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powerpc/kvm: Use UV_RETURN ucall to return to ultravisor 

When an SVM makes an hypercall or incurs some other exception, the
Ultravisor usually forwards (a.k.a. reflects) the exceptions to the
Hypervisor. After processing the exception, Hypervisor uses the
UV_RETURN ultracall to return control back to the SVM.

The expected register state on entry to this ultracall is:

* Non-volatile registers are restored to their original values.
* If returning from an hypercall, register R0 contains the return value
  (unlike other ultracalls) and, registers R4 through R12 contain any
  output values of the hypercall.
* R3 contains the ultracall number, i.e UV_RETURN.
* If returning with a synthesized interrupt, R2 contains the
  synthesized interrupt number.

Thanks to input from Paul Mackerras, Ram Pai and Mike Anderson.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190822034838.27876-8-cclaudio@linux.ibm.com
This commit is contained in:
Sukadev Bhattiprolu 2019-08-22 00:48:38 -03:00 committed by Michael Ellerman
parent 512a5a6452
commit 6c85b7bc63
4 changed files with 36 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/kvm_host.h
View File

@ -283,6 +283,7 @@ struct kvm_arch {
cpumask_t cpu_in_guest;
u8 radix;
u8 fwnmi_enabled;
u8 secure_guest;
bool threads_indep;
bool nested_enable;
pgd_t *pgtable;

1
arch/powerpc/include/asm/ultravisor-api.h
View File

@ -24,5 +24,6 @@
/* opcodes */
#define UV_WRITE_PATE 0xF104
#define UV_RETURN 0xF11C
#endif /* _ASM_POWERPC_ULTRAVISOR_API_H */

1
arch/powerpc/kernel/asm-offsets.c
View File

@ -506,6 +506,7 @@ int main(void)
OFFSET(KVM_VRMA_SLB_V, kvm, arch.vrma_slb_v);
OFFSET(KVM_RADIX, kvm, arch.radix);
OFFSET(KVM_FWNMI, kvm, arch.fwnmi_enabled);
OFFSET(KVM_SECURE_GUEST, kvm, arch.secure_guest);
OFFSET(VCPU_DSISR, kvm_vcpu, arch.shregs.dsisr);
OFFSET(VCPU_DAR, kvm_vcpu, arch.shregs.dar);
OFFSET(VCPU_VPA, kvm_vcpu, arch.vpa.pinned_addr);

39
arch/powerpc/kvm/book3s_hv_rmhandlers.S
View File

@ -29,6 +29,7 @@
#include <asm/asm-compat.h>
#include <asm/feature-fixups.h>
#include <asm/cpuidle.h>
#include <asm/ultravisor-api.h>
/* Sign-extend HDEC if not on POWER9 */
#define EXTEND_HDEC(reg) \
@ -1085,16 +1086,10 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
ld r5, VCPU_LR(r4)
ld r6, VCPU_CR(r4)
mtlr r5
mtcr r6
ld r1, VCPU_GPR(R1)(r4)
ld r2, VCPU_GPR(R2)(r4)
ld r3, VCPU_GPR(R3)(r4)
ld r5, VCPU_GPR(R5)(r4)
ld r6, VCPU_GPR(R6)(r4)
ld r7, VCPU_GPR(R7)(r4)
ld r8, VCPU_GPR(R8)(r4)
ld r9, VCPU_GPR(R9)(r4)
ld r10, VCPU_GPR(R10)(r4)
@ -1112,10 +1107,42 @@ BEGIN_FTR_SECTION
mtspr SPRN_HDSISR, r0
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
ld r6, VCPU_KVM(r4)
lbz r7, KVM_SECURE_GUEST(r6)
cmpdi r7, 0
ld r6, VCPU_GPR(R6)(r4)
ld r7, VCPU_GPR(R7)(r4)
bne ret_to_ultra
lwz r0, VCPU_CR(r4)
mtcr r0
ld r0, VCPU_GPR(R0)(r4)
ld r2, VCPU_GPR(R2)(r4)
ld r3, VCPU_GPR(R3)(r4)
ld r4, VCPU_GPR(R4)(r4)
HRFI_TO_GUEST
b .
/*
* Use UV_RETURN ultracall to return control back to the Ultravisor after
* processing an hypercall or interrupt that was forwarded (a.k.a. reflected)
* to the Hypervisor.
*
* All registers have already been loaded, except:
* R0 = hcall result
* R2 = SRR1, so UV can detect a synthesized interrupt (if any)
* R3 = UV_RETURN
*/
ret_to_ultra:
lwz r0, VCPU_CR(r4)
mtcr r0
ld r0, VCPU_GPR(R3)(r4)
mfspr r2, SPRN_SRR1
li r3, 0
ori r3, r3, UV_RETURN
ld r4, VCPU_GPR(R4)(r4)
sc 2
/*
* Enter the guest on a P9 or later system where we have exactly