On Wed, 2025-05-14 at 18:38 +0200, Claudio Imbrenda wrote:
> Refactor some functions in priv.c to make them more readable.
>
> handle_{iske,rrbe,sske}: move duplicated checks into a single function.
> handle{pfmf,epsw}: improve readability.
> handle_lpswe{,y}: merge implementations since they are almost the same.
>
> Use u64_replace_bits() where it makes sense.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> arch/s390/kvm/kvm-s390.h | 15 ++
> arch/s390/kvm/priv.c | 288 ++++++++++++++++++---------------------
> 2 files changed, 148 insertions(+), 155 deletions(-)
>
[...]
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 758cefb5bac7..1a26aa591c2e 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -14,6 +14,7 @@
> #include <linux/mm_types.h>
> #include <linux/pgtable.h>
> #include <linux/io.h>
> +#include <linux/bitfield.h>
> #include <asm/asm-offsets.h>
> #include <asm/facility.h>
> #include <asm/current.h>
> @@ -253,29 +254,50 @@ static int try_handle_skey(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +struct skeys_ops_state {
> + int reg1;
> + int reg2;
> + int rc;
> + unsigned long gaddr;
> +};
> +
> +static bool skeys_common_checks(struct kvm_vcpu *vcpu, struct skeys_ops_state *state, bool abs)
> +{
> + if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE) {
> + state->rc = kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> + return true;
> + }
> +
> + state->rc = try_handle_skey(vcpu);
> + if (state->rc)
> + return true;
> +
> + kvm_s390_get_regs_rre(vcpu, &state->reg1, &state->reg2);
> +
> + state->gaddr = vcpu->run->s.regs.gprs[state->reg2] & PAGE_MASK;
> + state->gaddr = kvm_s390_logical_to_effective(vcpu, state->gaddr);
> + if (!abs)
> + state->gaddr = kvm_s390_real_to_abs(vcpu, state->gaddr);
> +
> + return false;
> +}
I don't really like this function, IMO it makes the calling functions harder to read.
If it was just a chain of checks it be fine, but with the differing control flow
base on the abs parameter and the complex return value it becomes too complicated.
> +
> static int handle_iske(struct kvm_vcpu *vcpu)
> {
> - unsigned long gaddr, vmaddr;
> + struct skeys_ops_state state;
> + unsigned long vmaddr;
> unsigned char key;
> - int reg1, reg2;
> bool unlocked;
> + u64 *r1;
> int rc;
>
> vcpu->stat.instruction_iske++;
>
> - if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> - return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
How about a macro INJECT_PGM_ON: INJECT_PGM_ON(kvm_s390_problem_state(vcpu), PGM_PRIVILEGED_OP)
> -
> - rc = try_handle_skey(vcpu);
> - if (rc)
> - return rc != -EAGAIN ? rc : 0;
You are not replicating this behavior, are you?
> -
> - kvm_s390_get_regs_rre(vcpu, ®1, ®2);
You could introduce a helper
void _kvm_s390_get_gpr_ptrs_rre(vcpu, u64 **reg1, u64 **reg2)
{
int r1, r2;
kvm_s390_get_regs_rre(vcpu, &r1, &r2);
*reg1 = &vcpu->run->s.regs.gprs[r1];
*reg2 = &vcpu->run->s.regs.gprs[r2];
}
which would remove some clutter from the original function implementations.
> + if (skeys_common_checks(vcpu, &state, false))
> + return state.rc;
> + r1 = vcpu->run->s.regs.gprs + state.reg1;
>
> - gaddr = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> - gaddr = kvm_s390_logical_to_effective(vcpu, gaddr);
> - gaddr = kvm_s390_real_to_abs(vcpu, gaddr);
> - vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(gaddr));
> + vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(state.gaddr));
> if (kvm_is_error_hva(vmaddr))
> return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> retry:
> @@ -296,33 +318,23 @@ static int handle_iske(struct kvm_vcpu *vcpu)
> return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> if (rc < 0)
> return rc;
> - vcpu->run->s.regs.gprs[reg1] &= ~0xff;
> - vcpu->run->s.regs.gprs[reg1] |= key;
> + *r1 = u64_replace_bits(*r1, key, 0xff);
> return 0;
> }
>
>
[...]
