From: Yang Weijiang <weijiang.yang@intel.com>
To: seanjc@google.com, pbonzini@redhat.com, dave.hansen@intel.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, yuan.yao@linux.intel.com
Cc: peterz@infradead.org, chao.gao@intel.com,
rick.p.edgecombe@intel.com, mlevitsk@redhat.com,
john.allen@amd.com, weijiang.yang@intel.com
Subject: [PATCH v9 15/27] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs
Date: Tue, 23 Jan 2024 18:41:48 -0800 [thread overview]
Message-ID: <20240124024200.102792-16-weijiang.yang@intel.com> (raw)
In-Reply-To: <20240124024200.102792-1-weijiang.yang@intel.com>
From: Sean Christopherson <seanjc@google.com>
Load the guest's FPU state if userspace is accessing MSRs whose values
are managed by XSAVES. Introduce two helpers, kvm_{get,set}_xstate_msr(),
to facilitate access to such kind of MSRs.
If MSRs supported in kvm_caps.supported_xss are passed through to guest,
the guest MSRs are swapped with host's before vCPU exits to userspace and
after it reenters kernel before next VM-entry.
Because the modified code is also used for the KVM_GET_MSRS device ioctl(),
explicitly check @vcpu is non-null before attempting to load guest state.
The XSAVE-managed MSRs cannot be retrieved via the device ioctl() without
loading guest FPU state (which doesn't exist).
Note that guest_cpuid_has() is not queried as host userspace is allowed to
access MSRs that have not been exposed to the guest, e.g. it might do
KVM_SET_MSRS prior to KVM_SET_CPUID2.
The two helpers are put here in order to manifest accessing xsave-managed MSRs
requires special check and handling to guarantee the correctness of read/write
to the MSRs.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Yang Weijiang <weijiang.yang@intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/x86.c | 35 ++++++++++++++++++++++++++++++++++-
arch/x86/kvm/x86.h | 24 ++++++++++++++++++++++++
2 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f50c5a523b92..bde780ae69bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -133,6 +133,9 @@ static int __set_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2);
static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2);
static DEFINE_MUTEX(vendor_module_lock);
+static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
+static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
+
struct kvm_x86_ops kvm_x86_ops __read_mostly;
#define KVM_X86_OP(func) \
@@ -4509,6 +4512,21 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
}
EXPORT_SYMBOL_GPL(kvm_get_msr_common);
+/*
+ * Returns true if the MSR in question is managed via XSTATE, i.e. is context
+ * switched with the rest of guest FPU state.
+ */
+static bool is_xstate_managed_msr(u32 index)
+{
+ switch (index) {
+ case MSR_IA32_U_CET:
+ case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
+ return true;
+ default:
+ return false;
+ }
+}
+
/*
* Read or write a bunch of msrs. All parameters are kernel addresses.
*
@@ -4519,11 +4537,26 @@ static int __msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs *msrs,
int (*do_msr)(struct kvm_vcpu *vcpu,
unsigned index, u64 *data))
{
+ bool fpu_loaded = false;
int i;
- for (i = 0; i < msrs->nmsrs; ++i)
+ for (i = 0; i < msrs->nmsrs; ++i) {
+ /*
+ * If userspace is accessing one or more XSTATE-managed MSRs,
+ * temporarily load the guest's FPU state so that the guest's
+ * MSR value(s) is resident in hardware, i.e. so that KVM can
+ * get/set the MSR via RDMSR/WRMSR.
+ */
+ if (vcpu && !fpu_loaded && kvm_caps.supported_xss &&
+ is_xstate_managed_msr(entries[i].index)) {
+ kvm_load_guest_fpu(vcpu);
+ fpu_loaded = true;
+ }
if (do_msr(vcpu, entries[i].index, &entries[i].data))
break;
+ }
+ if (fpu_loaded)
+ kvm_put_guest_fpu(vcpu);
return i;
}
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 2f7e19166658..9c19dfb5011d 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -543,4 +543,28 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
unsigned int port, void *data, unsigned int count,
int in);
+/*
+ * Lock and/or reload guest FPU and access xstate MSRs. For accesses initiated
+ * by host, guest FPU is loaded in __msr_io(). For accesses initiated by guest,
+ * guest FPU should have been loaded already.
