Re: [RFC v2 08/32] x86/traps: Add #VE support for TDX guest

[Dave Hansen]

On 5/13/21 12:47 PM, Andi Kleen wrote:
> I don't see what could be added. If you have concrete suggestions please
> just propose something.

Oh, boy, I love writing changelogs!  I was hoping that the TDX folks
would chip in to write their own changelogs, but oh well.  You made my day!

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Virtualization Exceptions (#VE) are delivered to TDX guests due to
specific guest actions which may happen in either userspace or the kernel:

 * Specific instructions (WBINVD, for example)
 * Specific MSR accesses
 * Specific CPUID leaf accesses
 * Access to TD-shared memory, which includes MMIO

#VE exceptions are never generated on accesses to normal, TD-private memory.

The entry paths do not access TD-shared memory or use those specific
MSRs, instructions, CPUID leaves.  In addition, all interrupts including
NMIs are blocked by the hardware starting with #VE delivery until
TDGETVEINFO is called.  This eliminates the chance of a #VE during the
syscall gap or paranoid entry paths and simplifies #VE handling.

If a guest kernel action which would normally cause a #VE occurs in the
interrupt-disabled region before TDGETVEINFO, a #DF is delivered to the
guest.

Add basic infrastructure to handle any #VE which occurs in the kernel or
userspace.  Later patches will add handling for specific #VE scenarios.

Convert unhandled #VE's (everything, until later in this series) so that
they appear just like a #GP by calling do_general_protection() directly.

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Did I miss anything?