| Message ID | 20190808040555.2371-3-cclaudio@linux.ibm.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | kvmppc: Paravirtualize KVM to support ultravisor | expand |
Claudio Carvalho <cclaudio@linux.ibm.com> writes: > diff --git a/arch/powerpc/kernel/ucall.S b/arch/powerpc/kernel/ucall.S > new file mode 100644 > index 000000000000..de9133e45d21 > --- /dev/null > +++ b/arch/powerpc/kernel/ucall.S > @@ -0,0 +1,20 @@ > +/* 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) > + mfcr r0 > + stw r0,8(r1) > + > + sc 2 /* Invoke the ultravisor */ > + > + lwz r0,8(r1) > + mtcrf 0xff,r0 > + blr /* Return r3 = status */ Paulus points that we shouldn't need to save CR here. Our caller will have already saved it if it needed to, and we don't use CR in this function so we don't need to save it. That's assuming the Ultravisor follows the hcall ABI in which CR2-4 are non-volatile (PAPR § 14.5.3). I know plpar_hcall_norets() does save CR, but it shouldn't need to, that seems to be historical. aka. no one knows why it does it but it always has. cheers
On Wed, Aug 14, 2019 at 08:46:15PM +1000, Michael Ellerman wrote: > Claudio Carvalho <cclaudio@linux.ibm.com> writes: > > +_GLOBAL(ucall_norets) > > +EXPORT_SYMBOL_GPL(ucall_norets) > > + mfcr r0 > > + stw r0,8(r1) > > + > > + sc 2 /* Invoke the ultravisor */ > > + > > + lwz r0,8(r1) > > + mtcrf 0xff,r0 > > + blr /* Return r3 = status */ > > Paulus points that we shouldn't need to save CR here. Our caller will > have already saved it if it needed to, and we don't use CR in this > function so we don't need to save it. > > That's assuming the Ultravisor follows the hcall ABI in which CR2-4 are > non-volatile (PAPR § 14.5.3). And assuming the ultravisor already clears (or sets, or whatever) all CR fields it does not want to leak the contents of (which it also should, of course). > I know plpar_hcall_norets() does save CR, but it shouldn't need to, that > seems to be historical. aka. no one knows why it does it but it always > has. Segher
On 8/14/19 7:46 AM, Michael Ellerman wrote: > Claudio Carvalho <cclaudio@linux.ibm.com> writes: >> diff --git a/arch/powerpc/kernel/ucall.S b/arch/powerpc/kernel/ucall.S >> new file mode 100644 >> index 000000000000..de9133e45d21 >> --- /dev/null >> +++ b/arch/powerpc/kernel/ucall.S >> @@ -0,0 +1,20 @@ >> +/* 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) >> + mfcr r0 >> + stw r0,8(r1) >> + >> + sc 2 /* Invoke the ultravisor */ >> + >> + lwz r0,8(r1) >> + mtcrf 0xff,r0 >> + blr /* Return r3 = status */ > Paulus points that we shouldn't need to save CR here. Our caller will > have already saved it if it needed to, and we don't use CR in this > function so we don't need to save it. Dropped the CR save/restore in the next patchset version: _GLOBAL(ucall_norets) EXPORT_SYMBOL_GPL(ucall_norets) sc 2 /* Invoke the ultravisor */ blr /* Return r3 = status */ Thanks, Claudio > > That's assuming the Ultravisor follows the hcall ABI in which CR2-4 are > non-volatile (PAPR § 14.5.3). > > I know plpar_hcall_norets() does save CR, but it shouldn't need to, that > seems to be historical. aka. no one knows why it does it but it always > has. > > cheers >
On 8/14/19 3:34 PM, Segher Boessenkool wrote: > On Wed, Aug 14, 2019 at 08:46:15PM +1000, Michael Ellerman wrote: >> Claudio Carvalho <cclaudio@linux.ibm.com> writes: >>> +_GLOBAL(ucall_norets) >>> +EXPORT_SYMBOL_GPL(ucall_norets) >>> + mfcr r0 >>> + stw r0,8(r1) >>> + >>> + sc 2 /* Invoke the ultravisor */ >>> + >>> + lwz r0,8(r1) >>> + mtcrf 0xff,r0 >>> + blr /* Return r3 = status */ >> Paulus points that we shouldn't need to save CR here. Our caller will >> have already saved it if it needed to, and we don't use CR in this >> function so we don't need to save it. >> >> That's assuming the Ultravisor follows the hcall ABI in which CR2-4 are >> non-volatile (PAPR § 14.5.3). > And assuming the ultravisor already clears (or sets, or whatever) all CR > fields it does not want to leak the contents of (which it also should, > of course). Thanks Segher. We are working on that in the ultravisor source code. Claudio. > >> I know plpar_hcall_norets() does save CR, but it shouldn't need to, that >> seems to be historical. aka. no one knows why it does it but it always >> has. > > Segher >
diff --git a/arch/powerpc/include/asm/asm-prototypes.h b/arch/powerpc/include/asm/asm-prototypes.h index 296584e6dd55..ee2e67d5a005 100644 --- a/arch/powerpc/include/asm/asm-prototypes.h +++ b/arch/powerpc/include/asm/asm-prototypes.h @@ -19,6 +19,7 @@ #include <asm/epapr_hcalls.h> #include <asm/dcr.h> #include <asm/mmu_context.h> +#include <asm/ultravisor-api.h> #include <uapi/asm/ucontext.h> @@ -38,6 +39,16 @@ 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, diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h new file mode 100644 index 000000000000..88ffa78f9d61 --- /dev/null +++ b/arch/powerpc/include/asm/ultravisor-api.h @@ -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 */ diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 56dfa7a2a6f2..35379b632f3c 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -155,6 +155,7 @@ 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 diff --git a/arch/powerpc/kernel/ucall.S b/arch/powerpc/kernel/ucall.S new file mode 100644 index 000000000000..de9133e45d21 --- /dev/null +++ b/arch/powerpc/kernel/ucall.S @@ -0,0 +1,20 @@ +/* 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) + mfcr r0 + stw r0,8(r1) + + sc 2 /* Invoke the ultravisor */ + + lwz r0,8(r1) + mtcrf 0xff,r0 + blr /* Return r3 = status */
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. Like plpar_hcall_norets(), it also saves and restores the Condition Register (CR). 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> --- Ultravisor call support for secure guests is being proposed as part of the patchset "Secure Virtual Machine Enablement" posted by Thiago Bauermann. --- arch/powerpc/include/asm/asm-prototypes.h | 11 +++++++++++ arch/powerpc/include/asm/ultravisor-api.h | 23 +++++++++++++++++++++++ arch/powerpc/kernel/Makefile | 1 + arch/powerpc/kernel/ucall.S | 20 ++++++++++++++++++++ 4 files changed, 55 insertions(+) create mode 100644 arch/powerpc/include/asm/ultravisor-api.h create mode 100644 arch/powerpc/kernel/ucall.S