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Message-ID: <76385637-099e-45f5-b892-bd62c028926d@antgroup.com>
Date: Mon, 16 Sep 2024 11:10:45 +0800
From: "Tiwei Bie" <tiwei.btw@...group.com>
To: Benjamin Berg <benjamin@...solutions.net>, richard@....at,
anton.ivanov@...bridgegreys.com, johannes@...solutions.net
Cc: linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] um: Remove highmem leftovers
On 2024/9/16 00:55, Benjamin Berg wrote:
> Hi,
>
> does that mean we can also drop the 3-level page table support on i386?
> It seems like the two level page table is entirely sufficient on a
> system without high memory (i.e. only 32bit physical addresses).
Good point. I think so too.
Regards,
Tiwei
>
> When I took a look at it for the 4-level page table support on 64 bit I
> got a bit confused. But I had not realized that highmem support had
> been removed.
>
> Benjamin
>
> On Fri, 2024-09-13 at 22:21 +0800, Tiwei Bie wrote:
>> Highmem was only supported on UML/i386. And the support has been
>> removed by commit a98a6d864d3b ("um: Remove broken highmem support").
>> Remove the leftovers and stop UML from trying to setup highmem when
>> the sum of physmem_size and iomem_size exceeds max_physmem.
>>
>> Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
>> ---
>> arch/um/drivers/virtio_uml.c | 9 +--------
>> arch/um/include/shared/as-layout.h | 1 -
>> arch/um/include/shared/mem_user.h | 5 ++---
>> arch/um/kernel/mem.c | 3 ---
>> arch/um/kernel/physmem.c | 30 +++++++++++-----------------
>> --
>> arch/um/kernel/um_arch.c | 17 +++++++----------
>> 6 files changed, 21 insertions(+), 44 deletions(-)
>>
>> diff --git a/arch/um/drivers/virtio_uml.c
>> b/arch/um/drivers/virtio_uml.c
>> index 2b6e701776b6..e7f5556e3c96 100644
>> --- a/arch/um/drivers/virtio_uml.c
>> +++ b/arch/um/drivers/virtio_uml.c
>> @@ -72,7 +72,7 @@ struct virtio_uml_vq_info {
>> bool suspended;
>> };
>>
>> -extern unsigned long long physmem_size, highmem;
>> +extern unsigned long long physmem_size;
>>
>> #define vu_err(vu_dev, ...) dev_err(&(vu_dev)->pdev->dev,
>> ##__VA_ARGS__)
>>
>> @@ -673,13 +673,6 @@ static int vhost_user_set_mem_table(struct
>> virtio_uml_device *vu_dev)
>>
>> if (rc < 0)
>> return rc;
>> - if (highmem) {
>> - msg.payload.mem_regions.num++;
>> - rc = vhost_user_init_mem_region(__pa(end_iomem),
>> highmem,
>> - &fds[1],
>> &msg.payload.mem_regions.regions[1]);
>> - if (rc < 0)
>> - return rc;
>> - }
>>
>> return vhost_user_send(vu_dev, false, &msg, fds,
>> msg.payload.mem_regions.num);
>> diff --git a/arch/um/include/shared/as-layout.h
>> b/arch/um/include/shared/as-layout.h
>> index 06292fca5a4d..61965a06c18a 100644
>> --- a/arch/um/include/shared/as-layout.h
>> +++ b/arch/um/include/shared/as-layout.h
>> @@ -41,7 +41,6 @@ extern unsigned long uml_physmem;
>> extern unsigned long uml_reserved;
>> extern unsigned long end_vm;
>> extern unsigned long start_vm;
>> -extern unsigned long long highmem;
>>
>> extern unsigned long brk_start;
>>
>> diff --git a/arch/um/include/shared/mem_user.h
>> b/arch/um/include/shared/mem_user.h
>> index 11a723a58545..adfa08062f88 100644
>> --- a/arch/um/include/shared/mem_user.h
>> +++ b/arch/um/include/shared/mem_user.h
>> @@ -47,10 +47,9 @@ extern int iomem_size;
>> #define ROUND_4M(n) ((((unsigned long) (n)) + (1 << 22)) & ~((1 <<
>> 22) - 1))
>>
>> extern unsigned long find_iomem(char *driver, unsigned long
>> *len_out);
>> -extern void mem_total_pages(unsigned long physmem, unsigned long
>> iomem,
>> - unsigned long highmem);
>> +extern void mem_total_pages(unsigned long physmem, unsigned long
>> iomem);
>> extern void setup_physmem(unsigned long start, unsigned long usable,
>> - unsigned long len, unsigned long long
>> highmem);
>> + unsigned long len);
>> extern void map_memory(unsigned long virt, unsigned long phys,
>> unsigned long len, int r, int w, int x);
>>
>> diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
>> index a5b4fe2ad931..5026668dc054 100644
>> --- a/arch/um/kernel/mem.c
>> +++ b/arch/um/kernel/mem.c
>> @@ -6,7 +6,6 @@
>> #include <linux/stddef.h>
>> #include <linux/module.h>
>> #include <linux/memblock.h>
>> -#include <linux/highmem.h>
>> #include <linux/mm.h>
>> #include <linux/swap.h>
>> #include <linux/slab.h>
>> @@ -51,8 +50,6 @@ EXPORT_SYMBOL(empty_zero_page);
>> pgd_t swapper_pg_dir[PTRS_PER_PGD];
>>
>> /* Initialized at boot time, and readonly after that */
>> -unsigned long long highmem;
>> -EXPORT_SYMBOL(highmem);
>> int kmalloc_ok = 0;
>>
>> /* Used during early boot */
>> diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
>> index fb2adfb49945..cc5238c1bf1e 100644
>> --- a/arch/um/kernel/physmem.c
>> +++ b/arch/um/kernel/physmem.c
>> @@ -24,17 +24,14 @@ EXPORT_SYMBOL(high_physmem);
>>
>> extern unsigned long long physmem_size;
>>
>> -void __init mem_total_pages(unsigned long physmem, unsigned long
>> iomem,
>> - unsigned long highmem)
>> +void __init mem_total_pages(unsigned long physmem, unsigned long
>> iomem)
>> {
>> - unsigned long phys_pages, highmem_pages;
>> - unsigned long iomem_pages, total_pages;
>> + unsigned long phys_pages, iomem_pages, total_pages;
>>
>> - phys_pages = physmem >> PAGE_SHIFT;
>> - iomem_pages = iomem >> PAGE_SHIFT;
>> - highmem_pages = highmem >> PAGE_SHIFT;
>> + phys_pages = physmem >> PAGE_SHIFT;
>> + iomem_pages = iomem >> PAGE_SHIFT;
>>
>> - total_pages = phys_pages + iomem_pages + highmem_pages;
>> + total_pages = phys_pages + iomem_pages;
>>
>> max_mapnr = total_pages;
>> }
>> @@ -64,13 +61,12 @@ void map_memory(unsigned long virt, unsigned long
>> phys, unsigned long len,
>> * @reserve_end: end address of the physical kernel memory.
