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KVM: arm64: Save ID registers' sanitized value per guest

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Initialize the default ID register values upon the first call to
KVM_ARM_VCPU_INIT. The vCPU feature flags are finalized at that point,
so it is possible to determine the maximum feature set supported by a
particular VM configuration. Do nothing with these values for now, as we
need to rework the plumbing of what's already writable to be compatible
with the generic infrastructure.

Co-developed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Link: https://lore.kernel.org/r/20230609190054.1542113-7-oliver.upton@linux.dev
[Oliver: Hoist everything into KVM_ARM_VCPU_INIT time, so the features
 are final]
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Jing Zhang 2023-06-09 19:00:49 +00:00 committed by Oliver Upton
parent d86cde6e33
commit 4733414690
3 changed files with 75 additions and 3 deletions
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15
arch/arm64/include/asm/kvm_host.h
View File

@ -225,6 +225,8 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_TIMER_PPIS_IMMUTABLE 6
/* SMCCC filter initialized for the VM */
#define KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED 7
/* Initial ID reg values loaded */
#define KVM_ARCH_FLAG_ID_REGS_INITIALIZED 8
unsigned long flags;
/* VM-wide vCPU feature set */
@ -247,6 +249,19 @@ struct kvm_arch {
struct kvm_smccc_features smccc_feat;
struct maple_tree smccc_filter;
/*
* Emulated CPU ID registers per VM
* (Op0, Op1, CRn, CRm, Op2) of the ID registers to be saved in it
* is (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
*
* These emulated idregs are VM-wide, but accessed from the context of a vCPU.
* Atomic access to multiple idregs are guarded by kvm_arch.config_lock.
*/
#define IDREG_IDX(id) (((sys_reg_CRm(id) - 1) << 3) | sys_reg_Op2(id))
#define IDREG(kvm, id) ((kvm)->arch.id_regs[IDREG_IDX(id)])
#define KVM_ARM_ID_REG_NUM (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1)
u64 id_regs[KVM_ARM_ID_REG_NUM];
/*
* For an untrusted host VM, 'pkvm.handle' is used to lookup
* the associated pKVM instance in the hypervisor.

56
arch/arm64/kvm/sys_regs.c
View File

@ -1311,6 +1311,17 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
return __kvm_read_sanitised_id_reg(vcpu, r);
}
/*
* Return true if the register's (Op0, Op1, CRn, CRm, Op2) is
* (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
*/
static inline bool is_id_reg(u32 id)
{
return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 &&
sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 &&
sys_reg_CRm(id) < 8);
}
static unsigned int id_visibility(const struct kvm_vcpu *vcpu,
const struct sys_reg_desc *r)
{
@ -2303,6 +2314,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
EL2_REG(SP_EL2, NULL, reset_unknown, 0),
};
static const struct sys_reg_desc *first_idreg;
static bool trap_dbgdidr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
@ -2993,6 +3006,28 @@ static bool emulate_sys_reg(struct kvm_vcpu *vcpu,
return false;
}
static void kvm_reset_id_regs(struct kvm_vcpu *vcpu)
{
const struct sys_reg_desc *idreg = first_idreg;
u32 id = reg_to_encoding(idreg);
struct kvm *kvm = vcpu->kvm;
if (test_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags))
return;
lockdep_assert_held(&kvm->arch.config_lock);
/* Initialize all idregs */
while (is_id_reg(id)) {
IDREG(kvm, id) = idreg->reset(vcpu, idreg);
idreg++;
id = reg_to_encoding(idreg);
}
set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags);
}
/**
* kvm_reset_sys_regs - sets system registers to reset value
* @vcpu: The VCPU pointer
@ -3004,9 +3039,17 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
{
unsigned long i;
for (i = 0; i < ARRAY_SIZE(sys_reg_descs); i++)
if (sys_reg_descs[i].reset)
sys_reg_descs[i].reset(vcpu, &sys_reg_descs[i]);
kvm_reset_id_regs(vcpu);
for (i = 0; i < ARRAY_SIZE(sys_reg_descs); i++) {
const struct sys_reg_desc *r = &sys_reg_descs[i];
if (is_id_reg(reg_to_encoding(r)))
continue;
if (r->reset)
r->reset(vcpu, r);
}
}
/**
@ -3413,6 +3456,7 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
int __init kvm_sys_reg_table_init(void)
{
struct sys_reg_params params;
bool valid = true;
unsigned int i;
@ -3431,5 +3475,11 @@ int __init kvm_sys_reg_table_init(void)
for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)
invariant_sys_regs[i].reset(NULL, &invariant_sys_regs[i]);
/* Find the first idreg (SYS_ID_PFR0_EL1) in sys_reg_descs. */
params = encoding_to_params(SYS_ID_PFR0_EL1);
first_idreg = find_reg(&params, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
if (!first_idreg)
return -EINVAL;
return 0;
}

7
arch/arm64/kvm/sys_regs.h
View File

@ -27,6 +27,13 @@ struct sys_reg_params {
bool is_write;
};
#define encoding_to_params(reg) \
((struct sys_reg_params){ .Op0 = sys_reg_Op0(reg), \
.Op1 = sys_reg_Op1(reg), \
.CRn = sys_reg_CRn(reg), \
.CRm = sys_reg_CRm(reg), \
.Op2 = sys_reg_Op2(reg) })
#define esr_sys64_to_params(esr) \
((struct sys_reg_params){ .Op0 = ((esr) >> 20) & 3, \
.Op1 = ((esr) >> 14) & 0x7, \