Re: [Qemu-devel] [PATCH 5/8] exec: Drop incorrect & dead S390 code in qemu_ram_remap()

[Markus Armbruster]

Paolo Bonzini <address@hidden> writes:

> Il 19/06/2013 13:44, Markus Armbruster ha scritto:
>> Old S390 KVM wants guest RAM mapped in a peculiar way.  Commit 6b02494
>> implemented that.
>> 
>> When qemu_ram_remap() got added in commit cd19cfa, its code carefully
>> mimicked the allocation code: peculiar way if defined(TARGET_S390X) &&
>> defined(CONFIG_KVM), else normal way.
>> 
>> For new S390 KVM, we actually want the normal way.  Commit fdec991
>> changed qemu_ram_alloc_from_ptr() accordingly, but forgot to update
>> qemu_ram_remap().  If qemu_ram_alloc_from_ptr() maps RAM the normal
>> way, but qemu_ram_remap() remaps it the peculiar way, remapping
>> changes protection and flags, which it shouldn't.
>> 
>> Fortunately, this can't happen, as we never remap on S390.
>> 
>> Replace the incorrect code with an assertion.
>> 
>> Thanks to Christian Borntraeger for help with assessing the bug's
>> (non-)impact.
>> 
>> Signed-off-by: Markus Armbruster <address@hidden>
>> ---
>>  exec.c | 13 +++++++------
>>  1 file changed, 7 insertions(+), 6 deletions(-)
>> 
>> diff --git a/exec.c b/exec.c
>> index c45eb33..a0f18fe 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -1229,15 +1229,16 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t 
>> length)
>>                      area = mmap(vaddr, length, PROT_READ | PROT_WRITE,
>>                                  flags, block->fd, offset);
>>                  } else {
>> -#if defined(TARGET_S390X) && defined(CONFIG_KVM)
>> -                    flags |= MAP_SHARED | MAP_ANONYMOUS;
>> -                    area = mmap(vaddr, length, 
>> PROT_EXEC|PROT_READ|PROT_WRITE,
>> -                                flags, -1, 0);
>> -#else
>> +                    /*
>> +                     * Remap needs to match alloc.  Accelerators that
>> +                     * set phys_mem_alloc never remap.  If they did,
>> +                     * we'd need a remap hook here.
>> +                     */
>> +                    assert(!phys_mem_alloc);
>
> Probably "assert(phys_mem_alloc == qemu_anon_ram_alloc)"?

Of course.  Will fix.

> Otherwise all looks fine.

Thanks!