Hi Borislav, Punit, On 01/03/18 22:35, Borislav Petkov wrote: > On Thu, Mar 01, 2018 at 06:06:59PM +0000, Punit Agrawal wrote: >> The 64-bit support lives in arch/arm64 and the die() there doesn't >> contain an oops_begin()/oops_end(). But the lack of oops_begin() on >> arm64 doesn't really matter here. >> One issue I see with calling die() is that it is defined in different >> includes across various architectures, (e.g., include/asm/kdebug.h for >> x86, include/asm/system_misc.h in arm64, etc.) > > I don't think that's insurmountable. I don't think die() helps us, its not quite the same as oops_begin()/panic(), which means we're interpreting the APEI notification's severity differently, depending on when we took it. > The more important question is, can we do the same set of calls when > panic severity on all architectures which support APEI or should we have > arch-specific ghes_panic() callbacks or so. I think the purpose of this oops_begin() is to ensure two CPUs calling oops_begin() at the same time don't have their traces interleaved, unblanks the screen and 'busts' any spinlocks printk() may need (console etc). This code is called in_nmi(), printk() now supports this so it doesn't need its locks busting. When called in_nmi(), printk batches the messages into its per-cpu printk_safe_seq_buf, which in our case is dumped by panic() using printk_safe_flush_on_panic(). So provided we call panic(), the in_nmi() messages from ghes.c are already batched, and printed behind panic()'s atomic_cmpxchg() exclusion thing. If your arm64 system has one of these futuristic 'screens', they get unblanked when panic() calls console_verbose() and bust_spinlocks(1). > As it is now, it would turn into a mess if we start with the ifdeffery > and the different requirements architectures might have... Today its just x86 and arm64. arm64 doesn't have a hook to do this. I'm happy to add an empty declaration or leave it under an ifdef until someone complains about any behaviour I missed! Thanks, James -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
