powerpc/kernel: Add ucall_norets() ultravisor call handler

The ultracalls (ucalls for short) allow the Secure Virtual Machines
(SVM)s and hypervisor to request services from the ultravisor such as
accessing a register or memory region that can only be accessed when
running in ultravisor-privileged mode.

This patch adds the ucall_norets() ultravisor call handler.

The specific service needed from an ucall is specified in register
R3 (the first parameter to the ucall). Other parameters to the
ucall, if any, are specified in registers R4 through R12.

Return value of all ucalls is in register R3. Other output values
from the ucall, if any, are returned in registers R4 through R12.

Each ucall returns specific error codes, applicable in the context
of the ucall. However, like with the PowerPC Architecture Platform
Reference (PAPR), if no specific error code is defined for a particular
situation, then the ucall will fallback to an erroneous
parameter-position based code. i.e U_PARAMETER, U_P2, U_P3 etc depending
on the ucall parameter that may have caused the error.

Every host kernel (powernv) needs to be able to do ucalls in case it
ends up being run in a machine with ultravisor enabled. Otherwise, the
kernel may crash early in boot trying to access ultravisor resources,
for instance, trying to set the partition table entry 0. Secure guests
also need to be able to do ucalls and its kernel may not have
CONFIG_PPC_POWERNV=y. For that reason, the ucall.S file is placed under
arch/powerpc/kernel.

If ultravisor is not enabled, the ucalls will be redirected to the
hypervisor which must handle/fail the call.

Thanks to inputs from Ram Pai and Michael Anderson.

Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190822034838.27876-3-cclaudio@linux.ibm.com
This commit is contained in:
Claudio Carvalho 2019-08-22 00:48:33 -03:00 committed by Michael Ellerman
parent 250c6c3122
commit a49dddbdb0
4 changed files with 49 additions and 0 deletions

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@ -15,6 +15,7 @@
#include <asm/epapr_hcalls.h>
#include <asm/dcr.h>
#include <asm/mmu_context.h>
#include <asm/ultravisor-api.h>
#include <uapi/asm/ucontext.h>
@ -34,6 +35,16 @@ extern struct static_key hcall_tracepoint_key;
void __trace_hcall_entry(unsigned long opcode, unsigned long *args);
void __trace_hcall_exit(long opcode, long retval, unsigned long *retbuf);
/* Ultravisor */
#ifdef CONFIG_PPC_POWERNV
long ucall_norets(unsigned long opcode, ...);
#else
static inline long ucall_norets(unsigned long opcode, ...)
{
return U_NOT_AVAILABLE;
}
#endif
/* OPAL */
int64_t __opal_call(int64_t a0, int64_t a1, int64_t a2, int64_t a3,
int64_t a4, int64_t a5, int64_t a6, int64_t a7,

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@ -0,0 +1,23 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Ultravisor API.
*
* Copyright 2019, IBM Corporation.
*
*/
#ifndef _ASM_POWERPC_ULTRAVISOR_API_H
#define _ASM_POWERPC_ULTRAVISOR_API_H
#include <asm/hvcall.h>
/* Return codes */
#define U_FUNCTION H_FUNCTION
#define U_NOT_AVAILABLE H_NOT_AVAILABLE
#define U_P2 H_P2
#define U_P3 H_P3
#define U_P4 H_P4
#define U_P5 H_P5
#define U_PARAMETER H_PARAMETER
#define U_SUCCESS H_SUCCESS
#endif /* _ASM_POWERPC_ULTRAVISOR_API_H */

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@ -156,6 +156,7 @@ endif
obj-$(CONFIG_EPAPR_PARAVIRT) += epapr_paravirt.o epapr_hcalls.o
obj-$(CONFIG_KVM_GUEST) += kvm.o kvm_emul.o
obj-$(CONFIG_PPC_POWERNV) += ucall.o
# Disable GCOV, KCOV & sanitizers in odd or sensitive code
GCOV_PROFILE_prom_init.o := n

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@ -0,0 +1,14 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Generic code to perform an ultravisor call.
*
* Copyright 2019, IBM Corporation.
*
*/
#include <asm/ppc_asm.h>
#include <asm/export.h>
_GLOBAL(ucall_norets)
EXPORT_SYMBOL_GPL(ucall_norets)
sc 2 /* Invoke the ultravisor */
blr /* Return r3 = status */