linux-kernel - [PATCH 1/2] KVM: x86: async_pf: remove support for KVM_ASYNC_PF_SEND

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241127172654.1024-2-kalyazin@amazon.com>
Date: Wed, 27 Nov 2024 17:26:53 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: <pbonzini@...hat.com>, <corbet@....net>, <seanjc@...gle.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
	<vkuznets@...hat.com>, <xiaoyao.li@...el.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>
CC: <roypat@...zon.co.uk>, <xmarcalx@...zon.com>, <kalyazin@...zon.com>
Subject: [PATCH 1/2] KVM: x86: async_pf: remove support for KVM_ASYNC_PF_SEND_ALWAYS

3a7c8fafd1b42adea229fd204132f6a2fb3cd2d9 ("x86/kvm: Restrict
ASYNC_PF to user space") stopped setting KVM_ASYNC_PF_SEND_ALWAYS in
Linux guests.  While the flag can still be used by legacy guests, the
mechanism is best effort so KVM is not obliged to use it.

Suggested-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 Documentation/virt/kvm/x86/msr.rst   | 11 +++++------
 arch/x86/include/asm/kvm_host.h      |  1 -
 arch/x86/include/uapi/asm/kvm_para.h |  2 +-
 arch/x86/kvm/x86.c                   |  4 +---
 4 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/Documentation/virt/kvm/x86/msr.rst b/Documentation/virt/kvm/x86/msr.rst
index 3aecf2a70e7b..b3bbc12b5d03 100644
--- a/Documentation/virt/kvm/x86/msr.rst
+++ b/Documentation/virt/kvm/x86/msr.rst
@@ -208,12 +208,11 @@ data:
 
 	Bits 5-4 of the MSR are reserved and should be zero. Bit 0 is set to 1
 	when asynchronous page faults are enabled on the vcpu, 0 when disabled.
-	Bit 1 is 1 if asynchronous page faults can be injected when vcpu is in
-	cpl == 0. Bit 2 is 1 if asynchronous page faults are delivered to L1 as
-	#PF vmexits.  Bit 2 can be set only if KVM_FEATURE_ASYNC_PF_VMEXIT is
-	present in CPUID. Bit 3 enables interrupt based delivery of 'page ready'
-	events. Bit 3 can only be set if KVM_FEATURE_ASYNC_PF_INT is present in
-	CPUID.
+	Bit 1 is reserved and should be zero. Bit 2 is 1 if asynchronous page
+	faults are delivered to L1 as #PF vmexits.  Bit 2 can be set only if
+	KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID. Bit 3 enables
+	interrupt based delivery of 'page ready' events. Bit 3 can only be set
+	if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
 
 	'Page not present' events are currently always delivered as synthetic
 	#PF exception. During delivery of these events APF CR2 register contains
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e159e44a6a1b..8ce00b17316f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -975,7 +975,6 @@ struct kvm_vcpu_arch {
 		u64 msr_int_val; /* MSR_KVM_ASYNC_PF_INT */
 		u16 vec;
 		u32 id;
-		bool send_user_only;
 		u32 host_apf_flags;
 		bool delivery_as_pf_vmexit;
 		bool pageready_pending;
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index a1efa7907a0b..5558a1ec3dc9 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -87,7 +87,7 @@ struct kvm_clock_pairing {
 #define KVM_MAX_MMU_OP_BATCH           32
 
 #define KVM_ASYNC_PF_ENABLED			(1 << 0)
-#define KVM_ASYNC_PF_SEND_ALWAYS		(1 << 1)
+#define KVM_ASYNC_PF_SEND_ALWAYS		(1 << 1) /* deprecated */
 #define KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT	(1 << 2)
 #define KVM_ASYNC_PF_DELIVERY_AS_INT		(1 << 3)
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2e713480933a..8f784f07d423 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3558,7 +3558,6 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
 					sizeof(u64)))
 		return 1;
 
-	vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
 	vcpu->arch.apf.delivery_as_pf_vmexit = data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
 
 	kvm_async_pf_wakeup_all(vcpu);
@@ -13361,8 +13360,7 @@ static bool kvm_can_deliver_async_pf(struct kvm_vcpu *vcpu)
 	if (!kvm_pv_async_pf_enabled(vcpu))
 		return false;
 
-	if (vcpu->arch.apf.send_user_only &&
-	    kvm_x86_call(get_cpl)(vcpu) == 0)
+	if (kvm_x86_call(get_cpl)(vcpu) == 0)
 		return false;
 
 	if (is_guest_mode(vcpu)) {
-- 
2.40.1