* [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs
@ 2023-05-06 6:52 Richard Purdie
2023-05-06 7:27 ` Richard Henderson
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Richard Purdie @ 2023-05-06 6:52 UTC (permalink / raw)
To: qemu-devel
Cc: Víctor Colombo, Matheus Ferst, Daniel Henrique Barboza,
Richard Henderson
The following commits changed the code such that the fallback to MFSS for MFFSCRN,
MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:
bf8adfd88b547680aa857c46098f3a1e94373160 - target/ppc: Move mffscrn[i] to decodetree
394c2e2fda70da722f20fb60412d6c0ca4bfaa03 - target/ppc: Move mffsce to decodetree
3e5bce70efe6bd1f684efbb21fd2a316cbf0657e - target/ppc: Move mffsl to decodetree
The hardware will handle them as a MFFS instruction as the code did previously.
This means applications that were segfaulting under qemu when encountering these
instructions which is used in glibc libm functions for example.
The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.
This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
as the hardware decoder would, fixing the segfaulting libm code. It and also ensures
the MFSS instruction is used for currently reserved bits to handle other potential
ISA additions more correctly.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
target/ppc/insn32.decode | 19 ++++++++++++-------
target/ppc/translate/fp-impl.c.inc | 30 ++++++++++++++++++++++++------
2 files changed, 36 insertions(+), 13 deletions(-)
v2 - switch to use decodetree pattern groups per feedback
diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
index f8f589e9fd..3c4e2c2fc2 100644
--- a/target/ppc/insn32.decode
+++ b/target/ppc/insn32.decode
@@ -390,13 +390,18 @@ SETNBCR 011111 ..... ..... ----- 0111100000 - @X_bi
### Move To/From FPSCR
-MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
-MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
-MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
-MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
-MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
-MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
-MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
+{
+ # Before Power ISA v3.0, MFFS bits 11~15 were reserved and should be ignored
+ [
+ MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
+ MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
+ MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
+ MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
+ MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
+ MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
+ ]
+ MFFS 111111 ..... ----- ----- 1001000111 . @X_t_rc
+}
### Decimal Floating-Point Arithmetic Instructions
diff --git a/target/ppc/translate/fp-impl.c.inc b/target/ppc/translate/fp-impl.c.inc
index 57d8437851..10dfd91aa4 100644
--- a/target/ppc/translate/fp-impl.c.inc
+++ b/target/ppc/translate/fp-impl.c.inc
@@ -584,7 +584,10 @@ static bool trans_MFFSCE(DisasContext *ctx, arg_X_t *a)
{
TCGv_i64 fpscr;
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
gen_reset_fpstatus();
@@ -597,7 +600,10 @@ static bool trans_MFFSCRN(DisasContext *ctx, arg_X_tb *a)
{
TCGv_i64 t1, fpscr;
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
t1 = tcg_temp_new_i64();
@@ -614,7 +620,10 @@ static bool trans_MFFSCDRN(DisasContext *ctx, arg_X_tb *a)
{
TCGv_i64 t1, fpscr;
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
t1 = tcg_temp_new_i64();
@@ -631,7 +640,10 @@ static bool trans_MFFSCRNI(DisasContext *ctx, arg_X_imm2 *a)
{
TCGv_i64 t1, fpscr;
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
t1 = tcg_temp_new_i64();
@@ -647,7 +659,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
{
TCGv_i64 t1, fpscr;
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
t1 = tcg_temp_new_i64();
@@ -661,7 +676,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
static bool trans_MFFSL(DisasContext *ctx, arg_X_t *a)
{
- REQUIRE_INSNS_FLAGS2(ctx, ISA300);
+ if (!(ctx->insns_flags2 & PPC2_ISA300)) {
+ return false;
+ }
+
REQUIRE_FPU(ctx);
gen_reset_fpstatus();
--
2.39.2
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs
2023-05-06 6:52 [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs Richard Purdie
@ 2023-05-06 7:27 ` Richard Henderson
2023-05-08 12:11 ` Matheus K. Ferst
2023-05-10 7:28 ` Philippe Mathieu-Daudé
2 siblings, 0 replies; 5+ messages in thread
From: Richard Henderson @ 2023-05-06 7:27 UTC (permalink / raw)
To: Richard Purdie, qemu-devel
Cc: Víctor Colombo, Matheus Ferst, Daniel Henrique Barboza
On 5/6/23 07:52, Richard Purdie wrote:
> The following commits changed the code such that the fallback to MFSS for MFFSCRN,
> MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:
>
> bf8adfd88b547680aa857c46098f3a1e94373160 - target/ppc: Move mffscrn[i] to decodetree
> 394c2e2fda70da722f20fb60412d6c0ca4bfaa03 - target/ppc: Move mffsce to decodetree
> 3e5bce70efe6bd1f684efbb21fd2a316cbf0657e - target/ppc: Move mffsl to decodetree
>
> The hardware will handle them as a MFFS instruction as the code did previously.
