powerpc/64s: avoid reloading (H)SRR registers if they are still valid

When an interrupt is taken, the SRR registers are set to return to where
it left off. Unless they are modified in the meantime, or the return
address or MSR are modified, there is no need to reload these registers
when returning from interrupt.

Introduce per-CPU flags that track the validity of SRR and HSRR
registers. These are cleared when returning from interrupt, when
using the registers for something else (e.g., OPAL calls), when
adjusting the return address or MSR of a context, and when context
switching (which changes the return address and MSR).

This improves the performance of interrupt returns.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold in fixup patch from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com

7 files changed, 42 insertions, 9 deletions

diff --git a/arch/powerpc/platforms/embedded6xx/holly.c b/arch/powerpc/platforms/embedded6xx/holly.c
index 53065d564161..85521b3e7098 100644
--- a/arch/powerpc/platforms/embedded6xx/holly.c
+++ b/arch/powerpc/platforms/embedded6xx/holly.c
@@ -251,8 +251,8 @@ static int ppc750_machine_check_exception(struct pt_regs *regs)
 	/* Are we prepared to handle this fault */
 	if ((entry = search_exception_tables(regs->nip)) != NULL) {
 		tsi108_clear_pci_cfg_error();
-		regs->msr |= MSR_RI;
-		regs->nip = extable_fixup(entry);
+		regs_set_return_msr(regs, regs->msr | MSR_RI);
+		regs_set_return_ip(regs, extable_fixup(entry));
 		return 1;
 	}
 	return 0;
diff --git a/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c b/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
index 5565647dc879..d8da6a483e59 100644
--- a/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
+++ b/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
@@ -173,8 +173,8 @@ static int mpc7448_machine_check_exception(struct pt_regs *regs)
 	/* Are we prepared to handle this fault */
 	if ((entry = search_exception_tables(regs->nip)) != NULL) {
 		tsi108_clear_pci_cfg_error();
-		regs->msr |= MSR_RI;
-		regs->nip = extable_fixup(entry);
+		regs_set_return_msr(regs, regs->msr | MSR_RI);
+		regs_set_return_ip(regs, extable_fixup(entry));
 		return 1;
 	}
 	return 0;
diff --git a/arch/powerpc/platforms/pasemi/idle.c b/arch/powerpc/platforms/pasemi/idle.c
index 1c954c90b0f4..9b88e3cded7d 100644
--- a/arch/powerpc/platforms/pasemi/idle.c
+++ b/arch/powerpc/platforms/pasemi/idle.c
@@ -37,7 +37,7 @@ static int pasemi_system_reset_exception(struct pt_regs *regs)
 	 */
 
 	if (regs->msr & SRR1_WAKEMASK)
-		regs->nip = regs->link;
+		regs_set_return_ip(regs, regs->link);
 
 	switch (regs->msr & SRR1_WAKEMASK) {
 	case SRR1_WAKEDEC:
@@ -58,7 +58,7 @@ static int pasemi_system_reset_exception(struct pt_regs *regs)
 	restore_astate(hard_smp_processor_id());
 
 	/* everything handled */
-	regs->msr |= MSR_RI;
+	regs_set_return_msr(regs, regs->msr | MSR_RI);
 	return 1;
 }
 
diff --git a/arch/powerpc/platforms/powernv/opal-call.c b/arch/powerpc/platforms/powernv/opal-call.c
index 01401e3da7ca..f812c74c61e5 100644
--- a/arch/powerpc/platforms/powernv/opal-call.c
+++ b/arch/powerpc/platforms/powernv/opal-call.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/percpu.h>
 #include <linux/jump_label.h>
+#include <asm/interrupt.h>
 #include <asm/opal-api.h>
 #include <asm/trace.h>
 #include <asm/asm-prototypes.h>
@@ -100,6 +101,9 @@ static int64_t opal_call(int64_t a0, int64_t a1, int64_t a2, int64_t a3,
 	bool mmu = (msr & (MSR_IR|MSR_DR));
 	int64_t ret;
 
+	/* OPAL call / firmware may use SRR and/or HSRR */
+	srr_regs_clobbered();
+
 	msr &= ~MSR_EE;
 
 	if (unlikely(!mmu))
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 303d7c775740..2835376e61a4 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -773,7 +773,7 @@ bool opal_mce_check_early_recovery(struct pt_regs *regs)
 	 * Setup regs->nip to rfi into fixup address.
 	 */
 	if (recover_addr)
-		regs->nip = recover_addr;
+		regs_set_return_ip(regs, recover_addr);
 
 out:
 	return !!recover_addr;
diff --git a/arch/powerpc/platforms/pseries/hvCall.S b/arch/powerpc/platforms/pseries/hvCall.S
index 8a2b8d64265b..ab9fc6506861 100644
--- a/arch/powerpc/platforms/pseries/hvCall.S
+++ b/arch/powerpc/platforms/pseries/hvCall.S
@@ -108,6 +108,10 @@ _GLOBAL_TOC(plpar_hcall_norets_notrace)
 	mfcr	r0
 	stw	r0,8(r1)
 	HVSC				/* invoke the hypervisor */
+
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 	blr				/* return r3 = status */
@@ -120,6 +124,9 @@ _GLOBAL_TOC(plpar_hcall_norets)
 	HCALL_BRANCH(plpar_hcall_norets_trace)
 	HVSC				/* invoke the hypervisor */
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 	blr				/* return r3 = status */
@@ -129,6 +136,10 @@ plpar_hcall_norets_trace:
 	HCALL_INST_PRECALL(R4)
 	HVSC
 	HCALL_INST_POSTCALL_NORETS
+
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 	blr
@@ -159,6 +170,9 @@ _GLOBAL_TOC(plpar_hcall)
 	std	r6, 16(r12)
 	std	r7, 24(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
@@ -188,6 +202,9 @@ plpar_hcall_trace:
 
 	HCALL_INST_POSTCALL(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
@@ -223,6 +240,9 @@ _GLOBAL(plpar_hcall_raw)
 	std	r6, 16(r12)
 	std	r7, 24(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
@@ -262,6 +282,9 @@ _GLOBAL_TOC(plpar_hcall9)
 	std	r11,56(r12)
 	std	r0, 64(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
@@ -300,6 +323,9 @@ plpar_hcall9_trace:
 
 	HCALL_INST_POSTCALL(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
@@ -339,6 +365,9 @@ _GLOBAL(plpar_hcall9_raw)
 	std	r11,56(r12)
 	std	r0, 64(r12)
 
+	li	r4,0
+	stb	r4,PACASRR_VALID(r13)
+
 	lwz	r0,8(r1)
 	mtcrf	0xff,r0
 
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 2f636308cf60..167f2e1b8d39 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -487,8 +487,8 @@ int pSeries_system_reset_exception(struct pt_regs *regs)
 	if ((be64_to_cpu(regs->msr) &
 			(MSR_LE|MSR_RI|MSR_DR|MSR_IR|MSR_ME|MSR_PR|
 			 MSR_ILE|MSR_HV|MSR_SF)) == (MSR_DR|MSR_SF)) {
-		regs->nip = be64_to_cpu((__be64)regs->nip);
-		regs->msr = 0;
+		regs_set_return_ip(regs, be64_to_cpu((__be64)regs->nip));
+		regs_set_return_msr(regs, 0);
 	}
 #endif