On 1/14/25 06:29, Tom Lendacky wrote: >> Given the choice between "a bug in the calling code >> crashes the kernel" and "a bug in the calling code >> results in a missed TLB flush", I'm guessing the >> crash is probably better. > So instead of the negative number protection, shouldn't this just use an > unsigned int for extra_count and panic() if the value is greater than > invlpgb_count_max? The caller has some sort of logic problem and it > could possibly result in missed TLB flushes. Or if a panic() is out of > the question, maybe a WARN() and a full TLB flush to be safe? The current implementation will panic in the #GP handler though. It should be pretty easy to figure out that INVLPGB is involved with RIP or the Code: snippet. From there, you'd need to figure out what caused the #GP. I guess the one nasty thing is that a person debugging this might not have a CPUID dump handy so wouldn't actually know the number of valid addresses that INVLPGB can take. But otherwise, I'm not sure an explicit panic adds _much_ value here over an implicit one via the #GP handler. I don't know how everybody else feels about it, but I'm happy just depending on the #GP for now.
