powerpc/tm: Save and restore AMR on treclaim and trechkpt

Althought AMR is stashed in the checkpoint area, currently we don't save
it to the per thread checkpoint struct after a treclaim and so we don't
restore it either from that struct when we trechkpt. As a consequence when
the transaction is later rolled back the kernel space AMR value when the
trechkpt was done appears in userspace.

That commit saves and restores AMR accordingly on treclaim and trechkpt.
Since AMR value is also used in kernel space in other functions, it also
takes care of stashing kernel live AMR into the stack before treclaim and
before trechkpt, restoring it later, just before returning from tm_reclaim
and __tm_recheckpoint.

Is also fixes two nonrelated comments about CR and MSR.

Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200919150025.9609-1-gromero@linux.ibm.com

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 22ffe85..365290b 100644 (file)
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -220,6 +220,7 @@ struct thread_struct {
        unsigned long   tm_tar;
        unsigned long   tm_ppr;
        unsigned long   tm_dscr;
+       unsigned long   tm_amr;
 
        /*
         * Checkpointed FP and VSX 0-31 register set.

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 8711c21..c2722ff 100644 (file)
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -176,6 +176,7 @@ int main(void)
        OFFSET(THREAD_TM_TAR, thread_struct, tm_tar);
        OFFSET(THREAD_TM_PPR, thread_struct, tm_ppr);
        OFFSET(THREAD_TM_DSCR, thread_struct, tm_dscr);
+       OFFSET(THREAD_TM_AMR, thread_struct, tm_amr);
        OFFSET(PT_CKPT_REGS, thread_struct, ckpt_regs);
        OFFSET(THREAD_CKVRSTATE, thread_struct, ckvr_state.vr);
        OFFSET(THREAD_CKVRSAVE, thread_struct, ckvrsave);

diff --git a/arch/powerpc/kernel/tm.S b/arch/powerpc/kernel/tm.S
index 6ba0fdd..2b91f23 100644 (file)
--- a/arch/powerpc/kernel/tm.S
+++ b/arch/powerpc/kernel/tm.S
@@ -122,6 +122,13 @@ _GLOBAL(tm_reclaim)
        std     r3, STK_PARAM(R3)(r1)
        SAVE_NVGPRS(r1)
 
+       /*
+        * Save kernel live AMR since it will be clobbered by treclaim
+        * but can be used elsewhere later in kernel space.
+        */
+       mfspr   r3, SPRN_AMR
+       std     r3, TM_FRAME_L1(r1)
+
        /* We need to setup MSR for VSX register save instructions. */
        mfmsr   r14
        mr      r15, r14
@@ -245,7 +252,7 @@ _GLOBAL(tm_reclaim)
         * but is used in signal return to 'wind back' to the abort handler.
         */
 
-       /* ******************** CR,LR,CCR,MSR ********** */
+       /* ***************** CTR, LR, CR, XER ********** */
        mfctr   r3
        mflr    r4
        mfcr    r5
@@ -256,7 +263,6 @@ _GLOBAL(tm_reclaim)
        std     r5, _CCR(r7)
        std     r6, _XER(r7)
 
-
        /* ******************** TAR, DSCR ********** */
        mfspr   r3, SPRN_TAR
        mfspr   r4, SPRN_DSCR
@@ -264,6 +270,10 @@ _GLOBAL(tm_reclaim)
        std     r3, THREAD_TM_TAR(r12)
        std     r4, THREAD_TM_DSCR(r12)
 
+        /* ******************** AMR **************** */
+        mfspr  r3, SPRN_AMR
+        std    r3, THREAD_TM_AMR(r12)
+
        /*
         * MSR and flags: We don't change CRs, and we don't need to alter MSR.
         */
@@ -308,7 +318,9 @@ _GLOBAL(tm_reclaim)
        std     r3, THREAD_TM_TFHAR(r12)
        std     r4, THREAD_TM_TFIAR(r12)
 
-       /* AMR is checkpointed too, but is unsupported by Linux. */
+       /* Restore kernel live AMR */
+       ld      r8, TM_FRAME_L1(r1)
+       mtspr   SPRN_AMR, r8
 
        /* Restore original MSR/IRQ state & clear TM mode */
        ld      r14, TM_FRAME_L0(r1)            /* Orig MSR */
@@ -355,6 +367,13 @@ _GLOBAL(__tm_recheckpoint)
         */
        SAVE_NVGPRS(r1)
 
+       /*
+        * Save kernel live AMR since it will be clobbered for trechkpt
+        * but can be used elsewhere later in kernel space.
+        */
+       mfspr   r8, SPRN_AMR
+       std     r8, TM_FRAME_L0(r1)
+
        /* Load complete register state from ts_ckpt* registers */
 
        addi    r7, r3, PT_CKPT_REGS            /* Thread's ckpt_regs */
@@ -404,7 +423,7 @@ _GLOBAL(__tm_recheckpoint)
 
 restore_gprs:
 
-       /* ******************** CR,LR,CCR,MSR ********** */
+       /* ****************** CTR, LR, XER ************* */
        ld      r4, _CTR(r7)
        ld      r5, _LINK(r7)
        ld      r8, _XER(r7)
@@ -417,6 +436,10 @@ restore_gprs:
        ld      r4, THREAD_TM_TAR(r3)
        mtspr   SPRN_TAR,       r4
 
+       /* ******************** AMR ******************** */
+       ld      r4, THREAD_TM_AMR(r3)
+       mtspr   SPRN_AMR, r4
+
        /* Load up the PPR and DSCR in GPRs only at this stage */
        ld      r5, THREAD_TM_DSCR(r3)
        ld      r6, THREAD_TM_PPR(r3)
@@ -509,6 +532,10 @@ restore_gprs:
        li      r4, MSR_RI
        mtmsrd  r4, 1
 
+       /* Restore kernel live AMR */
+       ld      r8, TM_FRAME_L0(r1)
+       mtspr   SPRN_AMR, r8
+
        REST_NVGPRS(r1)
 
        addi    r1, r1, TM_FRAME_SIZE