Skip to content

Commit

Permalink
target/nios2: Clean up handling of tlbmisc in do_exception
Browse files Browse the repository at this point in the history 
The 4 lower bits, D, PERM, BAD, DBL, are unconditionally set on any
exception with EH=0, or so says Table 42 (Processor Status After
Taking Exception).

We currently do not set PERM or BAD at all, and only set/clear
DBL for tlb miss, and do not clear DBL for any other exception.

It is a bit confusing to set D in tlb_fill and the rest during
do_interrupt, so move the setting of D to do_interrupt as well.
To do this, split EXP_TLBD into two cases, EXCP_TLB_X and EXCP_TLB_D,
which allows us to distinguish them during do_interrupt.  Choose
a value for EXCP_TLB_D such that when truncated it produces the
correct value for exception.CAUSE.

Rename EXCP_TLB[RWX] to EXCP_PERM_[RWX], to emphasize that the
exception is permissions related.  Rename EXCP_SUPER[AD] to
EXCP_SUPERA_[DX] to emphasize that they are both "supervisor
address" exceptions, data and execute.

Retain the setting of tlbmisc.WE for the fast-tlb-miss path, as it
is being relied upon, but remove it from the permission path.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220421151735.31996-37-richard.henderson@linaro.org>
  • Loading branch information
@rth7680
rth7680 committed Apr 26, 2022
1 parent 34cccb7 commit be77e1d
Show file tree
Hide file tree
Showing 2 changed files with 73 additions and 37 deletions.
13 changes: 7 additions & 6 deletions target/nios2/cpu.h
View file
Expand Up @@ -166,13 +166,14 @@ FIELD(CR_TLBMISC, EE, 24, 1)
#define EXCP_UNALIGN 6
#define EXCP_UNALIGND 7
#define EXCP_DIV 8
#define EXCP_SUPERA 9
#define EXCP_SUPERA_X 9
#define EXCP_SUPERI 10
#define EXCP_SUPERD 11
#define EXCP_TLBD 12
#define EXCP_TLBX 13
#define EXCP_TLBR 14
#define EXCP_TLBW 15
#define EXCP_SUPERA_D 11
#define EXCP_TLB_X 12
#define EXCP_TLB_D (0x1000 | EXCP_TLB_X)
#define EXCP_PERM_X 13
#define EXCP_PERM_R 14
#define EXCP_PERM_W 15
#define EXCP_MPUI 16
#define EXCP_MPUD 17

Expand Down
97 changes: 66 additions & 31 deletions target/nios2/helper.c
View file
Expand Up @@ -29,7 +29,8 @@
#include "semihosting/semihost.h"


static void do_exception(Nios2CPU *cpu, uint32_t exception_addr, bool is_break)
static void do_exception(Nios2CPU *cpu, uint32_t exception_addr,
uint32_t tlbmisc_set, bool is_break)
{
CPUNios2State *env = &cpu->env;
CPUState *cs = CPU(cpu);
Expand All @@ -48,6 +49,16 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr, bool is_break)

if (cpu->mmu_present) {
new_status |= CR_STATUS_EH;

/*
* There are 4 bits that are always written.
* Explicitly clear them, to be set via the argument.
*/
env->ctrl[CR_TLBMISC] &= ~(CR_TLBMISC_D |
CR_TLBMISC_PERM |
CR_TLBMISC_BAD |
CR_TLBMISC_DBL);
env->ctrl[CR_TLBMISC] |= tlbmisc_set;
}
}

Expand All @@ -63,13 +74,14 @@ static void do_exception(Nios2CPU *cpu, uint32_t exception_addr, bool is_break)

static void do_iic_irq(Nios2CPU *cpu)
{
do_exception(cpu, cpu->exception_addr, false);
do_exception(cpu, cpu->exception_addr, 0, false);
}

void nios2_cpu_do_interrupt(CPUState *cs)
{
Nios2CPU *cpu = NIOS2_CPU(cs);
CPUNios2State *env = &cpu->env;
uint32_t tlbmisc_set = 0;

if (qemu_loglevel_mask(CPU_LOG_INT)) {
const char *name = NULL;
Expand All @@ -78,20 +90,21 @@ void nios2_cpu_do_interrupt(CPUState *cs)
case EXCP_IRQ:
name = "interrupt";
break;
case EXCP_TLBD:
case EXCP_TLB_X:
case EXCP_TLB_D:
if (env->ctrl[CR_STATUS] & CR_STATUS_EH) {
name = "TLB MISS (double)";
} else {
name = "TLB MISS (fast)";
}
break;
case EXCP_TLBR:
case EXCP_TLBW:
case EXCP_TLBX:
case EXCP_PERM_R:
case EXCP_PERM_W:
case EXCP_PERM_X:
name = "TLB PERM";
break;
case EXCP_SUPERA:
case EXCP_SUPERD:
case EXCP_SUPERA_X:
case EXCP_SUPERA_D:
name = "SUPERVISOR (address)";
break;
case EXCP_SUPERI:
Expand Down Expand Up @@ -129,38 +142,57 @@ void nios2_cpu_do_interrupt(CPUState *cs)
do_iic_irq(cpu);
break;