> This means applications that were segfaulting under qemu when encountering these
> instructions which is used in glibc libm functions for example.
>
> The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.
>
> This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
> as the hardware decoder would, fixing the segfaulting libm code. It and also ensures
> the MFSS instruction is used for currently reserved bits to handle other potential
> ISA additions more correctly.
>
> Signed-off-by: Richard Purdie<richard.purdie@linuxfoundation.org>
> ---
> target/ppc/insn32.decode | 19 ++++++++++++-------
> target/ppc/translate/fp-impl.c.inc | 30 ++++++++++++++++++++++++------
> 2 files changed, 36 insertions(+), 13 deletions(-)
>
> v2 - switch to use decodetree pattern groups per feedback
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs
2023-05-06 6:52 [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs Richard Purdie
2023-05-06 7:27 ` Richard Henderson
@ 2023-05-08 12:11 ` Matheus K. Ferst
2023-05-10 8:05 ` Richard Henderson
2023-05-10 7:28 ` Philippe Mathieu-Daudé
2 siblings, 1 reply; 5+ messages in thread
From: Matheus K. Ferst @ 2023-05-08 12:11 UTC (permalink / raw)
To: Richard Purdie, qemu-devel
Cc: Víctor Colombo, Daniel Henrique Barboza, Richard Henderson
On 06/05/2023 03:52, Richard Purdie wrote:
> The following commits changed the code such that the fallback to MFSS for MFFSCRN,
> MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:
>
> bf8adfd88b547680aa857c46098f3a1e94373160 - target/ppc: Move mffscrn[i] to decodetree
> 394c2e2fda70da722f20fb60412d6c0ca4bfaa03 - target/ppc: Move mffsce to decodetree
> 3e5bce70efe6bd1f684efbb21fd2a316cbf0657e - target/ppc: Move mffsl to decodetree
>
> The hardware will handle them as a MFFS instruction as the code did previously.
> This means applications that were segfaulting under qemu when encountering these
> instructions which is used in glibc libm functions for example.
>
> The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.
>
> This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
> as the hardware decoder would, fixing the segfaulting libm code. It and also ensures
> the MFSS instruction is used for currently reserved bits to handle other potential
> ISA additions more correctly.
>
> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
> ---
> target/ppc/insn32.decode | 19 ++++++++++++-------
> target/ppc/translate/fp-impl.c.inc | 30 ++++++++++++++++++++++++------
> 2 files changed, 36 insertions(+), 13 deletions(-)
>
> v2 - switch to use decodetree pattern groups per feedback
>
> diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
> index f8f589e9fd..3c4e2c2fc2 100644
> --- a/target/ppc/insn32.decode
> +++ b/target/ppc/insn32.decode
> @@ -390,13 +390,18 @@ SETNBCR 011111 ..... ..... ----- 0111100000 - @X_bi
>
> ### Move To/From FPSCR
>
> -MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
> -MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
> -MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
> -MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
> -MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
> -MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
> -MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
> +{
> + # Before Power ISA v3.0, MFFS bits 11~15 were reserved and should be ignored
> + [
> + MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
> + MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
> + MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
> + MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
> + MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
> + MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
> + ]
> + MFFS 111111 ..... ----- ----- 1001000111 . @X_t_rc
> +}
>
> ### Decimal Floating-Point Arithmetic Instructions
>
> diff --git a/target/ppc/translate/fp-impl.c.inc b/target/ppc/translate/fp-impl.c.inc
> index 57d8437851..10dfd91aa4 100644
> --- a/target/ppc/translate/fp-impl.c.inc
> +++ b/target/ppc/translate/fp-impl.c.inc
> @@ -584,7 +584,10 @@ static bool trans_MFFSCE(DisasContext *ctx, arg_X_t *a)
> {
> TCGv_i64 fpscr;
>
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> gen_reset_fpstatus();
> @@ -597,7 +600,10 @@ static bool trans_MFFSCRN(DisasContext *ctx, arg_X_tb *a)
> {
> TCGv_i64 t1, fpscr;
>
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> t1 = tcg_temp_new_i64();
> @@ -614,7 +620,10 @@ static bool trans_MFFSCDRN(DisasContext *ctx, arg_X_tb *a)
> {
> TCGv_i64 t1, fpscr;
>
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> t1 = tcg_temp_new_i64();
> @@ -631,7 +640,10 @@ static bool trans_MFFSCRNI(DisasContext *ctx, arg_X_imm2 *a)
> {
> TCGv_i64 t1, fpscr;
>
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> t1 = tcg_temp_new_i64();
> @@ -647,7 +659,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
> {
> TCGv_i64 t1, fpscr;
>
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> t1 = tcg_temp_new_i64();
> @@ -661,7 +676,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
>
> static bool trans_MFFSL(DisasContext *ctx, arg_X_t *a)
> {
> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
> + return false;
> + }
> +
> REQUIRE_FPU(ctx);
>
> gen_reset_fpstatus();
> --
> 2.39.2
>
As mention in the v1 thread, we should validate bits 11~15 on Power ISA
v3.0+ to follow what the ISA says and keep the same behavior as the
hardware. Again, sorry for the delayed response.