+ */
+
+static inline void kvm_get_xstate_msr(struct kvm_vcpu *vcpu,
+ struct msr_data *msr_info)
+{
+ KVM_BUG_ON(!vcpu->arch.guest_fpu.fpstate->in_use, vcpu->kvm);
+ kvm_fpu_get();
+ rdmsrl(msr_info->index, msr_info->data);
+ kvm_fpu_put();
+}
+
+static inline void kvm_set_xstate_msr(struct kvm_vcpu *vcpu,
+ struct msr_data *msr_info)
+{
+ KVM_BUG_ON(!vcpu->arch.guest_fpu.fpstate->in_use, vcpu->kvm);
+ kvm_fpu_get();
+ wrmsrl(msr_info->index, msr_info->data);
+ kvm_fpu_put();
+}
+
#endif
--
2.39.3
next prev parent reply other threads:[~2024-01-24 2:42 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 2:41 [PATCH v9 00/27] Enable CET Virtualization Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 01/27] x86/fpu/xstate: Always preserve non-user xfeatures/flags in __state_perm Yang Weijiang
2024-01-30 1:29 ` Edgecombe, Rick P
2024-01-24 2:41 ` [PATCH v9 02/27] x86/fpu/xstate: Refine CET user xstate bit enabling Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 03/27] x86/fpu/xstate: Add CET supervisor mode state support Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 04/27] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 05/27] x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration Yang Weijiang
2024-01-30 1:29 ` Edgecombe, Rick P
2024-01-30 15:00 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 06/27] x86/fpu/xstate: Create guest fpstate with guest specific config Yang Weijiang
2024-01-30 1:38 ` Edgecombe, Rick P
2024-01-30 14:54 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 07/27] x86/fpu/xstate: Warn if kernel dynamic xfeatures detected in normal fpstate Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 08/27] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 09/27] KVM: x86: Rename kvm_{g,s}et_msr() to menifest emulation operations Yang Weijiang
2024-01-25 3:43 ` Chao Gao
2024-01-24 2:41 ` [PATCH v9 10/27] KVM: x86: Refine xsave-managed guest register/MSR reset handling Yang Weijiang
2024-01-25 10:17 ` Chao Gao
2024-01-26 9:13 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 11/27] KVM: x86: Add kvm_msr_{read,write}() helpers Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 12/27] KVM: x86: Report XSS as to-be-saved if there are supported features Yang Weijiang
2024-01-25 10:37 ` Chao Gao
2024-01-24 2:41 ` [PATCH v9 13/27] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS Yang Weijiang
2024-01-25 10:57 ` Chao Gao
2024-01-26 9:30 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 14/27] KVM: x86: Initialize kvm_caps.supported_xss Yang Weijiang
2024-01-26 1:35 ` Chao Gao
2024-01-24 2:41 ` Yang Weijiang [this message]
2024-01-24 2:41 ` [PATCH v9 16/27] KVM: x86: Add fault checks for guest CR4.CET setting Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 17/27] KVM: x86: Report KVM supported CET MSRs as to-be-saved Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 18/27] KVM: VMX: Introduce CET VMCS fields and control bits Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 19/27] KVM: x86: Use KVM-governed feature framework to track "SHSTK/IBT enabled" Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 20/27] KVM: VMX: Emulate read and write to CET MSRs Yang Weijiang
2024-01-24 2:41 ` [PATCH v9 21/27] KVM: x86: Save and reload SSP to/from SMRAM Yang Weijiang
2024-01-26 3:17 ` Chao Gao
2024-01-26 6:51 ` Chao Gao
2024-01-24 2:41 ` [PATCH v9 22/27] KVM: VMX: Set up interception for CET MSRs Yang Weijiang
2024-01-26 3:54 ` Chao Gao
2024-01-26 9:36 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 23/27] KVM: VMX: Set host constant supervisor states to VMCS fields Yang Weijiang
2024-01-26 6:31 ` Chao Gao
2024-01-26 9:37 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 24/27] KVM: x86: Enable CET virtualization for VMX and advertise to userspace Yang Weijiang
2024-01-26 7:50 ` Chao Gao
2024-01-26 12:54 ` Yang, Weijiang
2024-01-24 2:41 ` [PATCH v9 25/27] KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery to L1 Yang Weijiang
2024-01-26 7:54 ` Chao Gao
2024-01-24 2:41 ` [PATCH v9 26/27] KVM: nVMX: Enable CET support for nested guest Yang Weijiang
2024-01-29 7:04 ` Chao Gao
2024-01-30 7:38 ` Yang, Weijiang
2024-01-24 2:42 ` [PATCH v9 27/27] KVM: x86: Stop emulating for CET protected branch instructions Yang Weijiang
2024-01-26 8:53 ` Chao Gao
2024-01-26 12:56 ` Yang, Weijiang
2024-01-30 1:40 ` [PATCH v9 00/27] Enable CET Virtualization Edgecombe, Rick P
2024-01-30 15:05 ` Yang, Weijiang
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