>> * @len: Length of total physical memory that should be
>> mapped/made
>> * available, in bytes.
>> - * @highmem: Number of highmem bytes that should be mapped/made
>> available.
>> *
>> - * Creates an unlinked temporary file of size (len + highmem) and
>> memory maps
>> + * Creates an unlinked temporary file of size (len) and memory maps
>> * it on the last executable image address (uml_reserved).
>> *
>> * The offset is needed as the length of the total physical memory
>> - * (len + highmem) includes the size of the memory used be the
>> executable image,
>> + * (len) includes the size of the memory used be the executable
>> image,
>> * but the mapped-to address is the last address of the executable
>> image
>> * (uml_reserved == end address of executable image).
>> *
>> @@ -78,19 +74,19 @@ void map_memory(unsigned long virt, unsigned long
>> phys, unsigned long len,
>> * of all user space processes/kernel tasks.
>> */
>> void __init setup_physmem(unsigned long start, unsigned long
>> reserve_end,
>> - unsigned long len, unsigned long long
>> highmem)
>> + unsigned long len)
>> {
>> unsigned long reserve = reserve_end - start;
>> long map_size = len - reserve;
>> int err;
>>
>> - if(map_size <= 0) {
>> + if (map_size <= 0) {
>> os_warn("Too few physical memory! Needed=%lu,
>> given=%lu\n",
>> reserve, len);
>> exit(1);
>> }
>>
>> - physmem_fd = create_mem_file(len + highmem);
>> + physmem_fd = create_mem_file(len);
>>
>> err = os_map_memory((void *) reserve_end, physmem_fd,
>> reserve,
>> map_size, 1, 1, 1);
>> @@ -109,7 +105,7 @@ void __init setup_physmem(unsigned long start,
>> unsigned long reserve_end,
>> os_write_file(physmem_fd, __syscall_stub_start, PAGE_SIZE);
>> os_fsync_file(physmem_fd);
>>
>> - memblock_add(__pa(start), len + highmem);
>> + memblock_add(__pa(start), len);
>> memblock_reserve(__pa(start), reserve);
>>
>> min_low_pfn = PFN_UP(__pa(reserve_end));
>> @@ -137,10 +133,6 @@ int phys_mapping(unsigned long phys, unsigned
>> long long *offset_out)
>> region = region->next;
>> }
>> }
>> - else if (phys < __pa(end_iomem) + highmem) {
>> - fd = physmem_fd;
>> - *offset_out = phys - iomem_size;
>> - }
>>
>> return fd;
>> }
>> diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
>> index 8e594cda6d77..8f86aa468b50 100644
>> --- a/arch/um/kernel/um_arch.c
>> +++ b/arch/um/kernel/um_arch.c
>> @@ -366,18 +366,15 @@ int __init linux_main(int argc, char **argv)
>>
>> setup_machinename(init_utsname()->machine);
>>
>> - highmem = 0;
>> + physmem_size = (physmem_size + PAGE_SIZE - 1) & PAGE_MASK;
>> iomem_size = (iomem_size + PAGE_SIZE - 1) & PAGE_MASK;
>> +
>> max_physmem = TASK_SIZE - uml_physmem - iomem_size -
>> MIN_VMALLOC;
>>
>> - /*
>> - * Zones have to begin on a 1 << MAX_PAGE_ORDER page
>> boundary,
>> - * so this makes sure that's true for highmem
>> - */
>> - max_physmem &= ~((1 << (PAGE_SHIFT + MAX_PAGE_ORDER)) - 1);
>> if (physmem_size + iomem_size > max_physmem) {
>> - highmem = physmem_size + iomem_size - max_physmem;
>> - physmem_size -= highmem;
>> + physmem_size = max_physmem - iomem_size;
>> + os_info("Physical memory size shrunk to %llu
>> bytes\n",
>> + physmem_size);
>> }
>>
>> high_physmem = uml_physmem + physmem_size;
>> @@ -413,8 +410,8 @@ void __init setup_arch(char **cmdline_p)
>> u8 rng_seed[32];
>>
>> stack_protections((unsigned long) &init_thread_info);
>> - setup_physmem(uml_physmem, uml_reserved, physmem_size,
>> highmem);
>> - mem_total_pages(physmem_size, iomem_size, highmem);
>> + setup_physmem(uml_physmem, uml_reserved, physmem_size);
>> + mem_total_pages(physmem_size, iomem_size);
>> uml_dtb_init();
>> read_initrd();
>>
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