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efi: Add a function to look up existing IO memory mappings

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The EFI initialization creates virtual mappings for EFI boot services
memory, so if a driver wants to access EFI boot services memory, it
cannot call ioremap itself; doing so will trip the WARN about mapping
RAM twice.  Thus, a driver accessing EFI boot services memory must do so
via the existing mapping already created during EFI intiialization.
Since the EFI code already maintains a memory map for that memory, add a
function efi_lookup_mapped_addr to look up mappings in that memory map.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: http://lkml.kernel.org/r/0eb48ae012797912874919110660ad420b90268b.1348876882.git.josh@joshtriplett.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Josh Triplett 2012-09-28 17:56:08 -07:00 committed by H. Peter Anvin
parent 785107923a
commit 7bc90e01c3
2 changed files with 29 additions and 0 deletions
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28
arch/x86/platform/efi/efi.c
View File

@ -776,6 +776,34 @@ static void __init runtime_code_page_mkexec(void)
}
}
/*
* We can't ioremap data in EFI boot services RAM, because we've already mapped
* it as RAM. So, look it up in the existing EFI memory map instead. Only
* callable after efi_enter_virtual_mode and before efi_free_boot_services.
*/
void __iomem *efi_lookup_mapped_addr(u64 phys_addr)
{
void *p;
if (WARN_ON(!memmap.map))
return NULL;
for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
efi_memory_desc_t *md = p;
u64 size = md->num_pages << EFI_PAGE_SHIFT;
u64 end = md->phys_addr + size;
if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
md->type != EFI_BOOT_SERVICES_CODE &&
md->type != EFI_BOOT_SERVICES_DATA)
continue;
if (!md->virt_addr)
continue;
if (phys_addr >= md->phys_addr && phys_addr < end) {
phys_addr += md->virt_addr - md->phys_addr;
return (__force void __iomem *)(unsigned long)phys_addr;
}
}
return NULL;
}
/*
* This function will switch the EFI runtime services to virtual mode.
* Essentially, look through the EFI memmap and map every region that

1
include/linux/efi.h
View File

@ -501,6 +501,7 @@ extern void efi_free_boot_services(void);
#else
static inline void efi_free_boot_services(void) {}
#endif
extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
extern u64 efi_get_iobase (void);
extern u32 efi_mem_type (unsigned long phys_addr);
extern u64 efi_mem_attributes (unsigned long phys_addr);