Commit c86fa347 authored by Will Deacon's avatar Will Deacon
Browse files

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



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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240830130150.8568-6-will@kernel.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent ebc59b12

arch/arm64/include/asm/io.h

+4 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/mm/ioremap.c

+22 −1
Original line number Diff line number Diff line
@@ -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);