> retry:
> @@ -353,40 +365,30 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
> static int handle_sske(struct kvm_vcpu *vcpu)
> {
> unsigned char m3 = vcpu->arch.sie_block->ipb >> 28;
> + struct skeys_ops_state state;
> unsigned long start, end;
> unsigned char key, oldkey;
> - int reg1, reg2;
> + bool nq, mr, mc, mb;
> bool unlocked;
> + u64 *r1, *r2;
> int rc;
>
> vcpu->stat.instruction_sske++;
>
> - if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> - return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> -
> - rc = try_handle_skey(vcpu);
> - if (rc)
> - return rc != -EAGAIN ? rc : 0;
> -
> - if (!test_kvm_facility(vcpu->kvm, 8))
> - m3 &= ~SSKE_MB;
> - if (!test_kvm_facility(vcpu->kvm, 10))
> - m3 &= ~(SSKE_MC | SSKE_MR);
> - if (!test_kvm_facility(vcpu->kvm, 14))
> - m3 &= ~SSKE_NQ;
> + mb = test_kvm_facility(vcpu->kvm, 8) && (m3 & SSKE_MB);
> + mr = test_kvm_facility(vcpu->kvm, 10) && (m3 & SSKE_MR);
> + mc = test_kvm_facility(vcpu->kvm, 10) && (m3 & SSKE_MC);
> + nq = test_kvm_facility(vcpu->kvm, 14) && (m3 & SSKE_NQ);
That is indeed much nicer.
>
> - kvm_s390_get_regs_rre(vcpu, ®1, ®2);
> + /* start already designates an absolute address if MB is set */
> + if (skeys_common_checks(vcpu, &state, mb))
> + return state.rc;
>
> - key = vcpu->run->s.regs.gprs[reg1] & 0xfe;
> - start = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> - start = kvm_s390_logical_to_effective(vcpu, start);
> - if (m3 & SSKE_MB) {
> - /* start already designates an absolute address */
> - end = (start + _SEGMENT_SIZE) & ~(_SEGMENT_SIZE - 1);
> - } else {
> - start = kvm_s390_real_to_abs(vcpu, start);
> - end = start + PAGE_SIZE;
> - }
> + start = state.gaddr;
> + end = mb ? ALIGN(start + 1, _SEGMENT_SIZE) : start + PAGE_SIZE;
Alternatively you could do ALIGN_DOWN(start, _SEGMENT_SIZE) + _SEGMENT_SIZE,
which seems a bit easier to read, but it's really minor.
> + r1 = vcpu->run->s.regs.gprs + state.reg1;
> + r2 = vcpu->run->s.regs.gprs + state.reg2;
> + key = *r1 & 0xfe;
>
> while (start != end) {
> unsigned long vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(start));
> @@ -396,9 +398,7 @@ static int handle_sske(struct kvm_vcpu *vcpu)
> return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>
> mmap_read_lock(current->mm);
> - rc = cond_set_guest_storage_key(current->mm, vmaddr, key, &oldkey,
> - m3 & SSKE_NQ, m3 & SSKE_MR,
> - m3 & SSKE_MC);
> + rc = cond_set_guest_storage_key(current->mm, vmaddr, key, &oldkey, nq, mr, mc);
>
> if (rc < 0) {
> rc = fixup_user_fault(current->mm, vmaddr,
> @@ -415,23 +415,21 @@ static int handle_sske(struct kvm_vcpu *vcpu)
> start += PAGE_SIZE;
> }
>
> - if (m3 & (SSKE_MC | SSKE_MR)) {
> - if (m3 & SSKE_MB) {
> + if (mc || mr) {
> + if (mb) {
> /* skey in reg1 is unpredictable */
> kvm_s390_set_psw_cc(vcpu, 3);
> } else {
> kvm_s390_set_psw_cc(vcpu, rc);
> - vcpu->run->s.regs.gprs[reg1] &= ~0xff00UL;
> - vcpu->run->s.regs.gprs[reg1] |= (u64) oldkey << 8;
> + *r1 = u64_replace_bits(*r1, oldkey << 8, 0xff00);
Uh, u64_replace_bits does the shift for you, no?
