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arm64: mm: Add confidential computing hook to ioremap_prot()

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Confidential Computing environments such as pKVM and Arm's CCA
distinguish between shared (i.e. emulated) and private (i.e. assigned)
MMIO regions.

Introduce a hook into our implementation of ioremap_prot() so that MMIO
regions can be shared if necessary.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240830130150.8568-6-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2024-08-30 14:01:48 +01:00
parent ebc59b120c
commit c86fa3470c
2 changed files with 26 additions and 1 deletions
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4
arch/arm64/include/asm/io.h
View File

@ -271,6 +271,10 @@ __iowrite64_copy(void __iomem *to, const void *from, size_t count)
* I/O memory mapping functions.
*/
typedef int (*ioremap_prot_hook_t)(phys_addr_t phys_addr, size_t size,
pgprot_t *prot);
int arm64_ioremap_prot_hook_register(const ioremap_prot_hook_t hook);
#define ioremap_prot ioremap_prot
#define _PAGE_IOREMAP PROT_DEVICE_nGnRE

23
arch/arm64/mm/ioremap.c
View File

@ -3,10 +3,22 @@
#include <linux/mm.h>
#include <linux/io.h>
static ioremap_prot_hook_t ioremap_prot_hook;
int arm64_ioremap_prot_hook_register(ioremap_prot_hook_t hook)
{
if (WARN_ON(ioremap_prot_hook))
return -EBUSY;
ioremap_prot_hook = hook;
return 0;
}
void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
unsigned long prot)
{
unsigned long last_addr = phys_addr + size - 1;
pgprot_t pgprot = __pgprot(prot);
/* Don't allow outside PHYS_MASK */
if (last_addr & ~PHYS_MASK)
@ -16,7 +28,16 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
if (WARN_ON(pfn_is_map_memory(__phys_to_pfn(phys_addr))))
return NULL;
return generic_ioremap_prot(phys_addr, size, __pgprot(prot));
/*
* If a hook is registered (e.g. for confidential computing
* purposes), call that now and barf if it fails.
*/
if (unlikely(ioremap_prot_hook) &&
WARN_ON(ioremap_prot_hook(phys_addr, size, &pgprot))) {
return NULL;
}
return generic_ioremap_prot(phys_addr, size, pgprot);
}
EXPORT_SYMBOL(ioremap_prot);