* [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
@ 2025-08-25 20:06 Sean Christopherson
2025-08-25 20:06 ` [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c Sean Christopherson
` (7 more replies)
0 siblings, 8 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
more generic "virt" APIs (which ideally would have been done when MSHV root
support was added).
Assuming all is well, maybe this could go through the tip tree?
The Hyper-V stuff and non-x86 architectures are compile-tested only.
Sean Christopherson (5):
Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c
Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM
proper
entry: Rename "kvm" entry code assets to "virt" to genericize APIs
Drivers: hv: Use common "entry virt" APIs to do work before running
guest
MAINTAINERS | 2 +-
arch/arm64/kvm/Kconfig | 2 +-
arch/arm64/kvm/arm.c | 3 +-
arch/loongarch/kvm/Kconfig | 2 +-
arch/loongarch/kvm/vcpu.c | 3 +-
arch/riscv/kvm/Kconfig | 2 +-
arch/riscv/kvm/vcpu.c | 3 +-
arch/x86/kvm/Kconfig | 2 +-
arch/x86/kvm/vmx/vmx.c | 1 -
arch/x86/kvm/x86.c | 3 +-
drivers/hv/Kconfig | 1 +
drivers/hv/mshv.h | 2 --
drivers/hv/mshv_common.c | 22 ---------------
drivers/hv/mshv_root_main.c | 31 ++++-----------------
include/linux/{entry-kvm.h => entry-virt.h} | 19 +++++--------
include/linux/kvm_host.h | 17 +++++++++--
include/linux/rcupdate.h | 2 +-
kernel/entry/Makefile | 2 +-
kernel/entry/{kvm.c => virt.c} | 15 ++++------
kernel/rcu/tree.c | 6 ++--
virt/kvm/Kconfig | 2 +-
21 files changed, 49 insertions(+), 93 deletions(-)
rename include/linux/{entry-kvm.h => entry-virt.h} (83%)
rename kernel/entry/{kvm.c => virt.c} (66%)
base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
@ 2025-08-25 20:06 ` Sean Christopherson
2025-08-25 20:06 ` [PATCH 2/5] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest Sean Christopherson
` (6 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Move the root partition's handling of pending thread work fully into
mshv_common.c so that the "work pending" and "do work" code is co-located.
Splitting the flags-to-check logic makes the code unnnecessarily difficult
to maintain, e.g. it would be all too easy to add a check in "do work" but
not in "work pending", and vice versa.
Note, this adds an extra CALL+RET when no work is pending; that will be
remedied in the near feature by switching to common virtualization entry
APIs.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
drivers/hv/mshv.h | 2 +-
drivers/hv/mshv_common.c | 24 +++++++++++++++++++++++-
drivers/hv/mshv_root_main.c | 24 +-----------------------
3 files changed, 25 insertions(+), 25 deletions(-)
diff --git a/drivers/hv/mshv.h b/drivers/hv/mshv.h
index 0340a67acd0a..db3aa3831c43 100644
--- a/drivers/hv/mshv.h
+++ b/drivers/hv/mshv.h
@@ -25,6 +25,6 @@ int hv_call_set_vp_registers(u32 vp_index, u64 partition_id, u16 count,
int hv_call_get_partition_property(u64 partition_id, u64 property_code,
u64 *property_value);
-int mshv_do_pre_guest_mode_work(ulong th_flags);
+int mshv_do_pre_guest_mode_work(void);
#endif /* _MSHV_H */
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index 6f227a8a5af7..1acc47c4be0d 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -146,7 +146,7 @@ EXPORT_SYMBOL_GPL(hv_call_get_partition_property);
*
* Returns: 0 on success, -errno on error.
*/
-int mshv_do_pre_guest_mode_work(ulong th_flags)
+static int __mshv_do_pre_guest_mode_work(ulong th_flags)
{
if (th_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
return -EINTR;
@@ -159,4 +159,26 @@ int mshv_do_pre_guest_mode_work(ulong th_flags)
return 0;
}
+
+int mshv_do_pre_guest_mode_work(void)
+{
+ const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
+ _TIF_NEED_RESCHED | _TIF_NOTIFY_RESUME;
+ ulong th_flags;
+
+ th_flags = read_thread_flags();
+ while (th_flags & work_flags) {
+ int ret;
+
+ /* nb: following will call schedule */
+ ret = __mshv_do_pre_guest_mode_work(th_flags);
+ if (ret)
+ return ret;
+
+ th_flags = read_thread_flags();
+ }
+
+ return 0;
+
+}
EXPORT_SYMBOL_GPL(mshv_do_pre_guest_mode_work);
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 72df774e410a..6f677fb93af0 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -487,28 +487,6 @@ mshv_vp_wait_for_hv_kick(struct mshv_vp *vp)
return 0;
}
-static int mshv_pre_guest_mode_work(struct mshv_vp *vp)
-{
- const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
- _TIF_NEED_RESCHED | _TIF_NOTIFY_RESUME;
- ulong th_flags;
-
- th_flags = read_thread_flags();
- while (th_flags & work_flags) {
- int ret;
-
- /* nb: following will call schedule */
- ret = mshv_do_pre_guest_mode_work(th_flags);
-
- if (ret)
- return ret;
-
- th_flags = read_thread_flags();
- }
-
- return 0;
-}
-
/* Must be called with interrupts enabled */
static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
{
@@ -529,7 +507,7 @@ static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
u32 flags = 0;
struct hv_output_dispatch_vp output;
- ret = mshv_pre_guest_mode_work(vp);
+ ret = mshv_do_pre_guest_mode_work();
if (ret)
break;
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 2/5] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c Sean Christopherson
@ 2025-08-25 20:06 ` Sean Christopherson
2025-08-25 20:06 ` [PATCH 3/5] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper Sean Christopherson
` (5 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Check for NEED_RESCHED_LAZY, not just NEED_RESCHED, prior to transferring
control to a guest. Failure to check for lazy resched can unnecessarily
delay rescheduling until the next tick when using a lazy preemption model.
Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
drivers/hv/mshv_common.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index 1acc47c4be0d..b953b5e21110 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -151,7 +151,7 @@ static int __mshv_do_pre_guest_mode_work(ulong th_flags)
if (th_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
return -EINTR;
- if (th_flags & _TIF_NEED_RESCHED)
+ if (th_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
schedule();
if (th_flags & _TIF_NOTIFY_RESUME)
@@ -163,7 +163,8 @@ static int __mshv_do_pre_guest_mode_work(ulong th_flags)
int mshv_do_pre_guest_mode_work(void)
{
const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
- _TIF_NEED_RESCHED | _TIF_NOTIFY_RESUME;
+ _TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY |
+ _TIF_NOTIFY_RESUME;
ulong th_flags;
th_flags = read_thread_flags();
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 3/5] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c Sean Christopherson
2025-08-25 20:06 ` [PATCH 2/5] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest Sean Christopherson
@ 2025-08-25 20:06 ` Sean Christopherson
2025-08-25 20:06 ` [PATCH 4/5] entry: Rename "kvm" entry code assets to "virt" to genericize APIs Sean Christopherson
` (4 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Move KVM's morphing of pending signals into userspace exits into KVM
proper, and drop the @vcpu param from xfer_to_guest_mode_handle_work().
How KVM responds to -EINTR is a detail that really belongs in KVM itself,
and invoking kvm_handle_signal_exit() from kernel code creates an inverted
module dependency. E.g. attempting to move kvm_handle_signal_exit() into
kvm_main.c would generate an linker error when building kvm.ko as a module.
Dropping KVM details will also converting the KVM "entry" code into a more
generic virtualization framework so that it can be used when running as a
Hyper-V root partition.
Lastly, eliminating usage of "struct kvm_vcpu" outside of KVM is also nice
to have for KVM x86 developers, as keeping the details of kvm_vcpu purely
within KVM allows changing the layout of the structure without having to
boot into a new kernel, e.g. allows rebuilding and reloading kvm.ko with a
modified kvm_vcpu structure as part of debug/development.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/kvm/arm.c | 3 +--
arch/loongarch/kvm/vcpu.c | 3 +--
arch/riscv/kvm/vcpu.c | 3 +--
arch/x86/kvm/vmx/vmx.c | 1 -
arch/x86/kvm/x86.c | 3 +--
include/linux/entry-kvm.h | 11 +++--------
include/linux/kvm_host.h | 13 ++++++++++++-
kernel/entry/kvm.c | 13 +++++--------
8 files changed, 24 insertions(+), 26 deletions(-)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 888f7c7abf54..418fd3043467 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -6,7 +6,6 @@
#include <linux/bug.h>
#include <linux/cpu_pm.h>
-#include <linux/entry-kvm.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kvm_host.h>
@@ -1177,7 +1176,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
/*
* Check conditions before entering the guest
*/
- ret = xfer_to_guest_mode_handle_work(vcpu);
+ ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
if (!ret)
ret = 1;
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index ce478151466c..450545d2fc70 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -4,7 +4,6 @@
*/
#include <linux/kvm_host.h>
-#include <linux/entry-kvm.h>
#include <asm/fpu.h>
#include <asm/lbt.h>
#include <asm/loongarch.h>
@@ -251,7 +250,7 @@ static int kvm_enter_guest_check(struct kvm_vcpu *vcpu)
/*
* Check conditions before entering the guest
*/
- ret = xfer_to_guest_mode_handle_work(vcpu);
+ ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
if (ret < 0)
return ret;
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index f001e56403f9..251e787f2ebc 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -7,7 +7,6 @@
*/
#include <linux/bitops.h>
-#include <linux/entry-kvm.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/kdebug.h>
@@ -910,7 +909,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
run->exit_reason = KVM_EXIT_UNKNOWN;
while (ret > 0) {
/* Check conditions before entering the guest */
- ret = xfer_to_guest_mode_handle_work(vcpu);
+ ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
if (ret)
continue;
ret = 1;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index aa157fe5b7b3..d7c86613e50a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -28,7 +28,6 @@
#include <linux/slab.h>
#include <linux/tboot.h>
#include <linux/trace_events.h>
-#include <linux/entry-kvm.h>
#include <asm/apic.h>
#include <asm/asm.h>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1c49bc681c4..0b13b8bf69e5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -59,7 +59,6 @@
#include <linux/sched/stat.h>
#include <linux/sched/isolation.h>
#include <linux/mem_encrypt.h>
-#include <linux/entry-kvm.h>
#include <linux/suspend.h>
#include <linux/smp.h>
@@ -11241,7 +11240,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
if (__xfer_to_guest_mode_work_pending()) {
kvm_vcpu_srcu_read_unlock(vcpu);
- r = xfer_to_guest_mode_handle_work(vcpu);
+ r = kvm_xfer_to_guest_mode_handle_work(vcpu);
kvm_vcpu_srcu_read_lock(vcpu);
if (r)
return r;
diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 16149f6625e4..3644de7e6019 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -21,8 +21,6 @@
_TIF_NOTIFY_SIGNAL | _TIF_NOTIFY_RESUME | \
ARCH_XFER_TO_GUEST_MODE_WORK)
-struct kvm_vcpu;
-
/**
* arch_xfer_to_guest_mode_handle_work - Architecture specific xfer to guest
* mode work handling function.
