On 5/2/22 10:25, Thomas Huth wrote:
> TPROT allows to specify an access key that should be used for checking
> with the storage key of the destination page, to see whether an access
> is allowed or not. Honor this storage key checking now in the emulated
> TPROT instruction, too.
>
> Since we need the absolute address of the page (for getting the storage
> key), we are now also calling mmu_translate() directly instead of
> going via s390_cpu_virt_mem_check_write/read() - since we're only
> interested in one page, and since mmu_translate() does not try to inject
> excetions directly (it reports them via the return code instead), this
> is likely the better function to use in TPROT anyway.
>
> Signed-off-by: Thomas Huth
> ---
> This fixes the new TPROT-related storage key checks in this new
> kvm-unit-tests patch:
> https://lore.kernel.org/kvm/20220425161731.1575742-1-s...@linux.ibm.com/
Thanks for having a go at this.
The key checking logic looks good to me; the expressions get a bit unwieldy,
but that is a style thing.
However, I'm wondering whether it would be better to mirror what the kernel
is doing and address the
* TODO: key-controlled protection. Only CPU accesses make use of the
* PSW key. CSS accesses are different - we have to pass in the key.
in mmu_handle_skey, then tprot emulation would just relay the result of trying
the translation with store or fetch, passing in the key.
>
> target/s390x/cpu.h| 1 +
> target/s390x/tcg/mem_helper.c | 61 ---
> 2 files changed, 50 insertions(+), 12 deletions(-)
>
> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> index 7d6d01325b..348950239f 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -328,6 +328,7 @@ extern const VMStateDescription vmstate_s390_cpu;
> /* Control register 0 bits */
> #define CR0_LOWPROT 0x1000ULL
> #define CR0_SECONDARY 0x0400ULL
> +#define CR0_STOR_PROT_OVERRIDE 0x0100ULL
> #define CR0_EDAT0x0080ULL
> #define CR0_AFP 0x0004ULL
> #define CR0_VECTOR 0x0002ULL
> diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
> index fc52aa128b..1e0309bbe8 100644
> --- a/target/s390x/tcg/mem_helper.c
> +++ b/target/s390x/tcg/mem_helper.c
> @@ -2141,43 +2141,80 @@ uint32_t HELPER(testblock)(CPUS390XState *env,
> uint64_t real_addr)
> return 0;
> }
>
[...]
> +
> uint32_t HELPER(tprot)(CPUS390XState *env, uint64_t a1, uint64_t a2)
> {
> S390CPU *cpu = env_archcpu(env);
> -CPUState *cs = env_cpu(env);
> +const int tp_acc = (a2 & SK_ACC_MASK) >> 4;
> +uint8_t skey;
> +int acc, pgm_code, pflags;
> +target_ulong abs_addr;
> +uint64_t asc = cpu->env.psw.mask & PSW_MASK_ASC;
> +uint64_t tec;
>
> /*
> * TODO: we currently don't handle all access protection types
> - * (including access-list and key-controlled) as well as AR mode.
> + * (including access-list) as well as AR mode.
> */
> -if (!s390_cpu_virt_mem_check_write(cpu, a1, 0, 1)) {
> -/* Fetching permitted; storing permitted */
> +pgm_code = mmu_translate(env, a1, true, asc, _addr, , );
I don't like the use of true to indicate a store here, when values other than 0
and 1 are possible.
Any reason not to use MMU_DATA_STORE?
A comment about fetch protection override might be nice here:
/*
* Since fetch protection override may apply to half of page 0 only,
* it need not be considered in the following.
*/
> +if (!pgm_code) {
> +/* Fetching permitted; storing permitted - but still check skeys */
> +skey = get_skey(abs_addr);
> +acc = (skey & SK_ACC_MASK) >> 4;
> +if (tp_acc != 0 && tp_acc != acc &&
> +!((env->cregs[0] & CR0_STOR_PROT_OVERRIDE) && acc == 9)) {
> +if (skey & SK_F) {
> +return 2;
> +} else {
> +return 1;
> +}
> +}
> return 0;
> }
>
> -if (env->int_pgm_code == PGM_PROTECTION) {
> +if (pgm_code == PGM_PROTECTION) {
> /* retry if reading is possible */
> -cs->exception_index = -1;
> -if (!s390_cpu_virt_mem_check_read(cpu, a1, 0, 1)) {
> +pgm_code = mmu_translate(env, a1, false, asc, _addr, ,
> );
> +if (!pgm_code) {
> /* Fetching permitted; storing not permitted */
> +skey = get_skey(abs_addr);
> +acc = (skey & SK_ACC_MASK) >> 4;
> +if ((skey & SK_F) && tp_acc != 0 && tp_acc != acc &&
> +!((env->cregs[0] & CR0_STOR_PROT_OVERRIDE) && acc == 9)) {
> +return 2;
> +}
> return 1;
> }
> }
>
> -switch (env->int_pgm_code) {
> +switch (pgm_code) {
> case PGM_PROTECTION:
> /* Fetching not permitted;
