linux-kernel - [PATCH v5 10/19] arm64: Override set_fixmap

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Message-Id: <20240819131924.372366-11-steven.price@arm.com>
Date: Mon, 19 Aug 2024 14:19:15 +0100
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Cc: Steven Price <steven.price@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>,
	linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>
Subject: [PATCH v5 10/19] arm64: Override set_fixmap_io

From: Suzuki K Poulose <suzuki.poulose@....com>

Override the set_fixmap_io to set shared permission for the host
in case of a CC guest. For now we mark it shared unconditionally.

If/when support for device assignment and device emulation in the realm
is added in the future then this will need to filter the physical
address and make the decision accordingly.

Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Steven Price <steven.price@....com>
---
New patch for v5
---
 arch/arm64/include/asm/fixmap.h |  2 ++
 arch/arm64/mm/mmu.c             | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 87e307804b99..2c20da3a468c 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -108,6 +108,8 @@ void __init early_fixmap_init(void);
 #define __late_clear_fixmap(idx) __set_fixmap((idx), 0, FIXMAP_PAGE_CLEAR)
 
 extern void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
+#define set_fixmap_io set_fixmap_io
+void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys);
 
 #include <asm-generic/fixmap.h>
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 353ea5dc32b8..06b66c23c124 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1193,6 +1193,23 @@ void vmemmap_free(unsigned long start, unsigned long end,
 }
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
+void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys)
+{
+	pgprot_t prot = FIXMAP_PAGE_IO;
+
+	/*
+	 * The set_fixmap_io maps a single Page covering phys.
+	 * To make better decision, we stick to the smallest page
+	 * size supported (4K).
+	 */
+	if (!arm64_is_iomem_private(phys, SZ_4K))
+		prot = pgprot_decrypted(prot);
+	else
+		prot = pgprot_encrypted(prot);
+
+	__set_fixmap(idx, phys, prot);
+}
+
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 {
 	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
-- 
2.34.1