linux-kernel - [PATCH 07/19] kvm: x86: Propagate fpstate reallocation error to userspace

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Message-Id: <20211208000359.2853257-8-yang.zhong@intel.com>
Date:   Tue,  7 Dec 2021 19:03:47 -0500
From:   Yang Zhong <yang.zhong@...el.com>
To:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, pbonzini@...hat.com
Cc:     seanjc@...gle.com, jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, jing2.liu@...el.com,
        yang.zhong@...el.com
Subject: [PATCH 07/19] kvm: x86: Propagate fpstate reallocation error to userspace

From: Jing Liu <jing2.liu@...el.com>

fpstate reallocation is handled when the vCPU thread returns
to userspace. As reallocation could fail (e.g. lack of memory),
this patch extends kvm_put_guest_fpu() to return an integer value
to carry error code to userspace VMM. The userspace VMM is expected
to handle any error caused by fpstate reallocation.

Signed-off-by: Jing Liu <jing2.liu@...el.com>
Signed-off-by: Yang Zhong <yang.zhong@...el.com>
---
 arch/x86/kvm/x86.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0ee1a039b490..05f2cda73d69 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10171,17 +10171,21 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 }
 
 /* When vcpu_run ends, restore user space FPU context. */
-static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
+static int kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 {
-	fpu_swap_kvm_fpstate(&vcpu->arch.guest_fpu, false);
+	int ret;
+
+	ret = fpu_swap_kvm_fpstate(&vcpu->arch.guest_fpu, false);
 	++vcpu->stat.fpu_reload;
 	trace_kvm_fpu(0);
+
+	return ret;
 }
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
 	struct kvm_run *kvm_run = vcpu->run;
-	int r;
+	int r, ret;
 
 	vcpu_load(vcpu);
 	kvm_sigset_activate(vcpu);
@@ -10243,7 +10247,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		r = vcpu_run(vcpu);
 
 out:
-	kvm_put_guest_fpu(vcpu);
+	ret = kvm_put_guest_fpu(vcpu);
+	if ((r >= 0) && (ret < 0))
+		r = ret;
+
 	if (kvm_run->kvm_valid_regs)
 		store_regs(vcpu);
 	post_kvm_run_save(vcpu);