@@ -32,12 +30,10 @@ struct kvm_vcpu;
* Invoked from xfer_to_guest_mode_handle_work(). Defaults to NOOP. Can be
* replaced by architecture specific code.
*/
-static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
- unsigned long ti_work);
+static inline int arch_xfer_to_guest_mode_handle_work(unsigned long ti_work);
#ifndef arch_xfer_to_guest_mode_work
-static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
- unsigned long ti_work)
+static inline int arch_xfer_to_guest_mode_handle_work(unsigned long ti_work)
{
return 0;
}
@@ -46,11 +42,10 @@ static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
/**
* xfer_to_guest_mode_handle_work - Check and handle pending work which needs
* to be handled before going to guest mode
- * @vcpu: Pointer to current's VCPU data
*
* Returns: 0 or an error code
*/
-int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu);
+int xfer_to_guest_mode_handle_work(void);
/**
* xfer_to_guest_mode_prepare - Perform last minute preparation work that
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 15656b7fba6c..598b9473e46d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2,7 +2,7 @@
#ifndef __KVM_HOST_H
#define __KVM_HOST_H
-
+#include <linux/entry-kvm.h>
#include <linux/types.h>
#include <linux/hardirq.h>
#include <linux/list.h>
@@ -2450,6 +2450,17 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
vcpu->run->exit_reason = KVM_EXIT_INTR;
vcpu->stat.signal_exits++;
}
+
+static inline int kvm_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
+{
+ int r = xfer_to_guest_mode_handle_work();
+
+ if (r) {
+ WARN_ON_ONCE(r != -EINTR);
+ kvm_handle_signal_exit(vcpu);
+ }
+ return r;
+}
#endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
/*
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 8485f63863af..6fc762eaacca 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -1,17 +1,14 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/entry-kvm.h>
-#include <linux/kvm_host.h>
-static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
+static int xfer_to_guest_mode_work(unsigned long ti_work)
{
do {
int ret;
- if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
- kvm_handle_signal_exit(vcpu);
+ if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
return -EINTR;
- }
if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
schedule();
@@ -19,7 +16,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
if (ti_work & _TIF_NOTIFY_RESUME)
resume_user_mode_work(NULL);
- ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
+ ret = arch_xfer_to_guest_mode_handle_work(ti_work);
if (ret)
return ret;
@@ -28,7 +25,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
return 0;
}
-int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
+int xfer_to_guest_mode_handle_work(void)
{
unsigned long ti_work;
@@ -44,6 +41,6 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
if (!(ti_work & XFER_TO_GUEST_MODE_WORK))
return 0;
- return xfer_to_guest_mode_work(vcpu, ti_work);
+ return xfer_to_guest_mode_work(ti_work);
}
EXPORT_SYMBOL_GPL(xfer_to_guest_mode_handle_work);
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 4/5] entry: Rename "kvm" entry code assets to "virt" to genericize APIs
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
` (2 preceding siblings ...)
2025-08-25 20:06 ` [PATCH 3/5] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper Sean Christopherson
@ 2025-08-25 20:06 ` Sean Christopherson
2025-08-25 20:06 ` [PATCH 5/5] Drivers: hv: Use common "entry virt" APIs to do work before running guest Sean Christopherson
` (3 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Rename the "kvm" entry code files and Kconfigs to use generic "virt"
nomenclature so that the code can be reused by other hypervisors (or
rather, their root/dom0 partition drivers), without incorrectly suggesting
the code somehow relies on and/or involves KVM.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
MAINTAINERS | 2 +-
arch/arm64/kvm/Kconfig | 2 +-
arch/loongarch/kvm/Kconfig | 2 +-
arch/riscv/kvm/Kconfig | 2 +-
arch/x86/kvm/Kconfig | 2 +-
include/linux/{entry-kvm.h => entry-virt.h} | 8 ++++----
include/linux/kvm_host.h | 6 +++---
include/linux/rcupdate.h | 2 +-
kernel/entry/Makefile | 2 +-
kernel/entry/{kvm.c => virt.c} | 2 +-
kernel/rcu/tree.c | 6 +++---
virt/kvm/Kconfig | 2 +-
12 files changed, 19 insertions(+), 19 deletions(-)
rename include/linux/{entry-kvm.h => entry-virt.h} (94%)
rename kernel/entry/{kvm.c => virt.c} (97%)
diff --git a/MAINTAINERS b/MAINTAINERS
index fed6cd812d79..17b9c9d7958e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10211,7 +10211,7 @@ L: linux-kernel@vger.kernel.org
S: Maintained
T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core/entry
F: include/linux/entry-common.h
-F: include/linux/entry-kvm.h
+F: include/linux/entry-virt.h
F: include/linux/irq-entry-common.h
F: kernel/entry/
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 713248f240e0..6f4fc3caa31a 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -25,7 +25,7 @@ menuconfig KVM
select HAVE_KVM_CPU_RELAX_INTERCEPT
select KVM_MMIO
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
