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Re: [Qemu-devel] [PATCH v3 7/7] memory-device: rewrite address assignmen
From: |
David Hildenbrand |
Subject: |
Re: [Qemu-devel] [PATCH v3 7/7] memory-device: rewrite address assignment using ranges |
Date: |
Tue, 13 Nov 2018 13:41:07 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 |
On 13.11.18 13:26, Igor Mammedov wrote:
> On Tue, 23 Oct 2018 17:23:06 +0200
> David Hildenbrand <address@hidden> wrote:
>
>> Let's rewrite it properly using ranges. This fixes certain overflows that
>> are right now possible. E.g.
>>
>> qemu-system-x86_64 -m 4G,slots=20,maxmem=40G -M pc \
>> -object memory-backend-file,id=mem1,share,mem-path=/dev/zero,size=2G
>> -device pc-dimm,memdev=mem1,id=dimm1,addr=-0x40000000
>>
>> Now properly reports an error instead of succeeding.
> s/error/error out/
Thanks, fixed.
>
>>
>> "can't add memory device [0xffffffffc0000000:0x80000000], range overflow"
>>
>> Signed-off-by: David Hildenbrand <address@hidden>
>> ---
>> hw/mem/memory-device.c | 53 ++++++++++++++++++++++++------------------
>> 1 file changed, 30 insertions(+), 23 deletions(-)
>>
>> diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
>> index 8be63c8032..2fb6fc2145 100644
>> --- a/hw/mem/memory-device.c
>> +++ b/hw/mem/memory-device.c
>> @@ -100,9 +100,8 @@ static uint64_t memory_device_get_free_addr(MachineState
>> *ms,
>> uint64_t align, uint64_t size,
>> Error **errp)
>> {
>> - uint64_t address_space_start, address_space_end;
>> GSList *list = NULL, *item;
>> - uint64_t new_addr = 0;
>> + Range as, new = range_empty;
>>
>> if (!ms->device_memory) {
>> error_setg(errp, "memory devices (e.g. for memory hotplug) are not "
>> @@ -115,13 +114,11 @@ static uint64_t
>> memory_device_get_free_addr(MachineState *ms,
>> "enabled, please specify the maxmem option");
>> return 0;
>> }
>> - address_space_start = ms->device_memory->base;
>> - address_space_end = address_space_start +
>> - memory_region_size(&ms->device_memory->mr);
>> - g_assert(address_space_end >= address_space_start);
>> + range_init_nofail(&as, ms->device_memory->base,
>> + memory_region_size(&ms->device_memory->mr));
>>
>> - /* address_space_start indicates the maximum alignment we expect */
>> - if (!QEMU_IS_ALIGNED(address_space_start, align)) {
>> + /* start of address space indicates the maximum alignment we expect */
>> + if (!QEMU_IS_ALIGNED(range_lob(&as), align)) {
>> error_setg(errp, "the alignment (0x%" PRIx64 ") is not supported",
>> align);
>> return 0;
>> @@ -145,20 +142,24 @@ static uint64_t
>> memory_device_get_free_addr(MachineState *ms,
>> }
>>
>> if (hint) {
>> - new_addr = *hint;
>> - if (new_addr < address_space_start) {
>> + if (range_init(&new, *hint, size)) {
>> error_setg(errp, "can't add memory device [0x%" PRIx64 ":0x%"
>> PRIx64
>> - "] before 0x%" PRIx64, new_addr, size,
>> - address_space_start);
>> + "], range overflow", *hint, size);
>> return 0;
>> - } else if ((new_addr + size) > address_space_end) {
>> + }
>> + if (!range_contains_range(&as, &new)) {
>> error_setg(errp, "can't add memory device [0x%" PRIx64 ":0x%"
>> PRIx64
>> - "] beyond 0x%" PRIx64, new_addr, size,
>> - address_space_end);
>> + "], usable range for memory devices [0x%" PRIx64
>> ":0x%"
>> + PRIx64 "]", range_lob(&new), range_size(&new),
>> + range_lob(&as), range_size(&as));
>> return 0;
>> }
>> } else {
>> - new_addr = address_space_start;
>> + if (range_init(&new, range_lob(&as), size)) {
>> + error_setg(errp, "can't add memory device [0x%" PRIx64 ":0x%"
>> PRIx64
>> + "], range overflow", *hint, size);
> maybe replace "range overflow" with "too big" or something else more user
> friendly
I guess I'll use the same error message for these two cases
"can't add memory device [...], usable range for memory devices [...]"
That will include the "range overflow" scenario when a hint was given.
>
>> + return 0;
>> + }
>> }
>>
>> /* find address range that will fit new memory device */
>> @@ -166,30 +167,36 @@ static uint64_t
>> memory_device_get_free_addr(MachineState *ms,
>> for (item = list; item; item = g_slist_next(item)) {
>> const MemoryDeviceState *md = item->data;
>> const MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(OBJECT(md));
>> - uint64_t md_size, md_addr;
>> + uint64_t next_addr;
>> + Range tmp;
>>
>> - md_addr = mdc->get_addr(md);
>> - md_size = memory_device_get_region_size(md, &error_abort);
>> + range_init_nofail(&tmp, mdc->get_addr(md),
>> + memory_device_get_region_size(md, &error_abort));
>>
>> - if (ranges_overlap(md_addr, md_size, new_addr, size)) {
>> + if (range_overlaps_range(&tmp, &new)) {
>> if (hint) {
>> const DeviceState *d = DEVICE(md);
>> error_setg(errp, "address range conflicts with memory
>> device"
>> " id='%s'", d->id ? d->id : "(unnamed)");
>> goto out;
>> }
>> - new_addr = QEMU_ALIGN_UP(md_addr + md_size, align);
>> +
>> + next_addr = QEMU_ALIGN_UP(range_upb(&tmp) + 1, align);
> ^^^^^^^^^^^^^^^^^^^
> this theoretically could overflow and already past 'as' check so it would
> return an invalid address without erroring out.
>
> But in practice we don't have memory device container ending right on 64bit
> limit, so it's not really an issue.
I'll add a simple check for "!next_addr".
>
>
>> + if (range_init(&new, next_addr, range_size(&new))) {
>> + range_make_empty(&new);
>> + break;
>> + }
>> }
>> }
>>
>> - if (new_addr + size > address_space_end) {
>> + if (!range_contains_range(&as, &new)) {
>> error_setg(errp, "could not find position in guest address space
>> for "
>> "memory device - memory fragmented due to alignments");
>> goto out;
>> }
>> out:
>> g_slist_free(list);
>> - return new_addr;
>> + return range_lob(&new);
>> }
>>
>> MemoryDeviceInfoList *qmp_memory_device_list(void)
>
> beside minor notes patch looks good
>
Thanks!
--
Thanks,
David / dhildenb