Thanks,
Matheus K. Ferst
Instituto de Pesquisas ELDORADO <http://www.eldorado.org.br/>
Analista de Software
Aviso Legal - Disclaimer <https://www.eldorado.org.br/disclaimer.html>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs
2023-05-08 12:11 ` Matheus K. Ferst
@ 2023-05-10 8:05 ` Richard Henderson
0 siblings, 0 replies; 5+ messages in thread
From: Richard Henderson @ 2023-05-10 8:05 UTC (permalink / raw)
To: Matheus K. Ferst, Richard Purdie, qemu-devel
Cc: Víctor Colombo, Daniel Henrique Barboza
On 5/8/23 13:11, Matheus K. Ferst wrote:
> On 06/05/2023 03:52, Richard Purdie wrote:
>> The following commits changed the code such that the fallback to MFSS for MFFSCRN,
>> MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:
>>
>> bf8adfd88b547680aa857c46098f3a1e94373160 - target/ppc: Move mffscrn[i] to decodetree
>> 394c2e2fda70da722f20fb60412d6c0ca4bfaa03 - target/ppc: Move mffsce to decodetree
>> 3e5bce70efe6bd1f684efbb21fd2a316cbf0657e - target/ppc: Move mffsl to decodetree
>>
>> The hardware will handle them as a MFFS instruction as the code did previously.
>> This means applications that were segfaulting under qemu when encountering these
>> instructions which is used in glibc libm functions for example.
>>
>> The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.
>>
>> This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
>> as the hardware decoder would, fixing the segfaulting libm code. It and also ensures
>> the MFSS instruction is used for currently reserved bits to handle other potential
>> ISA additions more correctly.
>>
>> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
>> ---
>> target/ppc/insn32.decode | 19 ++++++++++++-------
>> target/ppc/translate/fp-impl.c.inc | 30 ++++++++++++++++++++++++------
>> 2 files changed, 36 insertions(+), 13 deletions(-)
>>
>> v2 - switch to use decodetree pattern groups per feedback
>>
>> diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
>> index f8f589e9fd..3c4e2c2fc2 100644
>> --- a/target/ppc/insn32.decode
>> +++ b/target/ppc/insn32.decode
>> @@ -390,13 +390,18 @@ SETNBCR 011111 ..... ..... ----- 0111100000 - @X_bi
>>
>> ### Move To/From FPSCR
>>
>> -MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
>> -MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
>> -MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
>> -MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
>> -MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
>> -MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
>> -MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
>> +{
>> + # Before Power ISA v3.0, MFFS bits 11~15 were reserved and should be ignored
>> + [
>> + MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
>> + MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
>> + MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
>> + MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
>> + MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
>> + MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
>> + ]
>> + MFFS 111111 ..... ----- ----- 1001000111 . @X_t_rc
>> +}
>>
>> ### Decimal Floating-Point Arithmetic Instructions
>>
>> diff --git a/target/ppc/translate/fp-impl.c.inc b/target/ppc/translate/fp-impl.c.inc
>> index 57d8437851..10dfd91aa4 100644
>> --- a/target/ppc/translate/fp-impl.c.inc
>> +++ b/target/ppc/translate/fp-impl.c.inc
>> @@ -584,7 +584,10 @@ static bool trans_MFFSCE(DisasContext *ctx, arg_X_t *a)
>> {
>> TCGv_i64 fpscr;
>>
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> gen_reset_fpstatus();
>> @@ -597,7 +600,10 @@ static bool trans_MFFSCRN(DisasContext *ctx, arg_X_tb *a)
>> {
>> TCGv_i64 t1, fpscr;
>>
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> t1 = tcg_temp_new_i64();
>> @@ -614,7 +620,10 @@ static bool trans_MFFSCDRN(DisasContext *ctx, arg_X_tb *a)
>> {
>> TCGv_i64 t1, fpscr;
>>
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> t1 = tcg_temp_new_i64();
>> @@ -631,7 +640,10 @@ static bool trans_MFFSCRNI(DisasContext *ctx, arg_X_imm2 *a)
>> {
>> TCGv_i64 t1, fpscr;
>>
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> t1 = tcg_temp_new_i64();
>> @@ -647,7 +659,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
>> {
>> TCGv_i64 t1, fpscr;
>>
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> t1 = tcg_temp_new_i64();
>> @@ -661,7 +676,10 @@ static bool trans_MFFSCDRNI(DisasContext *ctx, arg_X_imm3 *a)
>>
>> static bool trans_MFFSL(DisasContext *ctx, arg_X_t *a)
>> {
>> - REQUIRE_INSNS_FLAGS2(ctx, ISA300);
>> + if (!(ctx->insns_flags2 & PPC2_ISA300)) {
>> + return false;
>> + }
>> +
>> REQUIRE_FPU(ctx);
>>
>> gen_reset_fpstatus();
>> --
>> 2.39.2
>>
>
> As mention in the v1 thread, we should validate bits 11~15 on Power ISA v3.0+ to follow
> what the ISA says and keep the same behavior as the hardware. Again, sorry for the delayed
> response.
