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/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) 2019 Arm Ltd. */
# ifndef __KVM_ARM_HYPERCALLS_H
# define __KVM_ARM_HYPERCALLS_H
# include <asm/kvm_emulate.h>
int kvm_hvc_call_handler ( struct kvm_vcpu * vcpu ) ;
static inline u32 smccc_get_function ( struct kvm_vcpu * vcpu )
{
return vcpu_get_reg ( vcpu , 0 ) ;
}
static inline unsigned long smccc_get_arg1 ( struct kvm_vcpu * vcpu )
{
return vcpu_get_reg ( vcpu , 1 ) ;
}
static inline unsigned long smccc_get_arg2 ( struct kvm_vcpu * vcpu )
{
return vcpu_get_reg ( vcpu , 2 ) ;
}
static inline unsigned long smccc_get_arg3 ( struct kvm_vcpu * vcpu )
{
return vcpu_get_reg ( vcpu , 3 ) ;
}
static inline void smccc_set_retval ( struct kvm_vcpu * vcpu ,
unsigned long a0 ,
unsigned long a1 ,
unsigned long a2 ,
unsigned long a3 )
{
vcpu_set_reg ( vcpu , 0 , a0 ) ;
vcpu_set_reg ( vcpu , 1 , a1 ) ;
vcpu_set_reg ( vcpu , 2 , a2 ) ;
vcpu_set_reg ( vcpu , 3 , a3 ) ;
}
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struct kvm_one_reg ;
KVM: arm64: Setup a framework for hypercall bitmap firmware registers
KVM regularly introduces new hypercall services to the guests without
any consent from the userspace. This means, the guests can observe
hypercall services in and out as they migrate across various host
kernel versions. This could be a major problem if the guest
discovered a hypercall, started using it, and after getting migrated
to an older kernel realizes that it's no longer available. Depending
on how the guest handles the change, there's a potential chance that
the guest would just panic.
As a result, there's a need for the userspace to elect the services
that it wishes the guest to discover. It can elect these services
based on the kernels spread across its (migration) fleet. To remedy
this, extend the existing firmware pseudo-registers, such as
KVM_REG_ARM_PSCI_VERSION, but by creating a new COPROC register space
for all the hypercall services available.
These firmware registers are categorized based on the service call
owners, but unlike the existing firmware pseudo-registers, they hold
the features supported in the form of a bitmap.
During the VM initialization, the registers are set to upper-limit of
the features supported by the corresponding registers. It's expected
that the VMMs discover the features provided by each register via
GET_ONE_REG, and write back the desired values using SET_ONE_REG.
KVM allows this modification only until the VM has started.
Some of the standard features are not mapped to any bits of the
registers. But since they can recreate the original problem of
making it available without userspace's consent, they need to
be explicitly added to the case-list in
kvm_hvc_call_default_allowed(). Any function-id that's not enabled
via the bitmap, or not listed in kvm_hvc_call_default_allowed, will
be returned as SMCCC_RET_NOT_SUPPORTED to the guest.
Older userspace code can simply ignore the feature and the
hypercall services will be exposed unconditionally to the guests,
thus ensuring backward compatibility.
In this patch, the framework adds the register only for ARM's standard
secure services (owner value 4). Currently, this includes support only
for ARM True Random Number Generator (TRNG) service, with bit-0 of the
register representing mandatory features of v1.0. Other services are
momentarily added in the upcoming patches.
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
[maz: reduced the scope of some helpers, tidy-up bitmap max values,
dropped error-only fast path]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220502233853.1233742-3-rananta@google.com
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void kvm_arm_init_hypercalls ( struct kvm * kvm ) ;
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int kvm_arm_get_fw_num_regs ( struct kvm_vcpu * vcpu ) ;
int kvm_arm_copy_fw_reg_indices ( struct kvm_vcpu * vcpu , u64 __user * uindices ) ;
int kvm_arm_get_fw_reg ( struct kvm_vcpu * vcpu , const struct kvm_one_reg * reg ) ;
int kvm_arm_set_fw_reg ( struct kvm_vcpu * vcpu , const struct kvm_one_reg * reg ) ;
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# endif
