linux-kernel - [PATCH] clocksource/arm_arch_timer: Store physical timer IRQ number for KVM on VHE

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Date:   Thu, 24 Jan 2019 14:46:12 +0100
From:   Christoffer Dall <christoffer.dall@....com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        Andre Przywara <andre.przywara@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@....com>
Subject: [PATCH] clocksource/arm_arch_timer: Store physical timer IRQ number for KVM on VHE

From: Andre Przywara <andre.przywara@....com>

A host running in VHE mode gets the EL2 physical timer as its time
source (accessed using the EL1 sysreg accessors, which get re-directed
to the EL2 sysregs by VHE).

The EL1 physical timer remains unused by the host kernel, allowing us to
pass that on directly to a KVM guest and saves us from emulating this
timer for the guest on VHE systems.

Store the EL1 Physical Timer's IRQ number in
struct arch_timer_kvm_info on VHE systems to allow KVM to use it.

Signed-off-by: Andre Przywara <andre.przywara@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Christoffer Dall <christoffer.dall@....com>
---
Patches in preparation for nested virtualization on KVM/Arm depend on this
change, so we would like to merge this via the kvmarm tree or have a stable
branch including this patch.

Please let us know your preference.  Thanks.

 drivers/clocksource/arm_arch_timer.c | 11 +++++++++--
 include/clocksource/arm_arch_timer.h |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 9a7d4dc00b6e..b9243e2328b4 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -1206,6 +1206,13 @@ static enum arch_timer_ppi_nr __init arch_timer_select_ppi(void)
 	return ARCH_TIMER_PHYS_SECURE_PPI;
 }
 
+static void __init arch_timer_populate_kvm_info(void)
+{
+	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
+	if (is_kernel_in_hyp_mode())
+		arch_timer_kvm_info.physical_irq = arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI];
+}
+
 static int __init arch_timer_of_init(struct device_node *np)
 {
 	int i, ret;
@@ -1220,7 +1227,7 @@ static int __init arch_timer_of_init(struct device_node *np)
 	for (i = ARCH_TIMER_PHYS_SECURE_PPI; i < ARCH_TIMER_MAX_TIMER_PPI; i++)
 		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
 
-	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
+	arch_timer_populate_kvm_info();
 
 	rate = arch_timer_get_cntfrq();
 	arch_timer_of_configure_rate(rate, np);
@@ -1550,7 +1557,7 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
 	arch_timer_ppi[ARCH_TIMER_HYP_PPI] =
 		acpi_gtdt_map_ppi(ARCH_TIMER_HYP_PPI);
 
-	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
+	arch_timer_populate_kvm_info();
 
 	/*
 	 * When probing via ACPI, we have no mechanism to override the sysreg
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index 349e5957c949..702967d996bb 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -74,6 +74,7 @@ enum arch_timer_spi_nr {
 struct arch_timer_kvm_info {
 	struct timecounter timecounter;
 	int virtual_irq;
+	int physical_irq;
 };
 
 struct arch_timer_mem_frame {
-- 
2.18.0