linux-kernel - [PATCH v2 16/16] arm64: Register earlycon fixmap with the MMIO guard

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Date:   Mon,  4 Oct 2021 18:48:49 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, qperret@...gle.com, dbrazdil@...gle.com,
        Steven Price <steven.price@....com>,
        Andrew Jones <drjones@...hat.com>,
        Fuad Tabba <tabba@...gle.com>,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH v2 16/16] arm64: Register earlycon fixmap with the MMIO guard

On initialising the MMIO guard infrastructure, register the
earlycon mapping if present.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/mm/ioremap.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
index 62b715ea31e5..0e10b788500c 100644
--- a/arch/arm64/mm/ioremap.c
+++ b/arch/arm64/mm/ioremap.c
@@ -39,6 +39,17 @@ static int __init ioremap_guard_setup(char *str)
 }
 early_param("ioremap_guard", ioremap_guard_setup);
 
+static void fixup_fixmap(void)
+{
+	pte_t *ptep = __get_fixmap_pte(FIX_EARLYCON_MEM_BASE);
+
+	if (!ptep)
+		return;
+
+	ioremap_phys_range_hook(__pte_to_phys(*ptep), PAGE_SIZE,
+				__pgprot(pte_val(*ptep) & PTE_ATTRINDX_MASK));
+}
+
 void kvm_init_ioremap_services(void)
 {
 	struct arm_smccc_res res;
@@ -62,6 +73,7 @@ void kvm_init_ioremap_services(void)
 			     &res);
 	if (res.a0 == SMCCC_RET_SUCCESS) {
 		static_branch_enable(&ioremap_guard_key);
+		fixup_fixmap();
 		pr_info("Using KVM MMIO guard for ioremap\n");
 	} else {
 		pr_warn("KVM MMIO guard registration failed (%ld)\n", res.a0);
-- 
2.30.2