On 15.01.21 09:32, Mike Rapoport wrote: > From: Mike Rapoport <r...@linux.ibm.com> > > The early reservations of memory areas used by the firmware, bootloader, > kernel text and data are spread over setup_arch(). Moreover, some of them > happen *after* memblock allocations, e.g trim_platform_memory_ranges() and > trim_low_memory_range() are called after reserve_real_mode() that allocates > memory. > > We did not observe corruption of these memory regions because memblock > always allocates memory either from the end of memory (in top-down mode) or > above the kernel image (in bottom-up mode). However, the bottom up mode is > going to be updated to span the entire memory [1] to avoid limitations > caused by KASLR. > > Consolidate early memory reservations in a dedicated function to improve > robustness against future changes. Having the early reservations in one > place also makes it clearer what memory must be reserved before we allow > memblock allocations. > > [1] https://lore.kernel.org/lkml/20201217201214.3414100-2-g...@fb.com > > Signed-off-by: Mike Rapoport <r...@linux.ibm.com> > --- > arch/x86/kernel/setup.c | 80 ++++++++++++++++++++++------------------- > 1 file changed, 44 insertions(+), 36 deletions(-) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 3412c4595efd..32cd2e790a0a 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -728,7 +728,38 @@ static void __init trim_low_memory_range(void) > */ > memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE)); > } > - > + > +static void __init early_reserve_memory(void) > +{ > + /* > + * Reserve the memory occupied by the kernel between _text and > + * __end_of_kernel_reserve symbols. Any kernel sections after the > + * __end_of_kernel_reserve symbol must be explicitly reserved with a > + * separate memblock_reserve() or they will be discarded. > + */ > + memblock_reserve(__pa_symbol(_text), > + (unsigned long)__end_of_kernel_reserve - (unsigned > long)_text); > + > + /* > + * Make sure page 0 is always reserved because on systems with > + * L1TF its contents can be leaked to user processes. > + */ > + memblock_reserve(0, PAGE_SIZE); > + > + early_reserve_initrd(); > + > + if (efi_enabled(EFI_BOOT)) > + efi_memblock_x86_reserve_range(); > + > + memblock_x86_reserve_range_setup_data(); > + > + reserve_ibft_region(); > + reserve_bios_regions(); > + > + trim_platform_memory_ranges(); > + trim_low_memory_range(); > +} > + > /* > * Dump out kernel offset information on panic. > */ > @@ -763,29 +794,6 @@ dump_kernel_offset(struct notifier_block *self, unsigned > long v, void *p) > > void __init setup_arch(char **cmdline_p) > { > - /* > - * Reserve the memory occupied by the kernel between _text and > - * __end_of_kernel_reserve symbols. Any kernel sections after the > - * __end_of_kernel_reserve symbol must be explicitly reserved with a > - * separate memblock_reserve() or they will be discarded. > - */ > - memblock_reserve(__pa_symbol(_text), > - (unsigned long)__end_of_kernel_reserve - (unsigned > long)_text); > - > - /* > - * Make sure page 0 is always reserved because on systems with > - * L1TF its contents can be leaked to user processes. > - */ > - memblock_reserve(0, PAGE_SIZE); > - > - early_reserve_initrd(); > - > - /* > - * At this point everything still needed from the boot loader > - * or BIOS or kernel text should be early reserved or marked not > - * RAM in e820. All other memory is free game. > - */ > - > #ifdef CONFIG_X86_32 > memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data)); > > @@ -909,8 +917,18 @@ void __init setup_arch(char **cmdline_p) > > parse_early_param(); > > - if (efi_enabled(EFI_BOOT)) > - efi_memblock_x86_reserve_range(); > + /* > + * Do some memory reservations *before* memory is added to > + * memblock, so memblock allocations won't overwrite it. > + * Do it after early param, so we could get (unlikely) panic from > + * serial. > + * > + * After this point everything still needed from the boot loader or > + * firmware or kernel text should be early reserved or marked not > + * RAM in e820. All other memory is free game. > + */ > + early_reserve_memory(); > + > #ifdef CONFIG_MEMORY_HOTPLUG > /* > * Memory used by the kernel cannot be hot-removed because Linux > @@ -937,9 +955,6 @@ void __init setup_arch(char **cmdline_p) > > x86_report_nx(); > > - /* after early param, so could get panic from serial */ > - memblock_x86_reserve_range_setup_data(); > - > if (acpi_mps_check()) { > #ifdef CONFIG_X86_LOCAL_APIC > disable_apic = 1; > @@ -1031,8 +1046,6 @@ void __init setup_arch(char **cmdline_p) > */ > find_smp_config(); > > - reserve_ibft_region(); > - > early_alloc_pgt_buf(); > > /* > @@ -1053,8 +1066,6 @@ void __init setup_arch(char **cmdline_p) > */ > sev_setup_arch(); > > - reserve_bios_regions(); > - > efi_fake_memmap(); > efi_find_mirror(); > efi_esrt_init(); > @@ -1080,9 +1091,6 @@ void __init setup_arch(char **cmdline_p) > > reserve_real_mode(); > > - trim_platform_memory_ranges(); > - trim_low_memory_range(); > - > init_mem_mapping(); > > idt_setup_early_pf(); >
Did not fully review for side-effects, but looks like a reasonable thing to do! -- Thanks, David / dhildenb
