On 13 September 2016 at 04:28, Chao Gao <chao.gao@xxxxxxxxx> wrote:
> Commit 78ce248f (efi: Iterate over efi.memmap in for_each_efi_memory_desc())
> replaces the old loop by for_each_efi_memory_desc() which will encounter #PF
> when efi.memap are not initialized.
>
> In boot process, xen set EFI_PARAVIRT in xen_efi_init() before setup_arch()
> is called. This leads efi_memmap_init() will not initialize structures
> related to efi.memmap. However, the following functions e.g.
> efi_find_mirror(), efi_print_memmap() and efi_free_boot_services() access
> efi.memmap without necessary checks. kernel and xen crash in this case.
> After adding these checks, xen and kernel boot up normally.
>
OK, so looking at the hunks below, it looks to me like we should
initialize the efi.memmap to sane values in the EFI_PARAVIRT case,
rather than open coding this test each time for_each_efi_memory_desc()
is invoked.
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> ---
> arch/x86/platform/efi/efi.c | 6 ++++++
> arch/x86/platform/efi/quirks.c | 3 +++
> 2 files changed, 9 insertions(+)
>
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 1fbb408..68966dc 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -102,6 +102,9 @@ void __init efi_find_mirror(void)
> efi_memory_desc_t *md;
> u64 mirror_size = 0, total_size = 0;
>
> + if (efi_enabled(EFI_PARAVIRT))
> + return;
> +
> for_each_efi_memory_desc(md) {
> unsigned long long start = md->phys_addr;
> unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
> @@ -207,6 +210,9 @@ void __init efi_print_memmap(void)
> efi_memory_desc_t *md;
> int i = 0;
>
> + if (efi_enabled(EFI_PARAVIRT))
> + return;
> +
> for_each_efi_memory_desc(md) {
> char buf[64];
>
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index 89d1146..4fa1e4d 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -251,6 +251,9 @@ void __init efi_free_boot_services(void)
> {
> efi_memory_desc_t *md;
>
> + if (efi_enabled(EFI_PARAVIRT))
> + return;
> +
> for_each_efi_memory_desc(md) {
> unsigned long long start = md->phys_addr;
> unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
> --
> 1.8.3.1
>
> --
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