case EXCP_TLBD:
if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
env->ctrl[CR_TLBMISC] &= ~CR_TLBMISC_DBL;
env->ctrl[CR_TLBMISC] |= CR_TLBMISC_WE;
do_exception(cpu, cpu->fast_tlb_miss_addr, false);
case EXCP_TLB_D:
tlbmisc_set = CR_TLBMISC_D;
/* fall through */
case EXCP_TLB_X:
if (env->ctrl[CR_STATUS] & CR_STATUS_EH) {
tlbmisc_set |= CR_TLBMISC_DBL;
/*
* Normally, we don't write to tlbmisc unless !EH,
* so do it manually for the double-tlb miss exception.
*/
env->ctrl[CR_TLBMISC] &= ~(CR_TLBMISC_D |
CR_TLBMISC_PERM |
CR_TLBMISC_BAD);
env->ctrl[CR_TLBMISC] |= tlbmisc_set;
do_exception(cpu, cpu->exception_addr, 0, false);
} else {
env->ctrl[CR_TLBMISC] |= CR_TLBMISC_DBL;
do_exception(cpu, cpu->exception_addr, false);
tlbmisc_set |= CR_TLBMISC_WE;
do_exception(cpu, cpu->fast_tlb_miss_addr, tlbmisc_set, false);
}
break;

case EXCP_TLBR:
case EXCP_TLBW:
case EXCP_TLBX:
if ((env->ctrl[CR_STATUS] & CR_STATUS_EH) == 0) {
env->ctrl[CR_TLBMISC] |= CR_TLBMISC_WE;
case EXCP_PERM_R:
case EXCP_PERM_W:
tlbmisc_set = CR_TLBMISC_D;
/* fall through */
case EXCP_PERM_X:
tlbmisc_set |= CR_TLBMISC_PERM;
if (!(env->ctrl[CR_STATUS] & CR_STATUS_EH)) {
tlbmisc_set |= CR_TLBMISC_WE;
}
do_exception(cpu, cpu->exception_addr, false);
do_exception(cpu, cpu->exception_addr, tlbmisc_set, false);
break;

case EXCP_SUPERA_D:
case EXCP_UNALIGN:
tlbmisc_set = CR_TLBMISC_D;
/* fall through */
case EXCP_SUPERA_X:
case EXCP_UNALIGND:
tlbmisc_set |= CR_TLBMISC_BAD;
do_exception(cpu, cpu->exception_addr, tlbmisc_set, false);
break;

case EXCP_SUPERA:
case EXCP_SUPERI:
case EXCP_SUPERD:
case EXCP_ILLEGAL:
case EXCP_TRAP:
case EXCP_UNALIGN:
case EXCP_UNALIGND:
do_exception(cpu, cpu->exception_addr, false);
do_exception(cpu, cpu->exception_addr, 0, false);
break;

case EXCP_BREAK:
do_exception(cpu, cpu->exception_addr, true);
do_exception(cpu, cpu->exception_addr, 0, true);
break;

case EXCP_SEMIHOST:
Expand Down Expand Up @@ -215,7 +247,7 @@ bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
{
Nios2CPU *cpu = NIOS2_CPU(cs);
CPUNios2State *env = &cpu->env;
unsigned int excp = EXCP_TLBD;
unsigned int excp;
target_ulong vaddr, paddr;
Nios2MMULookup lu;
unsigned int hit;
Expand All @@ -242,7 +274,8 @@ bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
if (probe) {
return false;
}
cs->exception_index = EXCP_SUPERA;
cs->exception_index = (access_type == MMU_INST_FETCH
? EXCP_SUPERA_X : EXCP_SUPERA_D);
env->ctrl[CR_BADADDR] = address;
cpu_loop_exit_restore(cs, retaddr);
}
Expand All @@ -263,8 +296,10 @@ bool nios2_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
}

/* Permission violation */
excp = (access_type == MMU_DATA_LOAD ? EXCP_TLBR :
access_type == MMU_DATA_STORE ? EXCP_TLBW : EXCP_TLBX);
excp = (access_type == MMU_DATA_LOAD ? EXCP_PERM_R :
access_type == MMU_DATA_STORE ? EXCP_PERM_W : EXCP_PERM_X);
} else {
excp = (access_type == MMU_INST_FETCH ? EXCP_TLB_X: EXCP_TLB_D);
}

if (probe) {
Expand Down

0 comments on commit be77e1d

Please sign in to comment.