[PATCH v2 0/7] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs

[PATCH v2 0/7] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs

[Sean Christopherson]

Fix a bug where MSHV root partitions (and upper-level VTL code) 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.

This version is based on

  git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git hyperv-next

in order to pickup the VTL changes that are queued for 6.18.  I also
squashed the NEED_RESCHED_LAZY fixes for root and VTL modes into a single
patch, as it should be easy/straightforward to drop the VTL change as needed
if we want this in 6.17 or earlier.

That effectively means the full series is dependent on the VTL changes being
fully merged for 6.18.  But I think that's ok as it's really only the MSHV
changes that have any urgency whatsoever, and I assume that Microsoft is
the only user that truly cares about the MSHV root fix.  I.e. if the whole
thing gets delayed, I think it's only the Hyper-V folks that are impacted.

I have no preference what tree this goes through, or when, and can respin
and/or split as needed.

As with v1, the Hyper-V stuff and non-x86 architectures are compile-tested
only.

v2:
 - Rebase on hyperv-next.
 - Fix and converge the VTL code as well. [Peter, Nuno]

v1: https://lore.kernel.org/all/20250825200622.3759571-1-seanjc@google.com


Sean Christopherson (7):
  Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
  Drivers: hv: Disentangle VTL return cancellation from SIGPENDING
  Drivers: hv: Disable IRQs only after handling pending work before VTL
    return
  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 in root before
    running guest
  Drivers: hv: Use "entry virt" APIs to do work before returning to
    lower VTL

 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                          |  2 ++
 drivers/hv/mshv.h                           |  2 --
 drivers/hv/mshv_common.c                    | 22 ---------------
 drivers/hv/mshv_root_main.c                 | 31 ++++-----------------
 drivers/hv/mshv_vtl_main.c                  | 23 +++++++--------
 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 +-
 22 files changed, 60 insertions(+), 106 deletions(-)
 rename include/linux/{entry-kvm.h => entry-virt.h} (83%)
 rename kernel/entry/{kvm.c => virt.c} (66%)


base-commit: 03ac62a578566730ab3c320f289f7320798ee2e1
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 1/7] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest

[Sean Christopherson]

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.

Note, ideally both the checking and processing of TIF bits would be handled
in common code, to avoid having to keep three separate paths synchronized,
but defer such cleanups to the future to keep the fix as standalone as
possible.

Cc: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Cc: Mukesh R <mrathor@linux.microsoft.com>
Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Fixes: 64503b4f4468 ("Drivers: hv: Introduce mshv_vtl driver")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 drivers/hv/mshv_common.c    | 2 +-
 drivers/hv/mshv_root_main.c | 3 ++-
 drivers/hv/mshv_vtl_main.c  | 3 ++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index 6f227a8a5af7..eb3df3e296bb 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -151,7 +151,7 @@ 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)
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 932932cb91ea..0d849f09160a 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -484,7 +484,8 @@ mshv_vp_wait_for_hv_kick(struct mshv_vp *vp)
 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;
+				 _TIF_NEED_RESCHED  | _TIF_NEED_RESCHED_LAZY |
+				 _TIF_NOTIFY_RESUME;
 	ulong th_flags;
 
 	th_flags = read_thread_flags();
diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index dc6594ae03ad..12f5e77b7095 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -728,7 +728,8 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 	preempt_disable();
 	for (;;) {
 		const unsigned long VTL0_WORK = _TIF_SIGPENDING | _TIF_NEED_RESCHED |
-						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL;
+						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL |
+						_TIF_NEED_RESCHED_LAZY;
 		unsigned long ti_work;
 		u32 cancel;
 		unsigned long irq_flags;
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2 1/7] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest

[Nuno Das Neves]