- select KVM_XFER_TO_GUEST_WORK
+ select VIRT_XFER_TO_GUEST_WORK
select KVM_VFIO
select HAVE_KVM_DIRTY_RING_ACQ_REL
select NEED_KVM_DIRTY_RING_WITH_BITMAP
diff --git a/arch/loongarch/kvm/Kconfig b/arch/loongarch/kvm/Kconfig
index 40eea6da7c25..ae64bbdf83a7 100644
--- a/arch/loongarch/kvm/Kconfig
+++ b/arch/loongarch/kvm/Kconfig
@@ -31,7 +31,7 @@ config KVM
select KVM_GENERIC_HARDWARE_ENABLING
select KVM_GENERIC_MMU_NOTIFIER
select KVM_MMIO
- select KVM_XFER_TO_GUEST_WORK
+ select VIRT_XFER_TO_GUEST_WORK
select SCHED_INFO
select GUEST_PERF_EVENTS if PERF_EVENTS
help
diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
index 5a62091b0809..c50328212917 100644
--- a/arch/riscv/kvm/Kconfig
+++ b/arch/riscv/kvm/Kconfig
@@ -30,7 +30,7 @@ config KVM
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_GENERIC_HARDWARE_ENABLING
select KVM_MMIO
- select KVM_XFER_TO_GUEST_WORK
+ select VIRT_XFER_TO_GUEST_WORK
select KVM_GENERIC_MMU_NOTIFIER
select SCHED_INFO
select GUEST_PERF_EVENTS if PERF_EVENTS
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 2c86673155c9..f81074b0c0a8 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -40,7 +40,7 @@ config KVM_X86
select HAVE_KVM_MSI
select HAVE_KVM_CPU_RELAX_INTERCEPT
select HAVE_KVM_NO_POLL
- select KVM_XFER_TO_GUEST_WORK
+ select VIRT_XFER_TO_GUEST_WORK
select KVM_GENERIC_DIRTYLOG_READ_PROTECT
select KVM_VFIO
select HAVE_KVM_PM_NOTIFIER if PM
diff --git a/include/linux/entry-kvm.h b/include/linux/entry-virt.h
similarity index 94%
rename from include/linux/entry-kvm.h
rename to include/linux/entry-virt.h
index 3644de7e6019..42c89e3e5ca7 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-virt.h
@@ -1,6 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __LINUX_ENTRYKVM_H
-#define __LINUX_ENTRYKVM_H
+#ifndef __LINUX_ENTRYVIRT_H
+#define __LINUX_ENTRYVIRT_H
#include <linux/static_call_types.h>
#include <linux/resume_user_mode.h>
@@ -10,7 +10,7 @@
#include <linux/tick.h>
/* Transfer to guest mode work */
-#ifdef CONFIG_KVM_XFER_TO_GUEST_WORK
+#ifdef CONFIG_VIRT_XFER_TO_GUEST_WORK
#ifndef ARCH_XFER_TO_GUEST_MODE_WORK
# define ARCH_XFER_TO_GUEST_MODE_WORK (0)
@@ -90,6 +90,6 @@ static inline bool xfer_to_guest_mode_work_pending(void)
lockdep_assert_irqs_disabled();
return __xfer_to_guest_mode_work_pending();
}
-#endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
+#endif /* CONFIG_VIRT_XFER_TO_GUEST_WORK */
#endif
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 598b9473e46d..70ac2267d5d0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2,7 +2,7 @@
#ifndef __KVM_HOST_H
#define __KVM_HOST_H
-#include <linux/entry-kvm.h>
+#include <linux/entry-virt.h>
#include <linux/types.h>
#include <linux/hardirq.h>
#include <linux/list.h>
@@ -2444,7 +2444,7 @@ static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
}
#endif /* CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE */
-#ifdef CONFIG_KVM_XFER_TO_GUEST_WORK
+#ifdef CONFIG_VIRT_XFER_TO_GUEST_WORK
static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
{
vcpu->run->exit_reason = KVM_EXIT_INTR;
@@ -2461,7 +2461,7 @@ static inline int kvm_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
}
return r;
}
-#endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
+#endif /* CONFIG_VIRT_XFER_TO_GUEST_WORK */
/*
* If more than one page is being (un)accounted, @virt must be the address of
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 120536f4c6eb..1e1f3aa375d9 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -129,7 +129,7 @@ static inline void rcu_sysrq_start(void) { }
static inline void rcu_sysrq_end(void) { }
#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
-#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_VIRT_XFER_TO_GUEST_WORK))
void rcu_irq_work_resched(void);
#else
static __always_inline void rcu_irq_work_resched(void) { }
diff --git a/kernel/entry/Makefile b/kernel/entry/Makefile
index 77fcd83dd663..2333d70802e4 100644
--- a/kernel/entry/Makefile
+++ b/kernel/entry/Makefile
@@ -14,4 +14,4 @@ CFLAGS_common.o += -fno-stack-protector
obj-$(CONFIG_GENERIC_IRQ_ENTRY) += common.o
obj-$(CONFIG_GENERIC_SYSCALL) += syscall-common.o syscall_user_dispatch.o
-obj-$(CONFIG_KVM_XFER_TO_GUEST_WORK) += kvm.o
+obj-$(CONFIG_VIRT_XFER_TO_GUEST_WORK) += virt.o
diff --git a/kernel/entry/kvm.c b/kernel/entry/virt.c
similarity index 97%
rename from kernel/entry/kvm.c
rename to kernel/entry/virt.c
index 6fc762eaacca..c52f99249763 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/virt.c
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
-#include <linux/entry-kvm.h>
+#include <linux/entry-virt.h>
static int xfer_to_guest_mode_work(unsigned long ti_work)
{
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8eff357b0436..371447651929 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -573,7 +573,7 @@ void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
}
EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
-#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_VIRT_XFER_TO_GUEST_WORK))
/*
* An empty function that will trigger a reschedule on
* IRQ tail once IRQs get re-enabled on userspace/guest resume.
