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powerpc/kvm: Use UV_RETURN ucall to return to ultravisor

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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