On 8/27/2025 5:01 PM, Sean Christopherson wrote:
> 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.
> 
> Note, ideally both the checking and processing of TIF bits would be handled
> in common code, to avoid having to keep three separate paths synchronized,
> but defer such cleanups to the future to keep the fix as standalone as
> possible.
> 
> Cc: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> Cc: Mukesh R <mrathor@linux.microsoft.com>
> Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
> Fixes: 64503b4f4468 ("Drivers: hv: Introduce mshv_vtl driver")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  drivers/hv/mshv_common.c    | 2 +-
>  drivers/hv/mshv_root_main.c | 3 ++-
>  drivers/hv/mshv_vtl_main.c  | 3 ++-
>  3 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
> index 6f227a8a5af7..eb3df3e296bb 100644
> --- a/drivers/hv/mshv_common.c
> +++ b/drivers/hv/mshv_common.c
> @@ -151,7 +151,7 @@ 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)
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index 932932cb91ea..0d849f09160a 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -484,7 +484,8 @@ mshv_vp_wait_for_hv_kick(struct mshv_vp *vp)
>  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;
> +				 _TIF_NEED_RESCHED  | _TIF_NEED_RESCHED_LAZY |
> +				 _TIF_NOTIFY_RESUME;
>  	ulong th_flags;
>  
>  	th_flags = read_thread_flags();
> diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
> index dc6594ae03ad..12f5e77b7095 100644
> --- a/drivers/hv/mshv_vtl_main.c
> +++ b/drivers/hv/mshv_vtl_main.c
> @@ -728,7 +728,8 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
>  	preempt_disable();
>  	for (;;) {
>  		const unsigned long VTL0_WORK = _TIF_SIGPENDING | _TIF_NEED_RESCHED |
> -						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL;
> +						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL |
> +						_TIF_NEED_RESCHED_LAZY;
>  		unsigned long ti_work;
>  		u32 cancel;
>  		unsigned long irq_flags;

Tested by compiling with CONFIG_PREEMPT_LAZY=y and booting a guest. For
the test I added a check to confirm _TIF_NEED_RESCHED_LAZY was set and
honored.

Looks good, thanks.

Tested-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 2/7] Drivers: hv: Disentangle VTL return cancellation from SIGPENDING

[Sean Christopherson]

Check for return to a lower VTL being cancelled separately from handling
pending TIF-based work, as there is no need to immediately process pending
work; the kernel will immediately exit to userspace (ignoring preemption)
and handle the pending work at that time.

Disentangling cancellation from the TIF-based work will allow switching to
common virtualization APIs for detecting and processing pending work.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 drivers/hv/mshv_vtl_main.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index 12f5e77b7095..aa09a76f0eff 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -731,19 +731,21 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL |
 						_TIF_NEED_RESCHED_LAZY;
 		unsigned long ti_work;
-		u32 cancel;
 		unsigned long irq_flags;
 		struct hv_vp_assist_page *hvp;
 		int ret;
 
 		local_irq_save(irq_flags);
+		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
+			local_irq_restore(irq_flags);
+			preempt_enable();
+			return -EINTR;
+		}
+
 		ti_work = READ_ONCE(current_thread_info()->flags);
-		cancel = READ_ONCE(mshv_vtl_this_run()->cancel);
-		if (unlikely((ti_work & VTL0_WORK) || cancel)) {
+		if (unlikely(ti_work & VTL0_WORK)) {
 			local_irq_restore(irq_flags);
 			preempt_enable();
-			if (cancel)
-				ti_work |= _TIF_SIGPENDING;
 			ret = mshv_do_pre_guest_mode_work(ti_work);
 			if (ret)
 				return ret;
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2 2/7] Drivers: hv: Disentangle VTL return cancellation from SIGPENDING

[Wei Liu]

On Wed, Aug 27, 2025 at 05:01:51PM -0700, Sean Christopherson wrote:
> Check for return to a lower VTL being cancelled separately from handling
> pending TIF-based work, as there is no need to immediately process pending
> work; the kernel will immediately exit to userspace (ignoring preemption)
> and handle the pending work at that time.
> 
> Disentangling cancellation from the TIF-based work will allow switching to
> common virtualization APIs for detecting and processing pending work.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Thanks for this patch, Sean.

My current plan is to drop this driver from my tree (hence it will
disappear from linux-next soon) because Peter has an objection to the
ABI it introduces. I just have not gotten around to it yet.

I won't apply this patch, the next one and the last one. I have CC'ed
the owner of that driver to this patch here so that your suggestion can
be incorporated in future submissions.

CC Saurabh and Naman.

