diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index c1a8aac01cf9..bb6f78fcf981 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -35,6 +35,19 @@
 /* PACA save area size in u64 units (exgen, exmc, etc) */
 #define EX_SIZE		10
 
+/* PACA save area offsets */
+#define EX_R9		0
+#define EX_R10		8
+#define EX_R11		16
+#define EX_R12		24
+#define EX_R13		32
+#define EX_DAR		40
+#define EX_DSISR	48
+#define EX_CCR		52
+#define EX_CFAR		56
+#define EX_PPR		64
+#define EX_CTR		72
+
 /*
  * maximum recursive depth of MCE exceptions
  */
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 4819bf60324c..03e2d65d3d3f 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -21,22 +21,6 @@
 #include <asm/feature-fixups.h>
 #include <asm/kup.h>
 
-/* PACA save area offsets (exgen, exmc, etc) */
-#define EX_R9		0
-#define EX_R10		8
-#define EX_R11		16
-#define EX_R12		24
-#define EX_R13		32
-#define EX_DAR		40
-#define EX_DSISR	48
-#define EX_CCR		52
-#define EX_CFAR		56
-#define EX_PPR		64
-#define EX_CTR		72
-.if EX_SIZE != 10
-	.error "EX_SIZE is wrong"
-.endif
-
 /*
  * Following are fixed section helper macros.
  *
@@ -1941,29 +1925,8 @@ EXC_VIRT_END(system_call, 0x4c00, 0x100)
 
 #ifdef CONFIG_KVM_BOOK3S_64_HANDLER
 TRAMP_REAL_BEGIN(system_call_kvm)
-	/*
-	 * This is a hcall, so register convention is as above, with these
-	 * differences:
-	 * r13 = PACA
-	 * ctr = orig r13
-	 * orig r10 saved in PACA
-	 */
-	 /*
-	  * Save the PPR (on systems that support it) before changing to
-	  * HMT_MEDIUM. That allows the KVM code to save that value into the
-	  * guest state (it is the guest's PPR value).
-	  */
-BEGIN_FTR_SECTION
-	mfspr	r10,SPRN_PPR
-	std	r10,HSTATE_PPR(r13)
-END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
-	HMT_MEDIUM
 	mfctr	r10
-	SET_SCRATCH0(r10)
-	mfcr	r10
-	std	r12,HSTATE_SCRATCH0(r13)
-	sldi	r12,r10,32
-	ori	r12,r12,0xc00
+	SET_SCRATCH0(r10) /* Save r13 in SCRATCH0 */
 #ifdef CONFIG_RELOCATABLE
 	/*
 	 * Requires __LOAD_FAR_HANDLER beause kvmppc_hcall lives
@@ -1971,15 +1934,12 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 */
 	__LOAD_FAR_HANDLER(r10, kvmppc_hcall)
 	mtctr   r10
-	ld	r10,PACA_EXGEN+EX_R10(r13)
 	bctr
 #else
-	ld	r10,PACA_EXGEN+EX_R10(r13)
 	b       kvmppc_hcall
 #endif
 #endif
 
-
 /**
  * Interrupt 0xd00 - Trace Interrupt.
  * This is a synchronous interrupt in response to instruction step or
diff --git a/arch/powerpc/kvm/book3s_64_entry.S b/arch/powerpc/kvm/book3s_64_entry.S
index c21fa64059ef..f527e16707db 100644
--- a/arch/powerpc/kvm/book3s_64_entry.S
+++ b/arch/powerpc/kvm/book3s_64_entry.S
@@ -14,6 +14,36 @@
 .global	kvmppc_hcall
 .balign IFETCH_ALIGN_BYTES
 kvmppc_hcall:
+	/*
+	 * This is a hcall, so register convention is as
+	 * Documentation/powerpc/papr_hcalls.rst, with these additions:
+	 * R13		= PACA
+	 * guest R13 saved in SPRN_SCRATCH0
+	 * R10		= free
+	 * guest r10 saved in PACA_EXGEN
+	 *
+	 * This may also be a syscall from PR-KVM userspace that is to be
+	 * reflected to the PR guest kernel, so registers may be set up for
+	 * a system call rather than hcall. We don't currently clobber
+	 * anything here, but the 0xc00 handler has already clobbered CTR
+	 * and CR0, so PR-KVM can not support a guest kernel that preserves
+	 * those registers across its system calls.
+	 */
+	 /*
+	  * Save the PPR (on systems that support it) before changing to
+	  * HMT_MEDIUM. That allows the KVM code to save that value into the
+	  * guest state (it is the guest's PPR value).
+	  */
+BEGIN_FTR_SECTION
+	mfspr	r10,SPRN_PPR
+	std	r10,HSTATE_PPR(r13)
+END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
+	HMT_MEDIUM
+	mfcr	r10
+	std	r12,HSTATE_SCRATCH0(r13)
+	sldi	r12,r10,32
+	ori	r12,r12,0xc00
+	ld	r10,PACA_EXGEN+EX_R10(r13)
 
 .global	kvmppc_interrupt
 .balign IFETCH_ALIGN_BYTES