@@ -602,7 +602,7 @@ noinstr void rcu_irq_work_resched(void)
if (IS_ENABLED(CONFIG_GENERIC_ENTRY) && !(current->flags & PF_VCPU))
return;
- if (IS_ENABLED(CONFIG_KVM_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU))
+ if (IS_ENABLED(CONFIG_VIRT_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU))
return;
instrumentation_begin();
@@ -611,7 +611,7 @@ noinstr void rcu_irq_work_resched(void)
}
instrumentation_end();
}
-#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) */
+#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_VIRT_XFER_TO_GUEST_WORK)) */
#ifdef CONFIG_PROVE_RCU
/**
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 727b542074e7..ce843db53831 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -87,7 +87,7 @@ config HAVE_KVM_VCPU_RUN_PID_CHANGE
config HAVE_KVM_NO_POLL
bool
-config KVM_XFER_TO_GUEST_WORK
+config VIRT_XFER_TO_GUEST_WORK
bool
config HAVE_KVM_PM_NOTIFIER
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 5/5] Drivers: hv: Use common "entry virt" APIs to do work before running guest
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
` (3 preceding siblings ...)
2025-08-25 20:06 ` [PATCH 4/5] entry: Rename "kvm" entry code assets to "virt" to genericize APIs Sean Christopherson
@ 2025-08-25 20:06 ` Sean Christopherson
2025-08-25 21:45 ` [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Wei Liu
` (2 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Sean Christopherson @ 2025-08-25 20:06 UTC (permalink / raw)
To: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
Use the kernel's common "entry virt" APIs to handle pending work prior to
(re)entering guest mode, now that the virt APIs don't have a superfluous
dependency on KVM.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
drivers/hv/Kconfig | 1 +
drivers/hv/mshv.h | 2 --
drivers/hv/mshv_common.c | 45 -------------------------------------
drivers/hv/mshv_root_main.c | 9 +++++---
4 files changed, 7 insertions(+), 50 deletions(-)
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 57623ca7f350..cdb210cd3710 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -66,6 +66,7 @@ config MSHV_ROOT
# no particular order, making it impossible to reassemble larger pages
depends on PAGE_SIZE_4KB
select EVENTFD
+ select VIRT_XFER_TO_GUEST_WORK
default n
help
Select this option to enable support for booting and running as root
diff --git a/drivers/hv/mshv.h b/drivers/hv/mshv.h
index db3aa3831c43..d4813df92b9c 100644
--- a/drivers/hv/mshv.h
+++ b/drivers/hv/mshv.h
@@ -25,6 +25,4 @@ int hv_call_set_vp_registers(u32 vp_index, u64 partition_id, u16 count,
int hv_call_get_partition_property(u64 partition_id, u64 property_code,
u64 *property_value);
-int mshv_do_pre_guest_mode_work(void);
-
#endif /* _MSHV_H */
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index b953b5e21110..aa2be51979fd 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -138,48 +138,3 @@ int hv_call_get_partition_property(u64 partition_id,
return 0;
}
EXPORT_SYMBOL_GPL(hv_call_get_partition_property);
-
-/*
- * Handle any pre-processing before going into the guest mode on this cpu, most
- * notably call schedule(). Must be invoked with both preemption and
- * interrupts enabled.
- *
- * Returns: 0 on success, -errno on error.
- */
-static int __mshv_do_pre_guest_mode_work(ulong th_flags)
-{
- if (th_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
- return -EINTR;
-
- if (th_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
- schedule();
-
- if (th_flags & _TIF_NOTIFY_RESUME)
- resume_user_mode_work(NULL);
-
- return 0;
-}
-
-int mshv_do_pre_guest_mode_work(void)
-{
- const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
- _TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY |
- _TIF_NOTIFY_RESUME;
- ulong th_flags;
-
- th_flags = read_thread_flags();
- while (th_flags & work_flags) {
- int ret;
-
- /* nb: following will call schedule */
- ret = __mshv_do_pre_guest_mode_work(th_flags);
- if (ret)
- return ret;
-
- th_flags = read_thread_flags();
- }
-
- return 0;
-
-}
-EXPORT_SYMBOL_GPL(mshv_do_pre_guest_mode_work);
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 6f677fb93af0..387491ca16d6 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -8,6 +8,7 @@
* Authors: Microsoft Linux virtualization team
*/
+#include <linux/entry-virt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
@@ -507,9 +508,11 @@ static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
u32 flags = 0;
struct hv_output_dispatch_vp output;
- ret = mshv_do_pre_guest_mode_work();
- if (ret)
- break;
+ if (__xfer_to_guest_mode_work_pending()) {
+ ret = xfer_to_guest_mode_handle_work();
+ if (ret)
+ break;
+ }
if (vp->run.flags.intercept_suspend)
flags |= HV_DISPATCH_VP_FLAG_CLEAR_INTERCEPT_SUSPEND;
--
2.51.0.261.g7ce5a0a67e-goog
^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
` (4 preceding siblings ...)
