Re: [PATCH AUTOSEL for 4.14 12/67] KVM: x86: add support for emulating UMIP

----- Original Message -----

From: "Sasha Levin" Alexander.Levin@microsoft.com To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paolo Bonzini" pbonzini@redhat.com, "Sasha Levin" Alexander.Levin@microsoft.com Sent: Thursday, March 8, 2018 5:57:36 AM Subject: [PATCH AUTOSEL for 4.14 12/67] KVM: x86: add support for emulating UMIP

From: Paolo Bonzini pbonzini@redhat.com

[ Upstream commit 66336cab3531d3325ebde36a04725dddd0c42cb5 ]

The User-Mode Instruction Prevention feature present in recent Intel processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and str) from being executed with CPL > 0. Otherwise, a general protection fault is issued.

UMIP instructions in general are also able to trigger vmexits, so we can actually emulate UMIP on older processors. This commit sets up the infrastructure so that kvm-intel.ko and kvm-amd.ko can set the UMIP feature bit for CPUID even if the feature is not actually available in hardware.

Reviewed-by: Wanpeng Li wanpeng.li@hotmail.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com

This is not enough (there were a couple bugs, plus you have not added the changes needed to the handle SLDT, STR, etc. in the emulator). But since this is a feature, why is it being backported to 4.14, especially without any testing??

Thanks,

Paolo

---

arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 2 ++ arch/x86/kvm/svm.c | 6 ++++++ arch/x86/kvm/vmx.c | 6 ++++++ 4 files changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 4f8b80199672..52ecf9b2f61e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1004,6 +1004,7 @@ struct kvm_x86_ops { void (*handle_external_intr)(struct kvm_vcpu *vcpu); bool (*mpx_supported)(void); bool (*xsaves_supported)(void);

• bool (*umip_emulated)(void);

int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr); diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 13f5d4217e4f..f3fc225f5ebb 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -325,6 +325,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0; unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0; unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;

• unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0;

/* cpuid 1.edx */ const u32 kvm_cpuid_1_edx_x86_features = @@ -476,6 +477,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, entry->ebx |= F(TSC_ADJUST); entry->ecx &= kvm_cpuid_7_0_ecx_x86_features; cpuid_mask(&entry->ecx, CPUID_7_ECX);

• 	entry->ecx |= f_umip;
  /* PKU is not yet implemented for shadow paging. */
  if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
  	entry->ecx &= ~F(PKU);
  

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index e0bc3ad0f6cd..8ea19bf09202 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5322,6 +5322,11 @@ static bool svm_xsaves_supported(void) return false; } +static bool svm_umip_emulated(void) +{

• return false;

+}

static bool svm_has_wbinvd_exit(void) { return true; @@ -5633,6 +5638,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = { .invpcid_supported = svm_invpcid_supported, .mpx_supported = svm_mpx_supported, .xsaves_supported = svm_xsaves_supported,

• .umip_emulated = svm_umip_emulated,

.set_supported_cpuid = svm_set_supported_cpuid, diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 5ffde16253cb..924d88d5ca35 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -9212,6 +9212,11 @@ static bool vmx_xsaves_supported(void) SECONDARY_EXEC_XSAVES; } +static bool vmx_umip_emulated(void) +{

• return false;

+}

static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx) { u32 exit_intr_info; @@ -12252,6 +12257,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = { .handle_external_intr = vmx_handle_external_intr, .mpx_supported = vmx_mpx_supported, .xsaves_supported = vmx_xsaves_supported,

• .umip_emulated = vmx_umip_emulated,

.check_nested_events = vmx_check_nested_events, -- 2.14.1