From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1FDF647606A for ; Wed, 22 Jul 2026 07:44:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784706265; cv=none; b=JJkasW9grtWNECQGtwoZTKqFZdf/htkrr2rmdzsRYSCYz0G3JMhM/Auu8ToAUAb/zMq7HkyQnnbvbN5gDCpNQT1WElIV6wutmpUX8oDFz8j6KbWCsV3lEZ9SupuXqxlXKIBzaM37MmRH7w/RGbbpgZTYSmAtTVNOoqGpFb+kjL0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784706265; c=relaxed/simple; bh=FPrvqleZZkxly92bR/CLY5uc81tEF64gprLeaxY5lPQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ofcNk1jiDgoHIQXa1nQ0x7JF6DtwzS581wP6Iiwa5NgC5H2iVZ76Rw6fRM6M/cDLdYYn7SbazIWc57oUKI2HAN99PocQB5zNk4z+/XYawdj9u86jxP63I70kZnIASQYUSnjU6HroLMZm4Ns9swZyitzhR+ygfWEJVnMbslS26JU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=sb+Rxirg; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="sb+Rxirg" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784706249; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=sG2NOsOTZ2REpCl2D4kAYmK3b1M/9AA8FLqbpmvwIek=; b=sb+RxirgFN/teVJcTc5OMKD1ZKz8l6zXaic1PhVwBC8hgdoZiOUeenHQf+nWhBI9ezgTBL 2U88JqJ/d9h7WRqVu/liHNVF6w2C8qCB1GxXT68rjgjg3Pe+XMJgeSt2FcNisdaADL93ij 56y8QY2deor8dlGB0aft/o1rrfnum0Y= From: Tao Cui To: zhaotianrui@loongson.cn, maobibo@loongson.cn Cc: chenhuacai@kernel.org, kernel@xen0n.name, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, cui.tao@linux.dev, cuitao@kylinos.cn Subject: [PATCH v2] LoongArch: KVM: Add KVM_LOONGARCH_GET/SET_CSR for bulk CSR migration Date: Wed, 22 Jul 2026 15:43:46 +0800 Message-ID: <20260722074346.239507-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tao Cui Migrating a vCPU's CSR state takes one KVM_GET/SET_ONE_REG ioctl per register, thousands of syscalls for a large VM. Add a bulk pair, KVM_LOONGARCH_GET_CSR / KVM_SET_CSR. Userspace passes an array of {index, data} entries; the kernel fills entries[].data on GET and applies them on SET, both in a single call: - KVM_LOONGARCH_GET_CSR does a single vcpu_load/put with kvm_deliver_intr(), which pulls pending interrupts into ESTAT, avoiding the per-register load/put side-effect that made ONE_REG snapshots of ESTAT order-sensitive. - KVM_LOONGARCH_SET_CSR writes all CSRs via _kvm_setcsr in one pass, propagates _kvm_setcsr errors, and clears KVM_LARCH_HWCSR_USABLE up front so a mid-loop failure still forces the next vcpu_load() to reload from SW, matching KVM_SET_ONE_REG. Entries are {index, data} rather than a positional array, so future CSRs can be added without resizing the struct or changing the ioctl number. CSRs above the core range (debug, breakpoint, PMU) stay on KVM_GET/SET_ONE_REG; struct kvm_sregs is left empty, so the new ioctls break no userspace. On a Loongson 3A6000, snapshotting one vCPU's core CSR range (0x0-0x183) drops from 388 KVM_GET_ONE_REG calls (~2 ms) to a single KVM_LOONGARCH_GET_CSR ioctl (~6 us). Signed-off-by: Tao Cui --- arch/loongarch/include/uapi/asm/kvm.h | 13 +++++ arch/loongarch/kvm/vcpu.c | 73 +++++++++++++++++++++++++++ include/uapi/linux/kvm.h | 4 ++ 3 files changed, 90 insertions(+) diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h index cd0b5c11ca9c..59b3b7efa039 100644 --- a/arch/loongarch/include/uapi/asm/kvm.h +++ b/arch/loongarch/include/uapi/asm/kvm.h @@ -127,6 +127,19 @@ struct kvm_sync_regs { struct kvm_sregs { }; +/* bulk CSR entries for VM migration */ +struct kvm_loongarch_csr_entry { + __u32 index; + __u32 reserved; + __u64 data; +}; + +struct kvm_loongarch_csrs { + __u32 ncsrs; /* number of csr entries */ + __u32 pad; + __DECLARE_FLEX_ARRAY(struct kvm_loongarch_csr_entry, entries); +}; + struct kvm_iocsr_entry { __u32 addr; __u32 pad; diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c index 20c207d80e31..9b411c694718 100644 --- a/arch/loongarch/kvm/vcpu.c +++ b/arch/loongarch/kvm/vcpu.c @@ -1009,6 +1009,73 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs return -ENOIOCTLCMD; } +/* max CSR entries handled per ioctl */ +#define KVM_LOONGARCH_MAX_CSR_REGS 0x400 + +/* Bulk get/set of CSR state for VM migration. */ +static int kvm_loongarch_csr_io(struct kvm_vcpu *vcpu, + struct kvm_loongarch_csrs __user *ucsrs, + bool write) +{ + int i, ret = 0; + unsigned long size; + struct kvm_loongarch_csrs csrs; + struct kvm_loongarch_csr_entry *entries; + struct loongarch_csrs *csr = vcpu->arch.csr; + + if (copy_from_user(&csrs, ucsrs, sizeof(csrs))) + return -EFAULT; + + if (csrs.ncsrs > KVM_LOONGARCH_MAX_CSR_REGS) + return -E2BIG; + + size = array_size(csrs.ncsrs, sizeof(*entries)); + entries = memdup_user(ucsrs->entries, size); + if (IS_ERR(entries)) + return PTR_ERR(entries); + + if (write) { + vcpu->arch.aux_inuse &= ~KVM_LARCH_HWCSR_USABLE; + } else { + preempt_disable(); + vcpu_load(vcpu); + kvm_deliver_intr(vcpu); + vcpu->arch.aux_inuse &= ~KVM_LARCH_SWCSR_LATEST; + vcpu_put(vcpu); + preempt_enable(); + } + + for (i = 0; i < csrs.ncsrs; i++) { + unsigned int id = entries[i].index; + + if (get_gcsr_flag(id) & INVALID_GCSR) { + ret = -EINVAL; + break; + } + + if (write) { + ret = _kvm_setcsr(vcpu, id, entries[i].data); + if (ret) + break; + } else if (id == LOONGARCH_CSR_ESTAT) { + unsigned long estat, gintc; + + /* ESTAT IP0~IP7 come from GINTC */ + gintc = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_GINTC) & KVM_GINTC_IRQ_MASK; + estat = kvm_read_sw_gcsr(csr, LOONGARCH_CSR_ESTAT) & ~KVM_ESTAT_EXTI_MASK; + entries[i].data = estat | (gintc << VIP_DELTA); + } else { + entries[i].data = kvm_read_sw_gcsr(csr, id); + } + } + + if (!write && copy_to_user(ucsrs->entries, entries, size)) + ret = -EFAULT; + + kfree(entries); + return ret; +} + int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) { int i; @@ -1266,6 +1333,12 @@ long kvm_arch_vcpu_ioctl(struct file *filp, r = kvm_get_reg(vcpu, ®); break; } + case KVM_LOONGARCH_GET_CSR: + r = kvm_loongarch_csr_io(vcpu, argp, false); + break; + case KVM_LOONGARCH_SET_CSR: + r = kvm_loongarch_csr_io(vcpu, argp, true); + break; case KVM_ENABLE_CAP: { struct kvm_enable_cap cap; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 419011097fa8..aade65751721 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1670,4 +1670,8 @@ struct kvm_pre_fault_memory { __u64 padding[5]; }; +/* LoongArch: bulk CSR get/set for migration */ +#define KVM_LOONGARCH_GET_CSR _IOWR(KVMIO, 0xd6, struct kvm_loongarch_csrs) +#define KVM_LOONGARCH_SET_CSR _IOW(KVMIO, 0xd7, struct kvm_loongarch_csrs) + #endif /* __LINUX_KVM_H */ -- 2.43.0