Re: [PATCH v1 07/12] s390x/mmu_helper: move address validation into mmu_translate*()

[David Hildenbrand <david@redhat.com>]

On 06.08.21 10:22, Thomas Huth wrote:
> On 06/08/2021 10.20, David Hildenbrand wrote:
>> On 06.08.21 10:18, Thomas Huth wrote:
>>> On 05/08/2021 17.27, David Hildenbrand wrote:
>>>> Let's move address validation into mmu_translate() and
>>>> mmu_translate_real(). This allows for checking whether an absolute
>>>> address is valid before looking up the storage key. We can now get rid of
>>>> the ram_size check.
>>>>
>>>> Interestingly, we're already handling LOAD REAL ADDRESS wrong, because
>>>> a) We're not supposed to touch storage keys
>>>> b) We're not supposed to convert to an absolute address
>>>>
>>>> Let's use a fake, negative MMUAccessType to teach mmu_translate() to
>>>> fix that handling and to not perform address validation.
>>>>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>> ---
>>>>     target/s390x/mmu_helper.c      | 36 ++++++++++++++++++++--------------
>>>>     target/s390x/tcg/excp_helper.c | 13 ------------
>>>>     target/s390x/tcg/mem_helper.c  |  2 +-
>>>>     3 files changed, 22 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/target/s390x/mmu_helper.c b/target/s390x/mmu_helper.c
>>>> index ca25dadb5b..36ab4e9c81 100644
>>>> --- a/target/s390x/mmu_helper.c
>>>> +++ b/target/s390x/mmu_helper.c
>>>> @@ -301,14 +301,13 @@ static void mmu_handle_skey(target_ulong addr, int
>>>> rw, int *flags)
>>>>     {
>>>>         static S390SKeysClass *skeyclass;
>>>>         static S390SKeysState *ss;
>>>> -    MachineState *ms = MACHINE(qdev_get_machine());
>>>>         uint8_t key;
>>>>         int rc;
>>>> -    if (unlikely(addr >= ms->ram_size)) {
>>>> -        return;
>>>> -    }
>>>> -
>>>> +    /*
>>>> +     * We excpect to be called with an absolute address that has already
>>>> been
>>>> +     * validated, such that we can reliably use it to lookup the storage
>>>> key.
>>>> +     */
>>>>         if (unlikely(!ss)) {
>>>>             ss = s390_get_skeys_device();
>>>>             skeyclass = S390_SKEYS_GET_CLASS(ss);
>>>> @@ -370,7 +369,7 @@ static void mmu_handle_skey(target_ulong addr, int
>>>> rw, int *flags)
>>>>     /**
>>>>      * Translate a virtual (logical) address into a physical (absolute)
>>>> address.
>>>>      * @param vaddr  the virtual address
>>>> - * @param rw     0 = read, 1 = write, 2 = code fetch
>>>> + * @param rw     0 = read, 1 = write, 2 = code fetch, < 0 = load real
>>>> address
>>>>      * @param asc    address space control (one of the PSW_ASC_* modes)
>>>>      * @param raddr  the translated address is stored to this pointer
>>>>      * @param flags  the PAGE_READ/WRITE/EXEC flags are stored to this
>>>> pointer
>>>> @@ -449,10 +448,17 @@ int mmu_translate(CPUS390XState *env, target_ulong
>>>> vaddr, int rw, uint64_t asc,
>>>>         }
>>>>     nodat:
>>>> -    /* Convert real address -> absolute address */
>>>> -    *raddr = mmu_real2abs(env, *raddr);
>>>> +    if (rw >= 0) {
>>>> +        /* Convert real address -> absolute address */
>>>> +        *raddr = mmu_real2abs(env, *raddr);
>>>> -    mmu_handle_skey(*raddr, rw, flags);
>>>> +        if (!mmu_absolute_addr_valid(*raddr, rw == MMU_DATA_STORE)) {
>>>> +            *tec = 0; /* unused */
