On Mon, Jan 17, 2022 at 06:45:36PM +0100, Paolo Bonzini wrote: > On 1/14/22 16:19, Mark Rutland wrote: > > I also think there is another issue here. When an IRQ is taken from SIE, will > > user_mode(regs) always be false, or could it be true if the guest userspace is > > running? If it can be true I think tha context tracking checks can complain, > > and it*might* be possible to trigger a panic(). > > I think that it would be false, because the guest PSW is in the SIE block > and switched on SIE entry and exit, but I might be incorrect. Ah; that's the crux of my confusion: I had thought the guest PSW would be placed in the regular lowcore *_old_psw slots. From looking at the entry asm it looks like the host PSW (around the invocation of SIE) is stored there, since that's what the OUTSIDE + SIEEXIT handling is checking for. Assuming that's correct, I agree this problem doesn't exist, and there's only the common RCU/tracing/lockdep management to fix. Sorry for the noise, and thanks for the pointer! Thanks, Mark.