So it should be u64_replace_bits(*r1, oldkey, 0xff00)
You could also do u64p_replace_bits(r1, oldkey, 0xff00) but I'd actually prefer the assignment
as you do it.
> }
> }
> - if (m3 & SSKE_MB) {
> - if (psw_bits(vcpu->arch.sie_block->gpsw).eaba == PSW_BITS_AMODE_64BIT)
> - vcpu->run->s.regs.gprs[reg2] &= ~PAGE_MASK;
> - else
> - vcpu->run->s.regs.gprs[reg2] &= ~0xfffff000UL;
> + if (mb) {
> end = kvm_s390_logical_to_effective(vcpu, end);
> - vcpu->run->s.regs.gprs[reg2] |= end;
> + if (kvm_s390_is_amode_64(vcpu))
> + *r2 = u64_replace_bits(*r2, end, PAGE_MASK);
> + else
> + *r2 = u64_replace_bits(*r2, end, 0xfffff000);
This does not work because of the implicit shift.
So you need to use gpa_to_gfn(end) instead.
(I think I would prefer using start instead of end, since it better shows
the interruptible nature of the instruction, but start == end if
we get here so ...)
> }
> return 0;
> }
> @@ -773,46 +771,28 @@ int kvm_s390_handle_lpsw(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> -static int handle_lpswe(struct kvm_vcpu *vcpu)
> +static int handle_lpswe_y(struct kvm_vcpu *vcpu, bool lpswey)
> {
> psw_t new_psw;
> u64 addr;
> int rc;
> u8 ar;
>
> - vcpu->stat.instruction_lpswe++;
> -
> - if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> - return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> -
> - addr = kvm_s390_get_base_disp_s(vcpu, &ar);
> - if (addr & 7)
> - return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> - rc = read_guest(vcpu, addr, ar, &new_psw, sizeof(new_psw));
> - if (rc)
> - return kvm_s390_inject_prog_cond(vcpu, rc);
> - vcpu->arch.sie_block->gpsw = new_psw;
> - if (!is_valid_psw(&vcpu->arch.sie_block->gpsw))
> - return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> - return 0;
> -}
> -
> -static int handle_lpswey(struct kvm_vcpu *vcpu)
> -{
> - psw_t new_psw;
> - u64 addr;
> - int rc;
> - u8 ar;
> -
> - vcpu->stat.instruction_lpswey++;
> + if (lpswey)
> + vcpu->stat.instruction_lpswey++;
> + else
> + vcpu->stat.instruction_lpswe++;
>
> - if (!test_kvm_facility(vcpu->kvm, 193))
> + if (lpswey && !test_kvm_facility(vcpu->kvm, 193))
> return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
>
> if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>
> - addr = kvm_s390_get_base_disp_siy(vcpu, &ar);
> + if (!lpswey)
> + addr = kvm_s390_get_base_disp_s(vcpu, &ar);
> + else
> + addr = kvm_s390_get_base_disp_siy(vcpu, &ar);
> if (addr & 7)
> return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
I'd prefer a helper function _do_lpswe_y_swap(struct kvm_vcpu *vcpu, gpa_t addr)
and then just
static int handle_lpswey(struct kvm_vcpu *vcpu)
{
u64 addr;
u8 ar;
vcpu->stat.instruction_lpswey++;
if (!test_kvm_facility(vcpu->kvm, 193))
return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
addr = kvm_s390_get_base_disp_siy(vcpu, &ar);
return _do_lpswe_y_swap(vcpu, addr);
}
Makes it easier to read IMO because of the simpler control flow.