2025-08-25 20:06 ` [PATCH 5/5] Drivers: hv: Use common "entry virt" APIs to do work before running guest Sean Christopherson
@ 2025-08-25 21:45 ` Wei Liu
2025-08-25 22:23 ` Peter Zijlstra
2025-08-25 23:08 ` Nuno Das Neves
7 siblings, 0 replies; 12+ messages in thread
From: Wei Liu @ 2025-08-25 21:45 UTC (permalink / raw)
To: Sean Christopherson
Cc: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Paolo Bonzini, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, Dave Hansen, x86, K. Y. Srinivasan,
Haiyang Zhang, Wei Liu, Dexuan Cui, Peter Zijlstra,
Andy Lutomirski, Paul E. McKenney, Frederic Weisbecker,
Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Boqun Feng,
Uladzislau Rezki, linux-kernel, linux-arm-kernel, kvmarm, kvm,
loongarch, kvm-riscv, linux-riscv, linux-hyperv, rcu, mrathor,
nunodasneves
On Mon, Aug 25, 2025 at 01:06:17PM -0700, Sean Christopherson wrote:
> Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> more generic "virt" APIs (which ideally would have been done when MSHV root
> support was added).
>
It is nice to have a common infrastructure.
Cc Mukesh and Nuno for review and test.
Thanks,
Wei
> Assuming all is well, maybe this could go through the tip tree?
>
> The Hyper-V stuff and non-x86 architectures are compile-tested only.
>
> Sean Christopherson (5):
> Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c
> Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
> entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM
> proper
> entry: Rename "kvm" entry code assets to "virt" to genericize APIs
> Drivers: hv: Use common "entry virt" APIs to do work before running
> guest
>
> MAINTAINERS | 2 +-
> arch/arm64/kvm/Kconfig | 2 +-
> arch/arm64/kvm/arm.c | 3 +-
> arch/loongarch/kvm/Kconfig | 2 +-
> arch/loongarch/kvm/vcpu.c | 3 +-
> arch/riscv/kvm/Kconfig | 2 +-
> arch/riscv/kvm/vcpu.c | 3 +-
> arch/x86/kvm/Kconfig | 2 +-
> arch/x86/kvm/vmx/vmx.c | 1 -
> arch/x86/kvm/x86.c | 3 +-
> drivers/hv/Kconfig | 1 +
> drivers/hv/mshv.h | 2 --
> drivers/hv/mshv_common.c | 22 ---------------
> drivers/hv/mshv_root_main.c | 31 ++++-----------------
> include/linux/{entry-kvm.h => entry-virt.h} | 19 +++++--------
> include/linux/kvm_host.h | 17 +++++++++--
> include/linux/rcupdate.h | 2 +-
> kernel/entry/Makefile | 2 +-
> kernel/entry/{kvm.c => virt.c} | 15 ++++------
> kernel/rcu/tree.c | 6 ++--
> virt/kvm/Kconfig | 2 +-
> 21 files changed, 49 insertions(+), 93 deletions(-)
> rename include/linux/{entry-kvm.h => entry-virt.h} (83%)
> rename kernel/entry/{kvm.c => virt.c} (66%)
>
>
> base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
> --
> 2.51.0.261.g7ce5a0a67e-goog
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
` (5 preceding siblings ...)
2025-08-25 21:45 ` [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Wei Liu
@ 2025-08-25 22:23 ` Peter Zijlstra
2025-08-25 22:26 ` Wei Liu
2025-08-25 23:08 ` Nuno Das Neves
7 siblings, 1 reply; 12+ messages in thread
From: Peter Zijlstra @ 2025-08-25 22:23 UTC (permalink / raw)
To: Sean Christopherson
Cc: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Paolo Bonzini, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, Dave Hansen, x86, K. Y. Srinivasan,
Haiyang Zhang, Wei Liu, Dexuan Cui, Andy Lutomirski,
Paul E. McKenney, Frederic Weisbecker, Neeraj Upadhyay,
Joel Fernandes, Josh Triplett, Boqun Feng, Uladzislau Rezki,
linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
On Mon, Aug 25, 2025 at 01:06:17PM -0700, Sean Christopherson wrote:
> Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> more generic "virt" APIs (which ideally would have been done when MSHV root
> support was added).
>
> Assuming all is well, maybe this could go through the tip tree?
>
> The Hyper-V stuff and non-x86 architectures are compile-tested only.
