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    Subject[PATCH 5.16 0026/1039] riscv: Dont use va_pa_offset on kdump
    Date
    From: Nick Kossifidis <mick@ics.forth.gr>

    commit a11c07f032a0e9a562a32ece73af96b0e754c4b3 upstream.

    On kdump instead of using an intermediate step to relocate the kernel,
    that lives in a "control buffer" outside the current kernel's mapping,
    we jump to the crash kernel directly by calling riscv_kexec_norelocate().
    The current implementation uses va_pa_offset while switching to physical
    addressing, however since we moved the kernel outside the linear mapping
    this won't work anymore since riscv_kexec_norelocate() is part of the
    kernel mapping and we should use kernel_map.va_kernel_pa_offset, and also
    take XIP kernel into account.

    We don't really need to use va_pa_offset on riscv_kexec_norelocate, we
    can just set STVEC to the physical address of the new kernel instead and
    let the hart jump to the new kernel on the next instruction after setting
    SATP to zero. This fixes kdump and is also simpler/cleaner.

    I tested this on the latest qemu and HiFive Unmatched and works as
    expected.

    Fixes: 2bfc6cd81bd1 ("riscv: Move kernel mapping outside of linear mapping")
    Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
    Reviewed-by: Alexandre Ghiti <alex@ghiti.fr>
    Cc: stable@vger.kernel.org
    Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/riscv/kernel/kexec_relocate.S | 20 +++++++++-----------
    1 file changed, 9 insertions(+), 11 deletions(-)

    --- a/arch/riscv/kernel/kexec_relocate.S
    +++ b/arch/riscv/kernel/kexec_relocate.S
    @@ -159,25 +159,15 @@ SYM_CODE_START(riscv_kexec_norelocate)
    * s0: (const) Phys address to jump to
    * s1: (const) Phys address of the FDT image
    * s2: (const) The hartid of the current hart
    - * s3: (const) kernel_map.va_pa_offset, used when switching MMU off
    */
    mv s0, a1
    mv s1, a2
    mv s2, a3
    - mv s3, a4

    /* Disable / cleanup interrupts */
    csrw CSR_SIE, zero
    csrw CSR_SIP, zero

    - /* Switch to physical addressing */
    - la s4, 1f
    - sub s4, s4, s3
    - csrw CSR_STVEC, s4
    - csrw CSR_SATP, zero
    -
    -.align 2
    -1:
    /* Pass the arguments to the next kernel / Cleanup*/
    mv a0, s2
    mv a1, s1
    @@ -214,7 +204,15 @@ SYM_CODE_START(riscv_kexec_norelocate)
    csrw CSR_SCAUSE, zero
    csrw CSR_SSCRATCH, zero

    - jalr zero, a2, 0
    + /*
    + * Switch to physical addressing
    + * This will also trigger a jump to CSR_STVEC
    + * which in this case is the address of the new
    + * kernel.
    + */
    + csrw CSR_STVEC, a2
    + csrw CSR_SATP, zero
    +
    SYM_CODE_END(riscv_kexec_norelocate)

    .section ".rodata"

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