KVM: arm64: Add handler for MOPS exceptions

An Armv8.8 FEAT_MOPS main or epilogue instruction will take an exception
if executed on a CPU with a different MOPS implementation option (A or
B) than the CPU where the preceding prologue instruction ran. In this
case the OS exception handler is expected to reset the registers and
restart execution from the prologue instruction.

A KVM guest may use the instructions at EL1 at times when the guest is
not able to handle the exception, expecting that the instructions will
only run on one CPU (e.g. when running UEFI boot services in the guest).
As KVM may reschedule the guest between different types of CPUs at any
time (on an asymmetric system), it needs to also handle the resulting
exception itself in case the guest is not able to. A similar situation
will also occur in the future when live migrating a guest from one type
of CPU to another.

Add handling for the MOPS exception to KVM. The handling can be shared
with the EL0 exception handler, as the logic and register layouts are
the same. The exception can be handled right after exiting a guest,
which avoids the cost of returning to the host exit handler.

Similarly to the EL0 exception handler, in case the main or epilogue
instruction is being single stepped, it makes sense to finish the step
before executing the prologue instruction, so advance the single step
state machine.

Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230922112508.1774352-2-kristina.martsenko@arm.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

1 files changed, 1 insertions, 47 deletions

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 8b70759cdbb9..ede65a20e7dc 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -516,53 +516,7 @@ void do_el1_fpac(struct pt_regs *regs, unsigned long esr)
 
 void do_el0_mops(struct pt_regs *regs, unsigned long esr)
 {
-	bool wrong_option = esr & ESR_ELx_MOPS_ISS_WRONG_OPTION;
-	bool option_a = esr & ESR_ELx_MOPS_ISS_OPTION_A;
-	int dstreg = ESR_ELx_MOPS_ISS_DESTREG(esr);
-	int srcreg = ESR_ELx_MOPS_ISS_SRCREG(esr);
-	int sizereg = ESR_ELx_MOPS_ISS_SIZEREG(esr);
-	unsigned long dst, src, size;
-
-	dst = pt_regs_read_reg(regs, dstreg);
-	src = pt_regs_read_reg(regs, srcreg);
-	size = pt_regs_read_reg(regs, sizereg);
-
-	/*
-	 * Put the registers back in the original format suitable for a
-	 * prologue instruction, using the generic return routine from the
-	 * Arm ARM (DDI 0487I.a) rules CNTMJ and MWFQH.
-	 */
-	if (esr & ESR_ELx_MOPS_ISS_MEM_INST) {
-		/* SET* instruction */
-		if (option_a ^ wrong_option) {
-			/* Format is from Option A; forward set */
-			pt_regs_write_reg(regs, dstreg, dst + size);
-			pt_regs_write_reg(regs, sizereg, -size);
-		}
-	} else {
-		/* CPY* instruction */
-		if (!(option_a ^ wrong_option)) {
-			/* Format is from Option B */
-			if (regs->pstate & PSR_N_BIT) {
-				/* Backward copy */
-				pt_regs_write_reg(regs, dstreg, dst - size);
-				pt_regs_write_reg(regs, srcreg, src - size);
-			}
-		} else {
-			/* Format is from Option A */
-			if (size & BIT(63)) {
-				/* Forward copy */
-				pt_regs_write_reg(regs, dstreg, dst + size);
-				pt_regs_write_reg(regs, srcreg, src + size);
-				pt_regs_write_reg(regs, sizereg, -size);
-			}
-		}
-	}
-
-	if (esr & ESR_ELx_MOPS_ISS_FROM_EPILOGUE)
-		regs->pc -= 8;
-	else
-		regs->pc -= 4;
+	arm64_mops_reset_regs(&regs->user_regs, esr);
 
 	/*
 	 * If single stepping then finish the step before executing the