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SubjectRe: [PATCH v5 1/2] x86/kexec: Build identity mapping for EFI systab and ACPI tables
On Wed, Apr 24, 2019 at 05:29:43PM +0800, Baoquan He wrote:
> From: Kairui Song <kasong@redhat.com>
>
> The current code only builds identity mapping for physical memory during
> kexec-type loading. The regions reserved by firmware are not covered.
> In the next patch, the boot decompressing code of kexec-ed kernel tries

There's no guarantee that when this patch gets applied, the next patch
will be the one you mean. So explain what you mean here instead.

> to access EFI systab and ACPI tables, lacking identity mapping for them
> will cause error and reset system to firmware.
>
> This error doesn't happen on all systems. Because kexec enables gbpages
> to build identity mapping, the EFI systab and ACPI tables could have been
> covered if they share the same 1 GB area with physical memory. To make
> sure, we should map them always.
>
> So here add mapping for them.
>
> Signed-off-by: Kairui Song <kasong@redhat.com>

When you send someone else's patch, you need to add your SOB. Lemme
point you to

Documentation/process/submitting-patches.rst

again. Please have a deeper look.

> ---
> arch/x86/kernel/machine_kexec_64.c | 86 ++++++++++++++++++++++++++++++
> 1 file changed, 86 insertions(+)
>
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index ceba408ea982..77b40c3e28d7 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -18,6 +18,7 @@
> #include <linux/io.h>
> #include <linux/suspend.h>
> #include <linux/vmalloc.h>
> +#include <linux/efi.h>
>
> #include <asm/init.h>
> #include <asm/pgtable.h>
> @@ -29,6 +30,48 @@
> #include <asm/setup.h>
> #include <asm/set_memory.h>
>
> +#ifdef CONFIG_ACPI
> +/**

Two stars '**' are kernel-doc style but this comment is implementation
detail and is irrelevant for kernel-doc ouput.

> + * Used while adding mapping for ACPI tables.
> + * Can be reused when other iomem regions need be mapped
> + */
> +struct init_pgtable_data {
> + struct x86_mapping_info *info;
> + pgd_t *level4p;
> +};
> +
> +static int mem_region_callback(struct resource *res, void *arg)
> +{
> + struct init_pgtable_data *data = arg;
> + unsigned long mstart, mend;
> +
> + mstart = res->start;
> + mend = mstart + resource_size(res) - 1;
> +
> + return kernel_ident_mapping_init(data->info,
> + data->level4p, mstart, mend);

Do not break that line.

> +}
> +
> +static int init_acpi_pgtable(struct x86_mapping_info *info,
> + pgd_t *level4p)

static int
map_acpi_tables(...)

> +{
> + unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + struct init_pgtable_data data;
> +
> + data.info = info;
> + data.level4p = level4p;
> + flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + return walk_iomem_res_desc(IORES_DESC_ACPI_TABLES, flags, 0, -1,
> + &data, mem_region_callback);
> +}
> +#else
> +static int init_acpi_pgtable(struct x86_mapping_info *info,
> + pgd_t *level4p)
> +{
> + return 0;
> +}
> +#endif
> +
> #ifdef CONFIG_KEXEC_FILE
> const struct kexec_file_ops * const kexec_file_loaders[] = {
> &kexec_bzImage64_ops,
> @@ -36,6 +79,37 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
> };
> #endif
>
> +#ifdef CONFIG_EFI
> +static int init_efi_systab_pgtable(struct x86_mapping_info *info,
> + pgd_t *level4p)

This function's name is wrong. Make it like this:

static int
map_efi_systab(struct x86_mapping_info *info, pgd_t *level4p)
{
#ifdef CONFIG_EFI

...

#endif

return 0;
}

and drop the #else ifdeffery.


> +{
> + unsigned long mstart, mend;
> +
> + if (!efi_enabled(EFI_BOOT))
> + return 0;
> +
> + mstart = (boot_params.efi_info.efi_systab |
> + ((u64)boot_params.efi_info.efi_systab_hi<<32));
> +
> + if (efi_enabled(EFI_64BIT))
> + mend = mstart + sizeof(efi_system_table_64_t);
> + else
> + mend = mstart + sizeof(efi_system_table_32_t);
> +
> + if (mstart)
> + return kernel_ident_mapping_init(info,
> + level4p, mstart, mend);

Flip that logic:

if (!mstart)
return 0;

return kernel_ident_mapping_init(info, level4p, mstart, mend);

and let the function stick out.

> +
> + return 0;
> +}
> +#else
> +static inline int init_efi_systab_pgtable(struct x86_mapping_info *info,
> + pgd_t *level4p)
> +{
> + return 0;
> +}
> +#endif
> +
> static void free_transition_pgtable(struct kimage *image)
> {
> free_page((unsigned long)image->arch.p4d);
> @@ -159,6 +233,18 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
> return result;
> }
>
> + /**

Two stars '**' are kernel-doc style comments above function names but
not here.

> + * Prepare EFI systab and ACPI table mapping for kexec kernel,
> + * since they are not covered by pfn_mapped.
> + */
> + result = init_efi_systab_pgtable(&info, level4p);
> + if (result)
> + return result;
> +
> + result = init_acpi_pgtable(&info, level4p);
> + if (result)
> + return result;
> +
> return init_transition_pgtable(image, level4p);
> }
>
> --
> 2.17.2
>

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.
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