[PATCH 5/5] KVM: arm64: nVHE: Remove unneeded isb() when modifying PMSCR_EL1

[Alexandru Elisei]

According to ARM DDI 0487G.a, page D9-2930, profiling is disabled when
the PE is executing at a higher exception level than the profiling
buffer owning exception level. This is also confirmed by the pseudocode
for the StatisticalProfilingEnabled() function.

During the world switch and before activating guest traps, KVM executes
at EL2 with the buffer owning exception level being EL1 (MDCR_EL2.E2PB =
0b11). As a result, profiling is already disabled when draining the
buffer, making the isb() after the write to PMSCR_EL1 unnecessary.

CC: Will Deacon <will at kernel.org>
Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arch/arm64/kvm/hyp/nvhe/debug-sr.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index 7d3f25868cae..fdf0e0ba17e9 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -33,7 +33,6 @@ static void __debug_save_spe(u64 *pmscr_el1)
 	/* Yes; save the control register and disable data generation */
 	*pmscr_el1 = read_sysreg_s(SYS_PMSCR_EL1);
 	write_sysreg_s(0, SYS_PMSCR_EL1);
-	isb();
 
 	/* Now drain all buffered data to memory */
 	psb_csync();
-- 
2.32.0