[PATCH 4/6] KVM: arm64: Add a visibility bit to ignore user writes
From: Oliver Upton <hidden>
Date: 2022-08-17 21:50:11
Also in:
kvm, kvmarm
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
We're about to ignore writes to AArch32 ID registers on AArch64-only systems. Add a bit to indicate a register is handled as write ignore when accessed from userspace. Signed-off-by: Oliver Upton <redacted> --- arch/arm64/kvm/sys_regs.c | 3 +++ arch/arm64/kvm/sys_regs.h | 7 +++++++ 2 files changed, 10 insertions(+)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 26210f3a0b27..9f06c85f26b8 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c@@ -1232,6 +1232,9 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, { bool raz = sysreg_visible_as_raz(vcpu, rd); + if (sysreg_user_write_ignore(vcpu, rd)) + return 0; + /* This is what we mean by invariant: you can't change it. */ if (val != read_id_reg(vcpu, rd, raz)) return -EINVAL;
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index e78b51059622..e4ebb3a379fd 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h@@ -86,6 +86,7 @@ struct sys_reg_desc { #define REG_HIDDEN (1 << 0) /* hidden from userspace and guest */ #define REG_RAZ (1 << 1) /* RAZ from userspace and guest */ +#define REG_USER_WI (1 << 2) /* WI from userspace only */ static __printf(2, 3) inline void print_sys_reg_msg(const struct sys_reg_params *p,
@@ -157,6 +158,12 @@ static inline bool sysreg_visible_as_raz(const struct kvm_vcpu *vcpu, return sysreg_visibility(vcpu, r) & REG_RAZ; } +static inline bool sysreg_user_write_ignore(const struct kvm_vcpu *vcpu, + const struct sys_reg_desc *r) +{ + return sysreg_visibility(vcpu, r) & REG_USER_WI; +} + static inline int cmp_sys_reg(const struct sys_reg_desc *i1, const struct sys_reg_desc *i2) {
--
2.37.1.595.g718a3a8f04-goog
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