Re: powerpc/64: Include KVM guest test in all interrupt vectors

[Michael Ellerman <mpe@ellerman.id.au>]

On Thu, 2015-12-11 at 05:44:42 UTC, Paul Mackerras wrote:
> Currently, if HV KVM is configured but PR KVM isn't, we don't include
> a test to see whether we were interrupted in KVM guest context for the
> set of interrupts which get delivered directly to the guest by hardware
> if they occur in the guest.  This includes things like program
> interrupts.
> 
> However, the recent bug where userspace could set the MSR for a VCPU
> to have an illegal value in the TS field, and thus cause a TM Bad Thing
> type of program interrupt on the hrfid that enters the guest, showed that
> we can never be completely sure that these interrupts can never occur
> in the guest entry/exit code.  If one of these interrupts does happen
> and we have HV KVM configured but not PR KVM, then we end up trying to
> run the handler in the host with the MMU set to the guest MMU context,
> which generally ends badly.
> 
> Thus, for robustness it is better to have the test in every interrupt
> vector, so that if some way is found to trigger some interrupt in the
> guest entry/exit path, we can handle it without immediately crashing
> the host.
> 
> This means that the distinction between KVMTEST and KVMTEST_PR goes
> away.  Thus we delete KVMTEST_PR and associated macros and use KVMTEST
> everywhere that we previously used either KVMTEST_PR or KVMTEST.  It
> also means that SOFTEN_TEST_HV_201 becomes the same as SOFTEN_TEST_PR,
> so we deleted SOFTEN_TEST_HV_201 and use SOFTEN_TEST_PR instead.
> 
> Signed-off-by: Paul Mackerras <paulus@samba.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/31a40e2b052c0f2b80df7b56

cheers