successfully tested Meltdown on Intel processor generations released as early as 2011. Currently, we have only verified Meltdown on Intel processors. At the moment, it is unclear whether ARM and AMD processors are also affected by Meltdown.
Which systems are affected by Spectre?
Almost every system is affected by Spectre: Desktops, Laptops, Cloud Servers, as well as Smartphones. More specifically, all modern processors capable of keeping many instructions in flight are potentially vulnerable. In particular, we have verified Spectre on Intel, AMD, and ARM processors.
Which cloud providers are affected by Meltdown?
Cloud providers which use Intel CPUs and Xen PV as virtualization without having patches applied. Furthermore, cloud providers without real hardware virtualization, relying on containers that share one kernel, such as Docker, LXC, or OpenVZ are affected.
Why is it called Meltdown?
The bug basically melts security boundaries which are normally enforced by the hardware.
Why is it called Spectre?
The name is based on the root cause, speculative execution. As it is not easy to fix, it will haunt us for quite some time.
I don't see user-mode linux, QEMU, or KVM on that list, or am I mistaken an they are affected as well(so maybe some amd users are safe?). Another reason I advocate every spinup should have FDE by default with a ssh key entry shimmy at initram, or is this runtime cpu acccess so it gets anything live? If so that's scary.
Am I affected by the bug?
Most certainly, yes.
Can I detect if someone has exploited Meltdown or Spectre against me?
Probably not. The exploitation does not leave any traces in traditional log files.
What can be leaked?
If your system is affected, our proof-of-concept exploit can read the memory content of your computer. This may include passwords and sensitive data stored on the system.
Which systems are affected by Meltdown?
Desktop, Laptop, and Cloud computers may be affected by Meltdown. More technically, every Intel processor which implements out-of-order execution is potentially affected, which is effectively every processor since 1995 (except Intel Itanium and Intel Atom before 2013). We successfully tested Meltdown on Intel processor generations released as early as 2011. Currently, we have only verified Meltdown on Intel processors. At the moment, it is unclear whether ARM and AMD processors are also affected by Meltdown.
Which systems are affected by Spectre?
Almost every system is affected by Spectre: Desktops, Laptops, Cloud Servers, as well as Smartphones. More specifically, all modern processors capable of keeping many instructions in flight are potentially vulnerable. In particular, we have verified Spectre on Intel, AMD, and ARM processors.
Which cloud providers are affected by Meltdown?
Cloud providers which use Intel CPUs and Xen PV as virtualization without having patches applied. Furthermore, cloud providers without real hardware virtualization, relying on containers that share one kernel, such as Docker, LXC, or OpenVZ are affected.
Why is it called Meltdown?
The bug basically melts security boundaries which are normally enforced by the hardware.
Why is it called Spectre?
The name is based on the root cause, speculative execution. As it is not easy to fix, it will haunt us for quite some time.
[1] https://lwn.net/SubscriberLink/742702/e23889188fce9f7f/