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    SubjectRe: [PATCH 2/2] efi/esrt: mark ESRT memory region as nomap
    On 02/23/18 at 12:42pm, Tyler Baicar wrote:
    > The ESRT memory region is being exposed as System RAM in /proc/iomem
    > which is wrong because it cannot be overwritten. This memory is needed
    > for kexec kernels in order to properly initialize ESRT, so if it is
    > overwritten it will cause ESRT failures in the kexec kernel. Mark this
    > region as nomap so that it is not overwritten.
    >
    > Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
    > Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
    > ---
    > drivers/firmware/efi/esrt.c | 8 ++++++++
    > 1 file changed, 8 insertions(+)
    >
    > diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
    > index 504f3c3..f5f79c7 100644
    > --- a/drivers/firmware/efi/esrt.c
    > +++ b/drivers/firmware/efi/esrt.c
    > @@ -335,6 +335,14 @@ void __init efi_esrt_init(void)
    > pr_info("Reserving ESRT space from %pa to %pa.\n", &esrt_data, &end);
    > efi_mem_reserve(esrt_data, esrt_data_size);
    >
    > + /*
    > + * Mark the ESRT memory region as nomap to avoid it being exposed as
    > + * System RAM in /proc/iomem. Otherwise this block can be overwritten
    > + * which will then cause failures in kexec'd kernels since the ESRT
    > + * information is no longer there.
    > + */
    > + memblock_mark_nomap(esrt_data, esrt_data_size);
    > +

    On my X86 machine, esrt region was marked as reserved /proc/iomem,
    this issue could be a arm64 only problem, it is better to handle this in
    arm init code.


    > pr_debug("esrt-init: loaded.\n");
    > err_memunmap:
    > early_memunmap(va, size);
    > --
    > Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
    > Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
    > a Linux Foundation Collaborative Project.
    >
    > --
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    Thanks
    Dave

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