I suspect there's more of this wreckage in the new VTL driver that
they just put in:
https://lore.kernel.org/all/20250729051436.190703-3-namjain@linux.microsoft.com/
although ideally they rip that thing out. I don't know how that code can
ever be correct.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-25 22:23 ` Peter Zijlstra
@ 2025-08-25 22:26 ` Wei Liu
0 siblings, 0 replies; 12+ messages in thread
From: Wei Liu @ 2025-08-25 22:26 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Sean Christopherson, Marc Zyngier, Oliver Upton, Catalin Marinas,
Will Deacon, Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel,
Paul Walmsley, Palmer Dabbelt, Albert Ou, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Andy Lutomirski, Paul E. McKenney, Frederic Weisbecker,
Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Boqun Feng,
Uladzislau Rezki, linux-kernel, linux-arm-kernel, kvmarm, kvm,
loongarch, kvm-riscv, linux-riscv, linux-hyperv, rcu
On Tue, Aug 26, 2025 at 12:23:19AM +0200, Peter Zijlstra wrote:
> On Mon, Aug 25, 2025 at 01:06:17PM -0700, Sean Christopherson wrote:
> > Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> > deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> > more generic "virt" APIs (which ideally would have been done when MSHV root
> > support was added).
> >
> > Assuming all is well, maybe this could go through the tip tree?
> >
> > The Hyper-V stuff and non-x86 architectures are compile-tested only.
>
> I suspect there's more of this wreckage in the new VTL driver that
> they just put in:
>
> https://lore.kernel.org/all/20250729051436.190703-3-namjain@linux.microsoft.com/
>
> although ideally they rip that thing out. I don't know how that code can
> ever be correct.
Please give us some time, Peter. I have asked the corresponding team to
respond to your comments.
Wei
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
` (6 preceding siblings ...)
2025-08-25 22:23 ` Peter Zijlstra
@ 2025-08-25 23:08 ` Nuno Das Neves
2025-08-26 0:27 ` Sean Christopherson
7 siblings, 1 reply; 12+ messages in thread
From: Nuno Das Neves @ 2025-08-25 23:08 UTC (permalink / raw)
To: Sean Christopherson, Marc Zyngier, Oliver Upton, Catalin Marinas,
Will Deacon, Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel,
Paul Walmsley, Palmer Dabbelt, Albert Ou, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: linux-kernel, linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv,
linux-riscv, linux-hyperv, rcu
On 8/25/2025 1:06 PM, Sean Christopherson wrote:
> Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> more generic "virt" APIs (which ideally would have been done when MSHV root
> support was added).
>
> Assuming all is well, maybe this could go through the tip tree?
>
> The Hyper-V stuff and non-x86 architectures are compile-tested only.
>
Thanks Sean, I can test the root partition changes.
A similar change will be needed in mshv_vtl_main.c since it also calls
mshv_do_pre_guest_mode_work() (hence the "common" in mshv_common.c).
Also, is it possible to make all the mshv driver changes in a single patch?
It seems like it would be cleaner than refactoring it in patches 1 & 2 and
then deleting all the refactored code in patch 5.
Thanks
Nuno
> Sean Christopherson (5):
> Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c
> Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
> entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM
> proper
> entry: Rename "kvm" entry code assets to "virt" to genericize APIs
> Drivers: hv: Use common "entry virt" APIs to do work before running
> guest
>
> MAINTAINERS | 2 +-
> arch/arm64/kvm/Kconfig | 2 +-
> arch/arm64/kvm/arm.c | 3 +-
> arch/loongarch/kvm/Kconfig | 2 +-
> arch/loongarch/kvm/vcpu.c | 3 +-
> arch/riscv/kvm/Kconfig | 2 +-
> arch/riscv/kvm/vcpu.c | 3 +-
> arch/x86/kvm/Kconfig | 2 +-
> arch/x86/kvm/vmx/vmx.c | 1 -
> arch/x86/kvm/x86.c | 3 +-
> drivers/hv/Kconfig | 1 +
> drivers/hv/mshv.h | 2 --
> drivers/hv/mshv_common.c | 22 ---------------
> drivers/hv/mshv_root_main.c | 31 ++++-----------------
> include/linux/{entry-kvm.h => entry-virt.h} | 19 +++++--------
> include/linux/kvm_host.h | 17 +++++++++--
> include/linux/rcupdate.h | 2 +-
> kernel/entry/Makefile | 2 +-
> kernel/entry/{kvm.c => virt.c} | 15 ++++------
> kernel/rcu/tree.c | 6 ++--
> virt/kvm/Kconfig | 2 +-
> 21 files changed, 49 insertions(+), 93 deletions(-)
> rename include/linux/{entry-kvm.h => entry-virt.h} (83%)
> rename kernel/entry/{kvm.c => virt.c} (66%)
>
>
> base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-25 23:08 ` Nuno Das Neves
@ 2025-08-26 0:27 ` Sean Christopherson
2025-08-26 16:58 ` Wei Liu
0 siblings, 1 reply; 12+ messages in thread
From: Sean Christopherson @ 2025-08-26 0:27 UTC (permalink / raw)
To: Nuno Das Neves
Cc: Marc Zyngier, Oliver Upton, Catalin Marinas, Will Deacon,
Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel, Paul Walmsley,
Palmer Dabbelt, Albert Ou, Paolo Bonzini, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, Dave Hansen, x86, K. Y. Srinivasan,
Haiyang Zhang, Wei Liu, Dexuan Cui, Peter Zijlstra,
Andy Lutomirski, Paul E. McKenney, Frederic Weisbecker,
Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Boqun Feng,
Uladzislau Rezki, linux-kernel, linux-arm-kernel, kvmarm, kvm,
loongarch, kvm-riscv, linux-riscv, linux-hyperv, rcu
On Mon, Aug 25, 2025, Nuno Das Neves wrote:
> On 8/25/2025 1:06 PM, Sean Christopherson wrote:
> > Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> > deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> > more generic "virt" APIs (which ideally would have been done when MSHV root
> > support was added).
