[PATCH v5 18/48] KVM: PPC: Book3S 64: Minimise hcall handler calling convention differences
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-04-01 15:12:10
Subsystem:
kernel virtual machine for powerpc (kvm/powerpc), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
This sets up the same calling convention from interrupt entry to KVM interrupt handler for system calls as exists for other interrupt types. This is a better API, it uses a save area rather than SPR, and it has more registers free to use. Using a single common API helps maintain it, and it becomes easier to use in C in a later patch. Reviewed-by: Alexey Kardashevskiy <redacted> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/exceptions-64s.S | 21 +++++++++++- arch/powerpc/kvm/book3s_64_entry.S | 51 +++++++++++----------------- 2 files changed, 39 insertions(+), 33 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 115cf79f3e82..4615057681c3 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S@@ -1892,8 +1892,27 @@ EXC_VIRT_END(system_call, 0x4c00, 0x100) #ifdef CONFIG_KVM_BOOK3S_64_HANDLER TRAMP_REAL_BEGIN(kvm_hcall) + std r9,PACA_EXGEN+EX_R9(r13) + std r11,PACA_EXGEN+EX_R11(r13) + std r12,PACA_EXGEN+EX_R12(r13) + mfcr r9 mfctr r10 - SET_SCRATCH0(r10) /* Save r13 in SCRATCH0 */ + std r10,PACA_EXGEN+EX_R13(r13) + li r10,0 + std r10,PACA_EXGEN+EX_CFAR(r13) + std r10,PACA_EXGEN+EX_CTR(r13) + /* + * 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,PACA_EXGEN+EX_PPR(r13) +END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) + + HMT_MEDIUM + #ifdef CONFIG_RELOCATABLE /* * Requires __LOAD_FAR_HANDLER beause kvmppc_hcall lives
diff --git a/arch/powerpc/kvm/book3s_64_entry.S b/arch/powerpc/kvm/book3s_64_entry.S
index 0791eb2e3b81..82de3e99404f 100644
--- a/arch/powerpc/kvm/book3s_64_entry.S
+++ b/arch/powerpc/kvm/book3s_64_entry.S@@ -11,40 +11,28 @@ * These are branched to from interrupt handlers in exception-64s.S which set * IKVM_REAL or IKVM_VIRT, if HSTATE_IN_GUEST was found to be non-zero. */ + +/* + * This is a hcall, so register convention is as + * Documentation/powerpc/papr_hcalls.rst. + * + * 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. + * + * The state of registers is as kvmppc_interrupt, except CFAR is not + * saved, R13 is not in SCRATCH0, and R10 does not contain the trap. + */ .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) - b do_kvm_interrupt + ld r10,PACA_EXGEN+EX_R13(r13) + SET_SCRATCH0(r10) + li r10,0xc00 + /* Now we look like kvmppc_interrupt */ /* * KVM interrupt entry occurs after GEN_INT_ENTRY runs, and follows that
@@ -91,7 +79,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ld r10,EX_R10(r11) ld r11,EX_R11(r11) -do_kvm_interrupt: /* * Hcalls and other interrupts come here after normalising register * contents and save locations:
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2.23.0