Thanks for double-checking. In that case the v1 patch is indeed better.
r~
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs
2023-05-06 6:52 [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs Richard Purdie
2023-05-06 7:27 ` Richard Henderson
2023-05-08 12:11 ` Matheus K. Ferst
@ 2023-05-10 7:28 ` Philippe Mathieu-Daudé
2 siblings, 0 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2023-05-10 7:28 UTC (permalink / raw)
To: Richard Purdie, qemu-devel
Cc: Víctor Colombo, Matheus Ferst, Daniel Henrique Barboza,
Richard Henderson
On 6/5/23 08:52, Richard Purdie wrote:
> The following commits changed the code such that the fallback to MFSS for MFFSCRN,
> MFFSCRNI, MFFSCE and MFFSL on pre 3.0 ISAs was removed and became an illegal instruction:
>
> bf8adfd88b547680aa857c46098f3a1e94373160 - target/ppc: Move mffscrn[i] to decodetree
> 394c2e2fda70da722f20fb60412d6c0ca4bfaa03 - target/ppc: Move mffsce to decodetree
> 3e5bce70efe6bd1f684efbb21fd2a316cbf0657e - target/ppc: Move mffsl to decodetree
>
> The hardware will handle them as a MFFS instruction as the code did previously.
> This means applications that were segfaulting under qemu when encountering these
> instructions which is used in glibc libm functions for example.
>
> The fallback for MFFSCDRN and MFFSCDRNI added in a later patch was also missing.
>
> This patch restores the fallback to MFSS for these instructions on pre 3.0s ISAs
> as the hardware decoder would, fixing the segfaulting libm code. It and also ensures
> the MFSS instruction is used for currently reserved bits to handle other potential
> ISA additions more correctly.
>
> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
> ---
> target/ppc/insn32.decode | 19 ++++++++++++-------
> target/ppc/translate/fp-impl.c.inc | 30 ++++++++++++++++++++++++------
> 2 files changed, 36 insertions(+), 13 deletions(-)
>
> v2 - switch to use decodetree pattern groups per feedback
>
> diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode
> index f8f589e9fd..3c4e2c2fc2 100644
> --- a/target/ppc/insn32.decode
> +++ b/target/ppc/insn32.decode
> @@ -390,13 +390,18 @@ SETNBCR 011111 ..... ..... ----- 0111100000 - @X_bi
>
> ### Move To/From FPSCR
>
> -MFFS 111111 ..... 00000 ----- 1001000111 . @X_t_rc
> -MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
> -MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
> -MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
> -MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
> -MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
> -MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
> +{
> + # Before Power ISA v3.0, MFFS bits 11~15 were reserved and should be ignored
> + [
> + MFFSCE 111111 ..... 00001 ----- 1001000111 - @X_t
> + MFFSCRN 111111 ..... 10110 ..... 1001000111 - @X_tb
> + MFFSCDRN 111111 ..... 10100 ..... 1001000111 - @X_tb
> + MFFSCRNI 111111 ..... 10111 ---.. 1001000111 - @X_imm2
> + MFFSCDRNI 111111 ..... 10101 --... 1001000111 - @X_imm3
> + MFFSL 111111 ..... 11000 ----- 1001000111 - @X_t
> + ]
> + MFFS 111111 ..... ----- ----- 1001000111 . @X_t_rc
> +}
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Fixes: bf8adfd88b ("target/ppc: Move mffscrn[i] to decodetree")
Fixes: 394c2e2fda ("target/ppc: Move mffsce to decodetree")
Fixes: 3e5bce70ef ("target/ppc: Move mffsl to decodetree")
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-05-10 8:06 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2023-05-06 6:52 [PATCH v2] target/ppc: Fix fallback to MFSS for MFFS* instructions on pre 3.0 ISAs Richard Purdie
2023-05-06 7:27 ` Richard Henderson
2023-05-08 12:11 ` Matheus K. Ferst
2023-05-10 8:05 ` Richard Henderson
2023-05-10 7:28 ` Philippe Mathieu-Daudé
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