Hi Ard,
On 6/10/2019 8:05 AM, Ard Biesheuvel wrote:
> Ensure that the EFI memreserve entries can be accessed, even if they
> are located in memory that the kernel (e.g., a crashkernel) omits from
> the linear map.
>
> Reported-by: Jonathan Richardson <jonathan.richardson@xxxxxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Does it make sense to add a Fixes tag?
> ---
> drivers/firmware/efi/efi.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 16b2137d117c..4b7cf7bc0ded 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -1009,14 +1009,16 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
>
> /* first try to find a slot in an existing linked list entry */
> for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
> - rsv = __va(prsv);
> + rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
> index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
> if (index < rsv->size) {
> rsv->entry[index].base = addr;
> rsv->entry[index].size = size;
>
> + memunmap(rsv);
> return 0;
> }
> + memunmap(rsv);
> }
>
> /* no slot found - allocate a new linked list entry */
> @@ -1024,7 +1026,13 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
> if (!rsv)
> return -ENOMEM;
>
> - rsv->size = EFI_MEMRESERVE_COUNT(PAGE_SIZE);
> + /*
> + * The memremap() call above assumes that a linux_efi_memreserve entry
> + * never crosses a page boundary, so let's ensure that this remains true
> + * even when kexec'ing a 4k pages kernel from a >4k pages kernel, by
> + * using SZ_4K explicitly in the size calculation below.
> + */
> + rsv->size = EFI_MEMRESERVE_COUNT(SZ_4K);
> atomic_set(&rsv->count, 1);
> rsv->entry[0].base = addr;
> rsv->entry[0].size = size;
>
