powerpc/64s/exception: Move KVM test to common code

This allows more code to be moved out of unrelocated regions. The
system call KVMTEST is changed to be open-coded and remain in the
tramp area to avoid having to move it to entry_64.S. The custom nature
of the system call entry code means the hcall case can be made more
streamlined than regular interrupt handlers.

mpe: Incorporate fix from Nick:

Moving KVM test to the common entry code missed the case of HMI and
MCE, which do not do __GEN_COMMON_ENTRY (because they don't want to
switch to virt mode).

This means a MCE or HMI exception that is taken while KVM is running a
guest context will not be switched out of that context, and KVM won't
be notified. Found by running sigfuz in guest with patched host on
POWER9 DD2.3, which causes some TM related HMI interrupts (which are
expected and supposed to be handled by KVM).

This fix adds a __GEN_REALMODE_COMMON_ENTRY for those handlers to add
the KVM test. This makes them look a little more like other handlers
that all use __GEN_COMMON_ENTRY.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-13-npiggin@gmail.com

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -1266,7 +1266,6 @@ kvmppc_interrupt_hv:
 	 * R12		= (guest CR << 32) | interrupt vector
 	 * R13		= PACA
 	 * guest R12 saved in shadow VCPU SCRATCH0
-	 * guest CTR saved in shadow VCPU SCRATCH1 if RELOCATABLE
 	 * guest R13 saved in SPRN_SCRATCH0
 	 */
 	std	r9, HSTATE_SCRATCH2(r13)
@@ -1367,12 +1366,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 11:	stw	r3,VCPU_HEIR(r9)
 
 	/* these are volatile across C function calls */
-#ifdef CONFIG_RELOCATABLE
-	ld	r3, HSTATE_SCRATCH1(r13)
-	mtctr	r3
-#else
 	mfctr	r3
-#endif
 	mfxer	r4
 	std	r3, VCPU_CTR(r9)
 	std	r4, VCPU_XER(r9)
@@ -3258,7 +3252,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_P9_TM_HV_ASSIST)
  * r12 is (CR << 32) | vector
  * r13 points to our PACA
  * r12 is saved in HSTATE_SCRATCH0(r13)
- * ctr is saved in HSTATE_SCRATCH1(r13) if RELOCATABLE
  * r9 is saved in HSTATE_SCRATCH2(r13)
  * r13 is saved in HSPRG1
  * cfar is saved in HSTATE_CFAR(r13)
@@ -3307,11 +3300,7 @@ kvmppc_bad_host_intr:
 	ld	r5, HSTATE_CFAR(r13)
 	std	r5, ORIG_GPR3(r1)
 	mflr	r3
-#ifdef CONFIG_RELOCATABLE
-	ld	r4, HSTATE_SCRATCH1(r13)
-#else
 	mfctr	r4
-#endif
 	mfxer	r5
 	lbz	r6, PACAIRQSOFTMASK(r13)
 	std	r3, _LINK(r1)

arch/powerpc/kvm/book3s_segment.S

@@ -167,16 +167,9 @@ kvmppc_interrupt_pr:
 	 * R12             = (guest CR << 32) | exit handler id
 	 * R13             = PACA
 	 * HSTATE.SCRATCH0 = guest R12
-	 * HSTATE.SCRATCH1 = guest CTR if RELOCATABLE
 	 */
 #ifdef CONFIG_PPC64
 	/* Match 32-bit entry */
-#ifdef CONFIG_RELOCATABLE
-	std	r9, HSTATE_SCRATCH2(r13)
-	ld	r9, HSTATE_SCRATCH1(r13)
-	mtctr	r9
-	ld	r9, HSTATE_SCRATCH2(r13)
-#endif
 	rotldi	r12, r12, 32		  /* Flip R12 halves for stw */
 	stw	r12, HSTATE_SCRATCH1(r13) /* CR is now in the low half */
 	srdi	r12, r12, 32		  /* shift trap into low half */