> >
> > Assuming all is well, maybe this could go through the tip tree?
> >
> > The Hyper-V stuff and non-x86 architectures are compile-tested only.
> >
>
> Thanks Sean, I can test the root partition changes.
>
> A similar change will be needed in mshv_vtl_main.c since it also calls
> mshv_do_pre_guest_mode_work() (hence the "common" in mshv_common.c).
Oof, more dependencies. I suppose the easiest thing would be to send a series
against
git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git queue
and then route everything through there?
Alternatively, frontload the MSHV fixes (which I'll do regardless) and take those
through hyperv and the rest through the tip tree? That seems like an absurd
amount of juggling though, especially if we want to get the cleanups into 6.18.
And if none of these lands, it's MSHV that'll suffer the most, so betting it all
on the hyperv tree doesn't seem terrible.
> Also, is it possible to make all the mshv driver changes in a single patch?
It's certainly possible, but I'd prefer not do to that.
> It seems like it would be cleaner than refactoring it in patches 1 & 2 and
> then deleting all the refactored code in patch 5.
Only if you don't care about backporting fixes, bisection, or maintaining code.
E.g. if checking NEED_RESCHED_LAZY somehow causes issues, it would be really nice
for that to bisect to exactly that patch, not a patch that also switches to a
completely different set of APIs.
And if someone is wants the fixes in a pre-6.18 kernel, they don't need to
backport all of the KVM and entry code changes just to get the fix.
As for the maintenance headache, see above.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs
2025-08-26 0:27 ` Sean Christopherson
@ 2025-08-26 16:58 ` Wei Liu
0 siblings, 0 replies; 12+ messages in thread
From: Wei Liu @ 2025-08-26 16:58 UTC (permalink / raw)
To: Sean Christopherson
Cc: Nuno Das Neves, Marc Zyngier, Oliver Upton, Catalin Marinas,
Will Deacon, Tianrui Zhao, Bibo Mao, Huacai Chen, Anup Patel,
Paul Walmsley, Palmer Dabbelt, Albert Ou, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
K. Y. Srinivasan, Haiyang Zhang, Wei Liu, Dexuan Cui,
Peter Zijlstra, Andy Lutomirski, Paul E. McKenney,
Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki, linux-kernel,
linux-arm-kernel, kvmarm, kvm, loongarch, kvm-riscv, linux-riscv,
linux-hyperv, rcu
On Mon, Aug 25, 2025 at 05:27:16PM -0700, Sean Christopherson wrote:
> On Mon, Aug 25, 2025, Nuno Das Neves wrote:
> > On 8/25/2025 1:06 PM, Sean Christopherson wrote:
> > > Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> > > deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> > > more generic "virt" APIs (which ideally would have been done when MSHV root
> > > support was added).
> > >
> > > Assuming all is well, maybe this could go through the tip tree?
> > >
> > > The Hyper-V stuff and non-x86 architectures are compile-tested only.
> > >
> >
> > Thanks Sean, I can test the root partition changes.
> >
> > A similar change will be needed in mshv_vtl_main.c since it also calls
> > mshv_do_pre_guest_mode_work() (hence the "common" in mshv_common.c).
>
> Oof, more dependencies. I suppose the easiest thing would be to send a series
> against
>
> git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git queue
>
> and then route everything through there?
Our fixes branch is on 6.17-rc1. You can use it as a base if you want
to.
>
> Alternatively, frontload the MSHV fixes (which I'll do regardless) and take those
> through hyperv and the rest through the tip tree? That seems like an absurd
> amount of juggling though, especially if we want to get the cleanups into 6.18.
> And if none of these lands, it's MSHV that'll suffer the most, so betting it all
> on the hyperv tree doesn't seem terrible.
>
I'm happy to do it however the community sees fit.
> > Also, is it possible to make all the mshv driver changes in a single patch?
>
> It's certainly possible, but I'd prefer not do to that.
>
> > It seems like it would be cleaner than refactoring it in patches 1 & 2 and
> > then deleting all the refactored code in patch 5.
>
> Only if you don't care about backporting fixes, bisection, or maintaining code.
>
> E.g. if checking NEED_RESCHED_LAZY somehow causes issues, it would be really nice
> for that to bisect to exactly that patch, not a patch that also switches to a
> completely different set of APIs.
>
> And if someone is wants the fixes in a pre-6.18 kernel, they don't need to
> backport all of the KVM and entry code changes just to get the fix.
+1 on this.
Thanks,
Wei
>
> As for the maintenance headache, see above.
^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2025-08-26 16:58 UTC | newest]
Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
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2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c Sean Christopherson
2025-08-25 20:06 ` [PATCH 2/5] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest Sean Christopherson
2025-08-25 20:06 ` [PATCH 3/5] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper Sean Christopherson
2025-08-25 20:06 ` [PATCH 4/5] entry: Rename "kvm" entry code assets to "virt" to genericize APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 5/5] Drivers: hv: Use common "entry virt" APIs to do work before running guest Sean Christopherson
2025-08-25 21:45 ` [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Wei Liu
2025-08-25 22:23 ` Peter Zijlstra
2025-08-25 22:26 ` Wei Liu
2025-08-25 23:08 ` Nuno Das Neves
2025-08-26 0:27 ` Sean Christopherson
2025-08-26 16:58 ` Wei Liu
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