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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
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1
arch/powerpc/include/asm/ultravisor-api.h
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@@ -24,5 +24,6 @@
/* opcodes */
#define UV_WRITE_PATE 0xF104
#define UV_RETURN 0xF11C
#endif /* _ASM_POWERPC_ULTRAVISOR_API_H */