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Message-Id: <20240611123655.4169939-1-maobibo@loongson.cn>
Date: Tue, 11 Jun 2024 20:36:55 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>
Cc: kvm@...r.kernel.org,
loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH v2] LoongArch: KVM: Implement feature passing from user space
Currently features defined in cpucfg CPUCFG_KVM_FEATURE come from
kvm kernel mode only. However KVM is not aware of user-space VMM
features which makes it hard to employ optimizations. Here interface
is added to update register CPUCFG_KVM_FEATURE from user space,
only bit 24 - 31 is valid, so that VM can detect features implemented
in user-space VMM.
A new feature bit KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI is added which
can be set from user space. This feature indicates that the virt EXTIOI
can route interrupts to 256 vCPUs, rather than 4 vCPUs like with real HW.
Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
v1 ... v2:
1. Update changelog suggested by WangXuerui.
2. Fix typo issue in function kvm_loongarch_cpucfg_set_attr(), usr_features
should be assigned directly, also suggested by WangXueRui.
---
arch/loongarch/include/asm/kvm_host.h | 4 +++
arch/loongarch/include/asm/loongarch.h | 5 ++++
arch/loongarch/include/uapi/asm/kvm.h | 2 ++
arch/loongarch/kvm/exit.c | 1 +
arch/loongarch/kvm/vcpu.c | 36 +++++++++++++++++++++++---
5 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
index 88023ab59486..8fa50d757247 100644
--- a/arch/loongarch/include/asm/kvm_host.h
+++ b/arch/loongarch/include/asm/kvm_host.h
@@ -135,6 +135,9 @@ enum emulation_result {
#define KVM_LARCH_HWCSR_USABLE (0x1 << 4)
#define KVM_LARCH_LBT (0x1 << 5)
+#define KVM_LOONGARCH_USR_FEAT_MASK \
+ BIT(KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI)
+
struct kvm_vcpu_arch {
/*
* Switch pointer-to-function type to unsigned long
@@ -210,6 +213,7 @@ struct kvm_vcpu_arch {
u64 last_steal;
struct gfn_to_hva_cache cache;
} st;
+ unsigned int usr_features;
};
static inline unsigned long readl_sw_gcsr(struct loongarch_csrs *csr, int reg)
diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index 7a4633ef284b..4d9837512c19 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -167,9 +167,14 @@
#define CPUCFG_KVM_SIG (CPUCFG_KVM_BASE + 0)
#define KVM_SIGNATURE "KVM\0"
+/*
+ * BIT 24 - 31 is features configurable by user space vmm
+ */
#define CPUCFG_KVM_FEATURE (CPUCFG_KVM_BASE + 4)
#define KVM_FEATURE_IPI BIT(1)
#define KVM_FEATURE_STEAL_TIME BIT(2)
+/* With VIRT_EXTIOI feature, interrupt can route to 256 VCPUs */
+#define KVM_FEATURE_VIRT_EXTIOI BIT(24)
#ifndef __ASSEMBLY__
diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
index ed12e509815c..dd141259de48 100644
--- a/arch/loongarch/include/uapi/asm/kvm.h
+++ b/arch/loongarch/include/uapi/asm/kvm.h
@@ -99,6 +99,8 @@ struct kvm_fpu {
/* Device Control API on vcpu fd */
#define KVM_LOONGARCH_VCPU_CPUCFG 0
+/* For CPUCFG_KVM_FEATURE register */
+#define KVM_LOONGARCH_VCPU_FEAT_VIRT_EXTIOI 24
#define KVM_LOONGARCH_VCPU_PVTIME_CTRL 1
#define KVM_LOONGARCH_VCPU_PVTIME_GPA 0
diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index e1bd81d27fd8..ab2dcc76784a 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -53,6 +53,7 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
ret = KVM_FEATURE_IPI;
if (sched_info_on())
ret |= KVM_FEATURE_STEAL_TIME;
+ ret |= vcpu->arch.usr_features;
vcpu->arch.gprs[rd] = ret;
break;
default:
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index 3783151fde32..4a06a9e96e4e 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -832,6 +832,8 @@ static int kvm_loongarch_cpucfg_has_attr(struct kvm_vcpu *vcpu,
switch (attr->attr) {
case 2:
return 0;
+ case CPUCFG_KVM_FEATURE:
+ return 0;
default:
return -ENXIO;
}
@@ -865,9 +867,18 @@ static int kvm_loongarch_get_cpucfg_attr(struct kvm_vcpu *vcpu,
uint64_t val;
uint64_t __user *uaddr = (uint64_t __user *)attr->addr;
- ret = _kvm_get_cpucfg_mask(attr->attr, &val);
- if (ret)
- return ret;
+ switch (attr->attr) {
+ case 0 ... (KVM_MAX_CPUCFG_REGS - 1):
+ ret = _kvm_get_cpucfg_mask(attr->attr, &val);
+ if (ret)
+ return ret;
+ break;
+ case CPUCFG_KVM_FEATURE:
+ val = vcpu->arch.usr_features & KVM_LOONGARCH_USR_FEAT_MASK;
+ break;
+ default:
+ return -ENXIO;
+ }
put_user(val, uaddr);
@@ -896,7 +907,24 @@ static int kvm_loongarch_vcpu_get_attr(struct kvm_vcpu *vcpu,
static int kvm_loongarch_cpucfg_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr)
{
- return -ENXIO;
+ u64 __user *user = (u64 __user *)attr->addr;
+ u64 val, valid_flags;
+
+ switch (attr->attr) {
+ case CPUCFG_KVM_FEATURE:
+ if (get_user(val, user))
+ return -EFAULT;
+
+ valid_flags = KVM_LOONGARCH_USR_FEAT_MASK;
+ if (val & ~valid_flags)
+ return -EINVAL;
+
+ vcpu->arch.usr_features = val;
+ return 0;
+
+ default:
+ return -ENXIO;
+ }
}
static int kvm_loongarch_vcpu_set_attr(struct kvm_vcpu *vcpu,
base-commit: 2df0193e62cf887f373995fb8a91068562784adc
--
2.39.3
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