[RFC v3 2/7] KVM: VMX: Expose IA32_PKRS MSR
From: Chenyi Qiang
Date: Thu Nov 05 2020 - 03:15:55 EST
Protection Keys for Supervisor Pages (PKS) uses IA32_PKRS MSR (PKRS) at
index 0x6E1 to allow software to manage supervisor protection key
rights. For performance consideration, PKRS intercept will be disabled
so that the guest can access the PKRS without VM exits.
PKS introduces dedicated control fields in VMCS to switch PKRS, which
only does the retore part. In addition, every VM exit saves PKRS into
the guest-state area in VMCS, while VM enter won't save the host value
due to the expectation that the host won't change the MSR often. Update
the host's value in VMCS manually if the MSR has been changed by the
kernel since the last time the VMCS was run.
The function get_current_pkrs() in arch/x86/mm/pkeys.c exports the
per-cpu variable pkrs_cache to avoid frequent rdmsr of PKRS.
Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
---
arch/x86/include/asm/pkeys.h | 1 +
arch/x86/kvm/vmx/capabilities.h | 6 +++
arch/x86/kvm/vmx/nested.c | 1 +
arch/x86/kvm/vmx/vmcs.h | 1 +
arch/x86/kvm/vmx/vmx.c | 66 ++++++++++++++++++++++++++++++++-
arch/x86/kvm/vmx/vmx.h | 2 +-
arch/x86/kvm/x86.h | 6 +++
arch/x86/mm/pkeys.c | 6 +++
include/linux/pkeys.h | 4 ++
9 files changed, 90 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index f84351b4ac7c..4cc5ed49ae75 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -142,6 +142,7 @@ u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags);
#ifdef CONFIG_ARCH_HAS_SUPERVISOR_PKEYS
int pks_key_alloc(const char *const pkey_user, int flags);
void pks_key_free(int pkey);
+u32 get_current_pkrs(void);
void pks_mk_noaccess(int pkey);
void pks_mk_readonly(int pkey);
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 3a1861403d73..1cadeaaf9985 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -103,6 +103,12 @@ static inline bool cpu_has_load_perf_global_ctrl(void)
(vmcs_config.vmexit_ctrl & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL);
}
+static inline bool cpu_has_load_ia32_pkrs(void)
+{
+ return (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PKRS) &&
+ (vmcs_config.vmexit_ctrl & VM_EXIT_LOAD_IA32_PKRS);
+}
+
static inline bool cpu_has_vmx_mpx(void)
{
return (vmcs_config.vmexit_ctrl & VM_EXIT_CLEAR_BNDCFGS) &&
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 89af692deb7e..2266d98ace6f 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -250,6 +250,7 @@ static void vmx_sync_vmcs_host_state(struct vcpu_vmx *vmx,
dest->ds_sel = src->ds_sel;
dest->es_sel = src->es_sel;
#endif
+ dest->pkrs = src->pkrs;
}
static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
diff --git a/arch/x86/kvm/vmx/vmcs.h b/arch/x86/kvm/vmx/vmcs.h
index 1472c6c376f7..b5ba6407c5e1 100644
--- a/arch/x86/kvm/vmx/vmcs.h
+++ b/arch/x86/kvm/vmx/vmcs.h
@@ -40,6 +40,7 @@ struct vmcs_host_state {
#ifdef CONFIG_X86_64
u16 ds_sel, es_sel;
#endif
+ u32 pkrs;
};
struct vmcs_controls_shadow {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 47b8357b9751..e18fdd8ee36a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -166,6 +166,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = {
MSR_CORE_C3_RESIDENCY,
MSR_CORE_C6_RESIDENCY,
MSR_CORE_C7_RESIDENCY,
+ MSR_IA32_PKRS,
};
/*
@@ -1201,6 +1202,7 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
#endif
unsigned long fs_base, gs_base;
u16 fs_sel, gs_sel;
+ u32 host_pkrs;
int i;
vmx->req_immediate_exit = false;
@@ -1233,6 +1235,20 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
*/
host_state->ldt_sel = kvm_read_ldt();
+ /*
+ * Update the host pkrs vmcs field before vcpu runs.
+ * The setting of VM_EXIT_LOAD_IA32_PKRS can ensure
+ * kvm_cpu_cap_has(X86_FEATURE_PKS) &&
+ * guest_cpuid_has(vcpu, X86_FEATURE_VMX).
