From: Suzuki K Poulose <suzuki.poulose@arm.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.
Future changes could filter the physical address and make the
decision accordingly.

Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/fixmap.h |  4 +++-
 arch/arm64/mm/mmu.c             | 13 +++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 87e307804b99..f765943b088c 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -107,7 +107,9 @@ void __init early_fixmap_init(void);
 #define __late_set_fixmap __set_fixmap
 #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);
+void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
 
 #include <asm-generic/fixmap.h>
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 495b732d5af3..79d84db9ffcb 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1179,6 +1179,19 @@ 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;
+
+	/*
+	 * For now we consider all I/O as non-secure. For future
+	 * filter the I/O base for setting appropriate permissions.
+	 */
+	prot = __pgprot(pgprot_val(prot) | PROT_NS_SHARED);
+
+	return __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

On Fri, Apr 12, 2024 at 09:42:05AM +0100, Steven Price wrote:
> 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.
> Future changes could filter the physical address and make the
> decision accordingly.
[...]
> +void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys)
> +{
> +	pgprot_t prot = FIXMAP_PAGE_IO;
> +
> +	/*
> +	 * For now we consider all I/O as non-secure. For future
> +	 * filter the I/O base for setting appropriate permissions.
> +	 */
> +	prot = __pgprot(pgprot_val(prot) | PROT_NS_SHARED);
> +
> +	return __set_fixmap(idx, phys, prot);
> +}

I looked through the patches and could not find any place where this
function does anything different as per the commit log suggestion. Can
we just update FIXMAP_PAGE_IO for now until you have a clear use-case?

-- 
Catalin

On 13/05/2024 17:14, Catalin Marinas wrote:
> On Fri, Apr 12, 2024 at 09:42:05AM +0100, Steven Price wrote:
>> 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.
>> Future changes could filter the physical address and make the
>> decision accordingly.
> [...]
>> +void set_fixmap_io(enum fixed_addresses idx, phys_addr_t phys)
>> +{
>> +	pgprot_t prot = FIXMAP_PAGE_IO;
>> +
>> +	/*
>> +	 * For now we consider all I/O as non-secure. For future
>> +	 * filter the I/O base for setting appropriate permissions.
>> +	 */
>> +	prot = __pgprot(pgprot_val(prot) | PROT_NS_SHARED);
>> +
>> +	return __set_fixmap(idx, phys, prot);
>> +}
> 
> I looked through the patches and could not find any place where this
> function does anything different as per the commit log suggestion. Can
> we just update FIXMAP_PAGE_IO for now until you have a clear use-case?
> 

This gets used by the earlycon mapping. The commit description could be
made clear.

We may have to revisit this code to optionally apply the PROT_NS_SHARED
attribute, depending on whether this is a "protected MMIO" or not.


Suzuki