>>>> +            return PGM_ADDRESSING;
>>>> +        }
>>>> +
>>>> +        mmu_handle_skey(*raddr, rw, flags);
>>>> +    }
>>>>         return 0;
>>>>     }
>>>> @@ -473,12 +479,6 @@ static int translate_pages(S390CPU *cpu, vaddr addr,
>>>> int nr_pages,
>>>>             if (ret) {
>>>>                 return ret;
>>>>             }
>>>> -        if (!address_space_access_valid(&address_space_memory, pages[i],
>>>> -                                        TARGET_PAGE_SIZE, is_write,
>>>> -                                        MEMTXATTRS_UNSPECIFIED)) {
>>>> -            *tec = 0; /* unused */
>>>> -            return PGM_ADDRESSING;
>>>> -        }
>>>>             addr += TARGET_PAGE_SIZE;
>>>>         }
>>>> @@ -588,6 +588,12 @@ int mmu_translate_real(CPUS390XState *env,
>>>> target_ulong raddr, int rw,
>>>>         *addr = mmu_real2abs(env, raddr & TARGET_PAGE_MASK);
>>>> +    if (!mmu_absolute_addr_valid(*addr, rw == MMU_DATA_STORE)) {
>>>> +        /* unused */
>>>> +        *tec = 0;
>>>> +        return PGM_ADDRESSING;
>>>> +    }
>>>> +
>>>>         mmu_handle_skey(*addr, rw, flags);
>>>>         return 0;
>>>>     }
>>>> diff --git a/target/s390x/tcg/excp_helper.c b/target/s390x/tcg/excp_helper.c
>>>> index a61917d04f..3d6662a53c 100644
>>>> --- a/target/s390x/tcg/excp_helper.c
>>>> +++ b/target/s390x/tcg/excp_helper.c
>>>> @@ -150,19 +150,6 @@ bool s390_cpu_tlb_fill(CPUState *cs, vaddr address,
>>>> int size,
>>>>             g_assert_not_reached();
>>>>         }
>>>> -    /* check out of RAM access */
>>>> -    if (!excp &&
>>>> -        !address_space_access_valid(&address_space_memory, raddr,
>>>> -                                    TARGET_PAGE_SIZE, access_type,
>>>> -                                    MEMTXATTRS_UNSPECIFIED)) {
>>>> -        MachineState *ms = MACHINE(qdev_get_machine());
>>>> -        qemu_log_mask(CPU_LOG_MMU,
>>>> -                      "%s: raddr %" PRIx64 " > ram_size %" PRIx64 "\n",
>>>> -                      __func__, (uint64_t)raddr, (uint64_t)ms->ram_size);
>>>> -        excp = PGM_ADDRESSING;
>>>> -        tec = 0; /* unused */
>>>> -    }
>>>> -
>>>>         env->tlb_fill_exc = excp;
>>>>         env->tlb_fill_tec = tec;
>>>> diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
>>>> index a84795cfa3..9c1b9c7d06 100644
>>>> --- a/target/s390x/tcg/mem_helper.c
>>>> +++ b/target/s390x/tcg/mem_helper.c
>>>> @@ -2456,7 +2456,7 @@ uint64_t HELPER(lra)(CPUS390XState *env, uint64_t
>>>> addr)
>>>>             tcg_s390_program_interrupt(env, PGM_SPECIAL_OP, GETPC());
>>>>         }
>>>> -    exc = mmu_translate(env, addr, 0, asc, &ret, &flags, &tec);
>>>> +    exc = mmu_translate(env, addr, -1, asc, &ret, &flags, &tec);
>>>
>>> Do we maybe want a #define for this -1 instead? OTOH, you've added a proper
>>> comment to the function description, so that should be ok, too.
>>
>> Ideally, I'd have used a completely new MMU_* type. But affecting all users
>> in QEMU for one special case and having to handle it consequently
>> accordingly all over the place feels wrong.
>>
>> Where would you put the define?
> 
> I agree that this should not go into the common header ... so maybe into
> s390x-internal.h ?

Maybe calling it MMU_S390_LRA ?


-- 
Thanks,

David / dhildenb