s390/kvm: fix interrupt race with HANDLE_SIE_INTERCEPT (dcd2a9aa) · Commits · 戴 / test

The HANDLE_SIE_INTERCEPT macro is used in the interrupt handlers and the program check handler to undo a few changes done by sie64a. Among them are guest vs host LPP, the gmap ASCE vs kernel ASCE and the bit that indicates that SIE is currently running on the CPU. There is a race of a voluntary SIE exit vs asynchronous interrupts. If the CPU completed the SIE instruction and the TM instruction of the LPP macro at the time it receives an interrupt, the interrupt handler will run while the LPP, the ASCE and the SIE bit are still set up for guest execution. This might result in wrong sampling data, but it will not cause data corruption or lockups. The critical section in sie64a needs to be enlarged to include all instructions that undo the changes required for guest execution. Signed-off-by:

Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

+4 −10

Original line number	Diff line number	Diff line
		@@ -90,14 +90,7 @@ _PIF_WORK = (_PIF_PER_TRAP)
		lgr \scratch,%r9
		slg \scratch,BASED(.Lsie_critical)
		clg \scratch,BASED(.Lsie_critical_length)
		.if \reason==1
		# Some program interrupts are suppressing (e.g. protection).
		# We must also check the instruction after SIE in that case.
		# do_protection_exception will rewind to .Lrewind_pad
		jh .+42
		.else
		jhe .+42
		.endif
		lg %r14,__SF_EMPTY(%r15) # get control block pointer
		LPP __SF_EMPTY+16(%r15) # set host id
		ni __SIE_PROG0C+3(%r14),0xfe # no longer in SIE
		@@ -1308,15 +1301,16 @@ ENTRY(sie64a)
		lg %r14,__SF_EMPTY(%r15) # get control block pointer
		oi __SIE_PROG0C+3(%r14),1 # we are going into SIE now
		tm __SIE_PROG20+3(%r14),3 # last exit...
		jnz .Lsie_done
		jnz .Lsie_skip
		tm __LC_CPU_FLAGS+7,_CIF_FPU
		jo .Lsie_done # exit if fp/vx regs changed
		jo .Lsie_skip # exit if fp/vx regs changed
		LPP __SF_EMPTY(%r15) # set guest id
		sie 0(%r14)
		.Lsie_done:
		LPP __SF_EMPTY+16(%r15) # set host id
		.Lsie_skip:
		ni __SIE_PROG0C+3(%r14),0xfe # no longer in SIE
		lctlg %c1,%c1,__LC_USER_ASCE # load primary asce
		.Lsie_done:
		# some program checks are suppressing. C code (e.g. do_protection_exception)
		# will rewind the PSW by the ILC, which is 4 bytes in case of SIE. Other
		# instructions between sie64a and .Lsie_done should not cause program

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