Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

Dave Young
2019-04-24T06:18:42Z

On 04/24/19 at 01:41pm, Baoquan He wrote:
> On 04/24/19 at 02:47am, Junichi Nomura wrote:
> > On 4/24/19 2:15 AM, Kairui Song wrote:
> > > On Mon, Apr 22, 2019 at 11:21 PM Junichi Nomura <j-nomura@ce.jp.nec.com> wrote:
> > >> Is the mapping of ACPI tables just by luck, too?
> > >
> > > Good question, they should have same issue with systab, I ignored this one.
> > > Then in first kernel when doing kexec it should ensure both ACPI
> > > tables and the EFI systab are mapped, that should cover everything and
> > > make it work.
> >
> > Right.
> >
> > > Is there anything else missing?
> > No, as far as I looked around get_rsdp_addr().
>
> Have made a draft patch to build ident mapping for ACPI tables too, it's
> based on Kairui's patch. Dave has tested on his t400s laptop, and
> passed. Please check if this adding is OK.
>
> Kairui, you can add this into your patch to make a new one and resend.
> Or I can combine them and send for you today.
>
> From 7f17fcb12a6fddbb0f5e56e5137cc81f25c04af4 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@redhat.com>
> Date: Wed, 24 Apr 2019 09:57:01 +0800
> Subject: [PATCH] x86/kexec: Prepare ACPI table mapping for kexec kernel
>
> If the kernel decompressing code accesses ACPI tabels in kexec-ed kernel,
> they also need be 1:1 mapped.
>
> ---
> arch/x86/kernel/machine_kexec_64.c | 54 ++++++++++++++++++++++++++++--
> 1 file changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index d5da54893f97..e2948aea27d4 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -30,6 +30,48 @@
> #include <asm/setup.h>
> #include <asm/set_memory.h>
>
> +#ifdef CONFIG_ACPI
> +/**
> + * 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);
> +}
> +
> +static int init_acpi_pgtable(struct x86_mapping_info *info,
> + pgd_t *level4p)
> +{
> + 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,
> @@ -114,6 +156,8 @@ static void *alloc_pgt_page(void *data)
> return p;
> }
>
> +
> +
> #ifdef CONFIG_EFI
> static int init_efi_systab_pgtable(struct x86_mapping_info *info,
> pgd_t *level4p)
> @@ -191,14 +235,18 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
> return result;
> }
>
> - /*
> - * Prepare EFI systab mapping for kexec kernel, systab is not
> - * covered by pfn_mapped.
> + /**
> + * 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
>

Since I can not reproduce the acpi table accessing fault with Kairui's patch,
the test is just sanity testing on same hardware. But the patch looks
good.

With Kairui's fix+ this acpi fix and Junichi's patch everything works.
Can anyone send them for example patch 1/2: kexec early mapping for
efi/acpi, patch 2/2: Junichi's previous patch.

With these fixes I think kexec will just work. Maybe we can go with
these fixes and leave other issues like the loader type flag etc as
future issue.

Thanks
Dave