linux-kernel - [PATCH 6/7] irqchip/gic-v3-its: Honor hypervisor enforced LPI range

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Message-Id: <20180620135234.32101-7-marc.zyngier@arm.com>
Date:   Wed, 20 Jun 2018 14:52:33 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Shanker Donthineni <shankerd@...eaurora.org>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        MaJun <majun258@...wei.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Lei Zhang <zhang.lei@...fujitsu.com>
Subject: [PATCH 6/7] irqchip/gic-v3-its: Honor hypervisor enforced LPI range

A recent extension to the GIC architecture allows a hypervisor to
arbitrarily reduce the number of LPIs available to a guest, no
matter what the GIC says about the valid range of IntIDs.

Let's factor in this information when computing the number of
available LPIs

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
---
 drivers/irqchip/irq-gic-v3-its.c   | 9 +++++++++
 include/linux/irqchip/arm-gic-v3.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 8c7e8c235faf..903ca1c19553 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1525,8 +1525,17 @@ static int free_lpi_range(u32 base, u32 nr_lpis)
 static int __init its_lpi_init(u32 id_bits)
 {
 	u32 lpis = (1UL << id_bits) - 8192;
+	u32 numlpis;
 	int err;
 
+	numlpis = 1UL << GICD_TYPER_NUM_LPIS(gic_rdists->gicd_typer);
+
+	if (numlpis > 1 && !WARN_ON(numlpis > lpis)) {
+		lpis = numlpis;
+		pr_info("ITS: Using hypervisor restricted LPI range [%u]\n",
+			lpis);
+	}
+
 	/*
 	 * Initializing the allocator is just the same as freeing the
 	 * full range of LPIs.
diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
index 396cd99af02f..9d2ea3e907d0 100644
--- a/include/linux/irqchip/arm-gic-v3.h
+++ b/include/linux/irqchip/arm-gic-v3.h
@@ -73,6 +73,7 @@
 #define GICD_TYPER_MBIS			(1U << 16)
 
 #define GICD_TYPER_ID_BITS(typer)	((((typer) >> 19) & 0x1f) + 1)
+#define GICD_TYPER_NUM_LPIS(typer)	((((typer) >> 11) & 0x1f) + 1)
 #define GICD_TYPER_IRQS(typer)		((((typer) & 0x1f) + 1) * 32)
 
 #define GICD_IROUTER_SPI_MODE_ONE	(0U << 31)
-- 
2.17.1