+ */
+ if (vm_exit_controls_get(vmx) & VM_EXIT_LOAD_IA32_PKRS) {
+ host_pkrs = get_current_pkrs();
+ if (unlikely(host_pkrs != host_state->pkrs)) {
+ vmcs_write64(HOST_IA32_PKRS, host_pkrs);
+ host_state->pkrs = host_pkrs;
+ }
+ }
+
#ifdef CONFIG_X86_64
savesegment(ds, host_state->ds_sel);
savesegment(es, host_state->es_sel);
@@ -1920,6 +1936,13 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
else
msr_info->data = vmx->pt_desc.guest.addr_a[index / 2];
break;
+ case MSR_IA32_PKRS:
+ if (!kvm_cpu_cap_has(X86_FEATURE_PKS) ||
+ (!msr_info->host_initiated &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_PKS)))
+ return 1;
+ msr_info->data = vmcs_read64(GUEST_IA32_PKRS);
+ break;
case MSR_TSC_AUX:
if (!msr_info->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
@@ -2189,6 +2212,15 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
else
vmx->pt_desc.guest.addr_a[index / 2] = data;
break;
+ case MSR_IA32_PKRS:
+ if (!kvm_pkrs_valid(data))
+ return 1;
+ if (!kvm_cpu_cap_has(X86_FEATURE_PKS) ||
+ (!msr_info->host_initiated &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_PKS)))
+ return 1;
+ vmcs_write64(GUEST_IA32_PKRS, data);
+ break;
case MSR_TSC_AUX:
if (!msr_info->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
@@ -2479,7 +2511,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_EXIT_LOAD_IA32_EFER |
VM_EXIT_CLEAR_BNDCFGS |
VM_EXIT_PT_CONCEAL_PIP |
- VM_EXIT_CLEAR_IA32_RTIT_CTL;
+ VM_EXIT_CLEAR_IA32_RTIT_CTL |
+ VM_EXIT_LOAD_IA32_PKRS;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
&_vmexit_control) < 0)
return -EIO;
@@ -2503,7 +2536,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_ENTRY_LOAD_IA32_EFER |
VM_ENTRY_LOAD_BNDCFGS |
VM_ENTRY_PT_CONCEAL_PIP |
- VM_ENTRY_LOAD_IA32_RTIT_CTL;
+ VM_ENTRY_LOAD_IA32_RTIT_CTL |
+ VM_ENTRY_LOAD_IA32_PKRS;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_ENTRY_CTLS,
&_vmentry_control) < 0)
return -EIO;
@@ -5841,6 +5875,8 @@ void dump_vmcs(void)
vmcs_read64(GUEST_IA32_PERF_GLOBAL_CTRL));
if (vmentry_ctl & VM_ENTRY_LOAD_BNDCFGS)
pr_err("BndCfgS = 0x%016llx\n", vmcs_read64(GUEST_BNDCFGS));
+ if (vmentry_ctl & VM_ENTRY_LOAD_IA32_PKRS)
+ pr_err("PKRS = 0x%016llx\n", vmcs_read64(GUEST_IA32_PKRS));
pr_err("Interruptibility = %08x ActivityState = %08x\n",
vmcs_read32(GUEST_INTERRUPTIBILITY_INFO),
vmcs_read32(GUEST_ACTIVITY_STATE));
@@ -5876,6 +5912,8 @@ void dump_vmcs(void)
vmexit_ctl & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
pr_err("PerfGlobCtl = 0x%016llx\n",
vmcs_read64(HOST_IA32_PERF_GLOBAL_CTRL));
+ if (vmexit_ctl & VM_EXIT_LOAD_IA32_PKRS)
+ pr_err("PKRS = 0x%016llx\n", vmcs_read64(HOST_IA32_PKRS));
pr_err("*** Control State ***\n");
pr_err("PinBased=%08x CPUBased=%08x SecondaryExec=%08x\n",
@@ -7219,6 +7257,25 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
}
+static void vmx_update_pkrs_cfg(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ bool pks_supported = guest_cpuid_has(vcpu, X86_FEATURE_PKS);
+
+ /*
+ * set intercept for PKRS when the guest doesn't support pks
+ */
+ vmx_set_intercept_for_msr(vcpu, MSR_IA32_PKRS, MSR_TYPE_RW, !pks_supported);
+
+ if (pks_supported) {
+ vm_entry_controls_setbit(vmx, VM_ENTRY_LOAD_IA32_PKRS);
+ vm_exit_controls_setbit(vmx, VM_EXIT_LOAD_IA32_PKRS);
+ } else {
+ vm_entry_controls_clearbit(vmx, VM_ENTRY_LOAD_IA32_PKRS);
+ vm_exit_controls_clearbit(vmx, VM_EXIT_LOAD_IA32_PKRS);
+ }
+}
+
static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -7240,6 +7297,11 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
~(FEAT_CTL_VMX_ENABLED_INSIDE_SMX |
FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX);
+ if (kvm_cpu_cap_has(X86_FEATURE_PKS))
+ vmx_update_pkrs_cfg(vcpu);
+ else
+ guest_cpuid_clear(vcpu, X86_FEATURE_PKS);
+
if (nested_vmx_allowed(vcpu)) {
nested_vmx_cr_fixed1_bits_update(vcpu);
nested_vmx_entry_exit_ctls_update(vcpu);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index f6f66e5c6510..1912710e5a6f 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -281,7 +281,7 @@ struct vcpu_vmx {
struct pt_desc pt_desc;
/* Save desired MSR intercept (read: pass-through) state */
-#define MAX_POSSIBLE_PASSTHROUGH_MSRS 13
+#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14
struct {
DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 3900ab0c6004..b6eee487fd8e 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -366,6 +366,12 @@ static inline bool kvm_dr6_valid(u64 data)
return !(data >> 32);
}
+static inline bool kvm_pkrs_valid(u64 data)
+{
+ /* bit[63,32] must be zero */
+ return !(data >> 32);
+}
+
void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
int kvm_spec_ctrl_test_value(u64 value);
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 39ec034cf379..2a4878e746a3 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -388,3 +388,9 @@ void pks_key_free(int pkey)
__clear_bit(pkey, &pks_key_allocation_map);
}
EXPORT_SYMBOL_GPL(pks_key_free);
+
+u32 get_current_pkrs(void)
+{
+ return this_cpu_read(pkrs_cache);
+}
+EXPORT_SYMBOL_GPL(get_current_pkrs);
diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h
index 0959a4c0ca64..84b3ecd11bff 100644
--- a/include/linux/pkeys.h
+++ b/include/linux/pkeys.h
@@ -72,6 +72,10 @@ static inline void pks_mk_readwrite(int pkey)
{
WARN_ON_ONCE(1);
}
+static inline u32 get_current_pkrs(void)
+{
+ return 0;
+}
#endif /* ! CONFIG_ARCH_HAS_SUPERVISOR_PKEYS */
#endif /* _LINUX_PKEYS_H */
--
2.17.1