I'm also curious whether they're vulnerable to spectre (any variant)
I seriously doubt it—that was nearly 3 years ago.
According to an Ars Technica article, ARM dealt with the issue far better than Intel or AMD [1]:
"ARM's response was the gold standard. Lots of technical detail in a whitepaper, but ARM chose to let that stand alone, without the misleading PR of Intel or the vague imprecision of AMD.
For the array bounds attack, ARM is introducing a new instruction that provides a speculation barrier; similar to Intel's serializing instructions, the new ARM instruction should be inserted between the test of array bounds and the array access itself. ARM even provides sample code to show this."
I seriously doubt it—that was nearly 3 years ago.
According to an Ars Technica article, ARM dealt with the issue far better than Intel or AMD [1]:
"ARM's response was the gold standard. Lots of technical detail in a whitepaper, but ARM chose to let that stand alone, without the misleading PR of Intel or the vague imprecision of AMD. For the array bounds attack, ARM is introducing a new instruction that provides a speculation barrier; similar to Intel's serializing instructions, the new ARM instruction should be inserted between the test of array bounds and the array access itself. ARM even provides sample code to show this."
[1]: https://arstechnica.com/gadgets/2018/01/meltdown-and-spectre...