>
> @@ -1034,7 +1014,7 @@ int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
> case 0xb1:
> return handle_stfl(vcpu);
> case 0xb2:
> - return handle_lpswe(vcpu);
> + return handle_lpswe_y(vcpu, false);
> default:
> return -EOPNOTSUPP;
> }
> @@ -1043,42 +1023,50 @@ int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
> static int handle_epsw(struct kvm_vcpu *vcpu)
> {
> int reg1, reg2;
> + u64 *r1, *r2;
>
> vcpu->stat.instruction_epsw++;
>
> kvm_s390_get_regs_rre(vcpu, ®1, ®2);
> + r1 = vcpu->run->s.regs.gprs + reg1;
> + r2 = vcpu->run->s.regs.gprs + reg2;
>
> /* This basically extracts the mask half of the psw. */
> - vcpu->run->s.regs.gprs[reg1] &= 0xffffffff00000000UL;
> - vcpu->run->s.regs.gprs[reg1] |= vcpu->arch.sie_block->gpsw.mask >> 32;
> - if (reg2) {
> - vcpu->run->s.regs.gprs[reg2] &= 0xffffffff00000000UL;
> - vcpu->run->s.regs.gprs[reg2] |=
> - vcpu->arch.sie_block->gpsw.mask & 0x00000000ffffffffUL;
> - }
> + *r1 = u64_replace_bits(*r1, vcpu->arch.sie_block->gpsw.mask >> 32, 0xffffffff);
> + if (reg2)
> + *r2 = u64_replace_bits(*r2, vcpu->arch.sie_block->gpsw.mask, 0xffffffff);
LGTM although I don't hate the original implementation, which is very easy to understand
compared to u64_replace_bits whose implementation is anything but.
It would be nice to make gprs a union, which I think should be fine from a backwards
compatibility point of view. So:
struct kvm_sync_regs {
__u64 prefix; /* prefix register */
union {
__u64 gprs[16]; /* general purpose registers */
struct { __u32 h; __u32 l} gprs32[16];
struct { __u16 hh; __u16 hl; ...} gprs16[16];
...
...
But I don't expect you to do the refactor.
You could of course also contribute documentation to bitfield.h :)
> return 0;
> }
[...]
> static int handle_pfmf(struct kvm_vcpu *vcpu)
> {
[...]
> - if (vcpu->run->s.regs.gprs[reg1] & PFMF_FSC) {
> - if (psw_bits(vcpu->arch.sie_block->gpsw).eaba == PSW_BITS_AMODE_64BIT) {
> - vcpu->run->s.regs.gprs[reg2] = end;
> - } else {
> - vcpu->run->s.regs.gprs[reg2] &= ~0xffffffffUL;
> - end = kvm_s390_logical_to_effective(vcpu, end);
> - vcpu->run->s.regs.gprs[reg2] |= end;
> - }
> + if (r1.fsc) {
> + u64 *r2 = vcpu->run->s.regs.gprs + reg2;
> +
> + end = kvm_s390_logical_to_effective(vcpu, end);
> + if (kvm_s390_is_amode_64(vcpu))
> + *r2 = u64_replace_bits(*r2, end, PAGE_MASK);
> + else
> + *r2 = u64_replace_bits(*r2, end, 0xfffff000);
Same issue as above regarding the shift.
> }
> return 0;
> }
> @@ -1361,8 +1338,9 @@ int kvm_s390_handle_lctl(struct kvm_vcpu *vcpu)
> reg = reg1;
> nr_regs = 0;
> do {
> - vcpu->arch.sie_block->gcr[reg] &= 0xffffffff00000000ul;
> - vcpu->arch.sie_block->gcr[reg] |= ctl_array[nr_regs++];
> + u64 *cr = vcpu->arch.sie_block->gcr + reg;
> +
> + *cr = u64_replace_bits(*cr, ctl_array[nr_regs++], 0xffffffff);
> if (reg == reg3)
> break;
> reg = (reg + 1) % 16;
> @@ -1489,7 +1467,7 @@ int kvm_s390_handle_eb(struct kvm_vcpu *vcpu)
> case 0x62:
> return handle_ri(vcpu);
> case 0x71:
> - return handle_lpswey(vcpu);
> + return handle_lpswe_y(vcpu, true);
> default:
> return -EOPNOTSUPP;
> }
--
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
