KVM: PPC: Book3S 64: Move hcall early register setup to KVM

System calls / hcalls have a different calling convention than
other interrupts, so there is code in the KVMTEST to massage these
into the same form as other interrupt handlers.

Move this work into the KVM hcall handler. This means teaching KVM
a little more about the low level interrupt handler setup, PACA save
areas, etc., although that's not obviously worse than the current
approach of coming up with an entirely different interrupt register
/ save convention.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-5-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index c1a8aac01cf91d2917e923044cef69886f6eb367..bb6f78fcf981cc9a88f37a6232558412a9132ba4 100644 (file)
--- 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 4819bf60324c6db7b91cb46faefe65f5dfb22538..03e2d65d3d3f9af6c2457d01194cca29c19e7aa4 100644 (file)
--- 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 c21fa64059ef6cffa25c4bea58973e7cc7c11e65..f527e16707db1effd85548f739778e8fbd9ec6e6 100644 (file)
--- 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