From: Pierre Morel <pmorel@linux.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: thuth@redhat.com, Matthew Rosato <mjrosato@linux.ibm.com>,
david@redhat.com, richard.henderson@linaro.org,
qemu-devel@nongnu.org, pasic@linux.ibm.com,
borntraeger@de.ibm.com, qemu-s390x@nongnu.org
Subject: Re: [PATCH v2 2/2] s390x/pci: Fix memory_region_access_valid call
Date: Fri, 18 Dec 2020 15:32:08 +0100 [thread overview]
Message-ID: <2c5a2ccb-dbe1-f355-3980-462be1d93942@linux.ibm.com> (raw)
In-Reply-To: <20201218120440.36b56e80.cohuck@redhat.com>
On 12/18/20 12:04 PM, Cornelia Huck wrote:
> On Fri, 18 Dec 2020 10:37:38 +0100
> Pierre Morel <pmorel@linux.ibm.com> wrote:
>
>> On 12/17/20 11:16 PM, Matthew Rosato wrote:
>>> In pcistb_service_handler, a call is made to validate that the memory
>>> region can be accessed. However, the call is made using the entire length
>>> of the pcistb operation, which can be larger than the allowed memory
>>> access size (8). Since we already know that the provided buffer is a
>>> multiple of 8, fix the call to memory_region_access_valid to iterate
>>> over the memory region in the same way as the subsequent call to
>>> memory_region_dispatch_write.
>>>
>>> Fixes: 863f6f52b7 ("s390: implement pci instructions")
>>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>>> ---
>>> hw/s390x/s390-pci-inst.c | 10 ++++++----
>>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
>>> index e230293..76b08a3 100644
>>> --- a/hw/s390x/s390-pci-inst.c
>>> +++ b/hw/s390x/s390-pci-inst.c
>>> @@ -821,10 +821,12 @@ int pcistb_service_call(S390CPU *cpu, uint8_t r1, uint8_t r3, uint64_t gaddr,
>>> mr = s390_get_subregion(mr, offset, len);
>>> offset -= mr->addr;
>>>
>>> - if (!memory_region_access_valid(mr, offset, len, true,
>>> - MEMTXATTRS_UNSPECIFIED)) {
>>> - s390_program_interrupt(env, PGM_OPERAND, ra);
>>> - return 0;
>>> + for (i = 0; i < len; i += 8) {
>>> + if (!memory_region_access_valid(mr, offset + i, 8, true,
>>> + MEMTXATTRS_UNSPECIFIED)) {
>>> + s390_program_interrupt(env, PGM_OPERAND, ra);
>>> + return 0;
>>> + }
>>> }
>>>
>>> if (s390_cpu_virt_mem_read(cpu, gaddr, ar, buffer, len)) {
>>>
>>
>> wouldn't it be made automatically by defining the io_region
>> max_access_size when reading the bars in clp_service_call?
>>
>
> But that's already what is happening, isn't it? The access check is
> done for a size that is potentially too large, while the actual access
> will happen in chunks of 8? I think that this patch is correct.
>
Sorry I was too rapid and half wrong in my writing I was also not
specific enough.
In MemoryRegionOps we have a field valid with a callback accepts().
I was wondering if doing the check in the accept() callback which is
called by the memory_region_access_valid() function and then using
max_access_size would not be cleaner.
Note that it does not change a lot but only where the check is done.
--
Pierre Morel
IBM Lab Boeblingen
next prev parent reply other threads:[~2020-12-18 14:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 22:16 [PATCH v2 0/2] s390x/pci: some pcistb fixes Matthew Rosato
2020-12-17 22:16 ` [PATCH v2 1/2] s390x/pci: fix pcistb length Matthew Rosato
2020-12-18 9:22 ` Christian Borntraeger
2020-12-17 22:16 ` [PATCH v2 2/2] s390x/pci: Fix memory_region_access_valid call Matthew Rosato
2020-12-18 6:10 ` Thomas Huth
2020-12-18 9:37 ` Pierre Morel
2020-12-18 11:04 ` Cornelia Huck
2020-12-18 14:32 ` Pierre Morel [this message]
2020-12-18 15:32 ` Cornelia Huck
2020-12-18 16:40 ` Pierre Morel
2020-12-18 16:51 ` Cornelia Huck
2020-12-18 17:05 ` Pierre Morel
2020-12-21 8:50 ` Pierre Morel
2020-12-21 10:21 ` Cornelia Huck
2020-12-21 12:22 ` [PATCH v2 0/2] s390x/pci: some pcistb fixes Cornelia Huck
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