On 09.07.20 12:37, Cornelia Huck wrote:
> On Wed, 8 Jul 2020 20:51:32 +0200
> David Hildenbrand <da...@redhat.com> wrote:
>
>> Let's implement the "storage configuration" part of diag260. This diag
>> is found under z/VM, to indicate usable chunks of memory tot he guest OS.
>> As I don't have access to documentation, I have no clue what the actual
>> error cases are, and which other stuff we could eventually query using this
>> interface. Somebody with access to documentation should fix this. This
>> implementation seems to work with Linux guests just fine.
>>
>> The Linux kernel supports diag260 to query the available memory since
>> v4.20. Older kernels / kvm-unit-tests will later fail to run in such a VM
>> (with maxmem being defined and bigger than the memory size, e.g., "-m
>> 2G,maxmem=4G"), just as if support for SCLP storage information is not
>> implemented. They will fail to detect the actual initial memory size.
>>
>> This interface allows us to expose the maximum ramsize via sclp
>> and the initial ramsize via diag260 - without having to mess with the
>> memory increment size and having to align the initial memory size to it.
>>
>> This is a preparation for memory device support. We'll unlock the
>> implementation with a new QEMU machine that supports memory devices.
>>
>> Signed-off-by: David Hildenbrand <da...@redhat.com>
>> ---
>> target/s390x/diag.c | 57 ++++++++++++++++++++++++++++++++++++++
>> target/s390x/internal.h | 2 ++
>> target/s390x/kvm.c | 11 ++++++++
>> target/s390x/misc_helper.c | 6 ++++
>> target/s390x/translate.c | 4 +++
>> 5 files changed, 80 insertions(+)
>>
>> diff --git a/target/s390x/diag.c b/target/s390x/diag.c
>> index 1a48429564..c3b1e24b2c 100644
>> --- a/target/s390x/diag.c
>> +++ b/target/s390x/diag.c
>> @@ -23,6 +23,63 @@
>> #include "hw/s390x/pv.h"
>> #include "kvm_s390x.h"
>>
>> +void handle_diag_260(CPUS390XState *env, uint64_t r1, uint64_t r3,
>> uintptr_t ra)
>> +{
>> + MachineState *ms = MACHINE(qdev_get_machine());
>> + const ram_addr_t initial_ram_size = ms->ram_size;
>> + const uint64_t subcode = env->regs[r3];
>> + S390CPU *cpu = env_archcpu(env);
>> + ram_addr_t addr, length;
>> + uint64_t tmp;
>> +
>> + /* TODO: Unlock with new QEMU machine. */
>> + if (false) {
>> + s390_program_interrupt(env, PGM_OPERATION, ra);
>> + return;
>> + }
>> +
>> + /*
>> + * There also seems to be subcode "0xc", which stores the size of the
>> + * first chunk and the total size to r1/r2. It's only used by very old
>> + * Linux, so don't implement it.
>
> FWIW,
> https://www-01.ibm.com/servers/resourcelink/svc0302a.nsf/pages/zVMV7R1sc246272/$file/hcpb4_v7r1.pdf
> seems to list the available subcodes. Anything but 0xc and 0x10 is for
> 24/31 bit only, so we can safely ignore them. Not sure what we want to
> do with 0xc: it is supposed to "Return the highest addressable byte of
> virtual storage in the host-primary address space, including named
> saved systems and saved segments", so returning the end of the address
> space should be easy enough, but not very useful.
>
>> + */
>> + if ((r1 & 1) || subcode != 0x10) {
>> + s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>> + return;
>> + }
>> + addr = env->regs[r1];
>> + length = env->regs[r1 + 1];
>> +
>> + /* FIXME: Somebody with documentation should fix this. */
>
> Doc mentioned above says for specification exception:
>
> "For subcode X'10':
> • Rx is not an even-numbered register.
> • The address contained in Rx is not on a quadword boundary.
> • The length contained in Rx+1 is not a positive multiple of 16."
>
>> + if (!QEMU_IS_ALIGNED(addr, 16) || !QEMU_IS_ALIGNED(length, 16)) {
>> + s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>> + return;
>> + }
>> +
>> + /* FIXME: Somebody with documentation should fix this. */
>> + if (!length) {
>
> Probably specification exception as well?
>
>> + setcc(cpu, 3);
>> + return;
>> + }
>> +
>> + /* FIXME: Somebody with documentation should fix this. */
>
> For access exception:
>
> "For subcode X'10', an error occurred trying to store the extent
> information into the guest's output area."
>
>> + if (!address_space_access_valid(&address_space_memory, addr, length,
>> true,
>> + MEMTXATTRS_UNSPECIFIED)) {
>> + s390_program_interrupt(env, PGM_ADDRESSING, ra);
>> + return;
>> + }
>> +
>> + /* Indicate our initial memory ([0 .. ram_size - 1]) */
>> + tmp = cpu_to_be64(0);
>> + cpu_physical_memory_write(addr, &tmp, sizeof(tmp));
>> + tmp = cpu_to_be64(initial_ram_size - 1);
>> + cpu_physical_memory_write(addr + sizeof(tmp), &tmp, sizeof(tmp));
>> +
>> + /* Exactly one entry was stored. */
>> + env->regs[r3] = 1;
>> + setcc(cpu, 0);
>> +}
>> +
>> int handle_diag_288(CPUS390XState *env, uint64_t r1, uint64_t r3)
>> {
>> uint64_t func = env->regs[r1];
>
> (...)
>
>> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
>> index 58dbc023eb..d7274eb320 100644
>> --- a/target/s390x/misc_helper.c
>> +++ b/target/s390x/misc_helper.c
>> @@ -116,6 +116,12 @@ void HELPER(diag)(CPUS390XState *env, uint32_t r1,
>> uint32_t r3, uint32_t num)
>> uint64_t r;
>>
>> switch (num) {
>> + case 0x260:
>> + qemu_mutex_lock_iothread();
>> + handle_diag_260(env, r1, r3, GETPC());
>> + qemu_mutex_unlock_iothread();
>> + r = 0;
>> + break;
>> case 0x500:
>> /* KVM hypercall */
>> qemu_mutex_lock_iothread();
>
> Looking at the doc referenced above, it seems that we treat every diag
> call as privileged under tcg; but it seems that 0x44 isn't? (Unrelated
> to your patch; maybe I'm misreading.)
That's also a BUG in kvm then?
int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
{
...
if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
...
}
--
Thanks,
David / dhildenb
