linux-kernel - [PATCH RT] arm64: Allow selecting KVM and PREEMPT

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Date:   Tue, 23 Nov 2021 10:59:28 +0100
From:   Nicolas Saenz Julienne <nsaenzju@...hat.com>
To:     bigeasy@...utronix.de, linux-rt-users@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        mtosatti@...hat.com, juri.lelli@...hat.com,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>
Subject: [PATCH RT] arm64: Allow selecting KVM and PREEMPT_RT

With 6caa5812e2d1 ("KVM: arm64: Use generic KVM xfer to guest work
function") all arm64 exit paths are properly equipped to handle the
POSIX timers' task work.

And with a68773bd32d9 ("arm64: Select POSIX_CPU_TIMERS_TASK_WORK") we
now handle the timers in thread context.

This allows for KVM and PREEMPT_RT to coexist, so update Kconfig to
reflect that.

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@...hat.com>
---

I guess this could be squashed into 19614b91cc83 ("ARM64: Allow to
enable RT")

Note: I did test this on an Ampere Mt. Jade based machine.

 arch/arm64/Kconfig | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6bd4acc2be02..260866cf53c9 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -89,7 +89,7 @@ config ARM64
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
 	select ARCH_SUPPORTS_NUMA_BALANCING
-	select ARCH_SUPPORTS_RT if HAVE_POSIX_CPU_TIMERS_TASK_WORK
+	select ARCH_SUPPORTS_RT
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
 	select ARCH_WANT_DEFAULT_BPF_JIT
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
@@ -216,7 +216,6 @@ config ARM64
 	select PCI_DOMAINS_GENERIC if PCI
 	select PCI_ECAM if (ACPI && PCI)
 	select PCI_SYSCALL if PCI
-	select HAVE_POSIX_CPU_TIMERS_TASK_WORK if !KVM
 	select POWER_RESET
 	select POWER_SUPPLY
 	select SPARSE_IRQ
-- 
2.33.1