Thanks,
Wei

> ---
>  drivers/hv/mshv_vtl_main.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
> index 12f5e77b7095..aa09a76f0eff 100644
> --- a/drivers/hv/mshv_vtl_main.c
> +++ b/drivers/hv/mshv_vtl_main.c
> @@ -731,19 +731,21 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
>  						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL |
>  						_TIF_NEED_RESCHED_LAZY;
>  		unsigned long ti_work;
> -		u32 cancel;
>  		unsigned long irq_flags;
>  		struct hv_vp_assist_page *hvp;
>  		int ret;
>  
>  		local_irq_save(irq_flags);
> +		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
> +			local_irq_restore(irq_flags);
> +			preempt_enable();
> +			return -EINTR;
> +		}
> +
>  		ti_work = READ_ONCE(current_thread_info()->flags);
> -		cancel = READ_ONCE(mshv_vtl_this_run()->cancel);
> -		if (unlikely((ti_work & VTL0_WORK) || cancel)) {
> +		if (unlikely(ti_work & VTL0_WORK)) {
>  			local_irq_restore(irq_flags);
>  			preempt_enable();
> -			if (cancel)
> -				ti_work |= _TIF_SIGPENDING;
>  			ret = mshv_do_pre_guest_mode_work(ti_work);
>  			if (ret)
>  				return ret;
> -- 
> 2.51.0.268.g9569e192d0-goog
> 
> 

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 3/7] Drivers: hv: Disable IRQs only after handling pending work before VTL return

[Sean Christopherson]

Swap the order of checking for TIF-based work and cancellation, and disable
IRQs only after checking and processing TIF-based work; checking TIF with
IRQs enabled is a-ok, e.g. IRQs and preemption _must_ be enabled before
handling the pending work.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 drivers/hv/mshv_vtl_main.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index aa09a76f0eff..4ca13c54c0a0 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -735,16 +735,8 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 		struct hv_vp_assist_page *hvp;
 		int ret;
 
-		local_irq_save(irq_flags);
-		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
-			local_irq_restore(irq_flags);
-			preempt_enable();
-			return -EINTR;
-		}
-
 		ti_work = READ_ONCE(current_thread_info()->flags);
 		if (unlikely(ti_work & VTL0_WORK)) {
-			local_irq_restore(irq_flags);
 			preempt_enable();
 			ret = mshv_do_pre_guest_mode_work(ti_work);
 			if (ret)
@@ -753,6 +745,13 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 			continue;
 		}
 
+		local_irq_save(irq_flags);
+		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
+			local_irq_restore(irq_flags);
+			preempt_enable();
+			return -EINTR;
+		}
+
 		mshv_vtl_return(&mshv_vtl_this_run()->cpu_context);
 		local_irq_restore(irq_flags);
 
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 4/7] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper

[Sean Christopherson]

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 d1b8c50941ca..514256b25ba1 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);
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2 4/7] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper

[Thomas Gleixner]

On Wed, Aug 27 2025 at 17:01, Sean Christopherson wrote:
> 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>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 5/7] entry: Rename "kvm" entry code assets to "virt" to genericize APIs

[Sean Christopherson]

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 fe168477caa4..c255048333f0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10200,7 +10200,7 @@ 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 174ee243b349..995489b72535 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
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2 5/7] entry: Rename "kvm" entry code assets to "virt" to genericize APIs

[Thomas Gleixner]

On Wed, Aug 27 2025 at 17:01, Sean Christopherson wrote:
> 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>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 6/7] Drivers: hv: Use common "entry virt" APIs to do work in root before running guest

[Sean Christopherson]

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_root_main.c | 32 ++++++--------------------------
 2 files changed, 7 insertions(+), 26 deletions(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 2e8df09db599..894037afcbf9 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_root_main.c b/drivers/hv/mshv_root_main.c
index 0d849f09160a..7c83f656e071 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>
@@ -481,29 +482,6 @@ 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_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;
-}
-
 /* Must be called with interrupts enabled */
 static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
 {
@@ -524,9 +502,11 @@ 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);
-		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;
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v2 6/7] Drivers: hv: Use common "entry virt" APIs to do work in root before running guest

[Nuno Das Neves]

On 8/27/2025 5:01 PM, Sean Christopherson wrote:
> 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_root_main.c | 32 ++++++--------------------------
>  2 files changed, 7 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 2e8df09db599..894037afcbf9 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_root_main.c b/drivers/hv/mshv_root_main.c
> index 0d849f09160a..7c83f656e071 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>
> @@ -481,29 +482,6 @@ 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_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;
> -}
> -
>  /* Must be called with interrupts enabled */
>  static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
>  {
> @@ -524,9 +502,11 @@ 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);
> -		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;

Also tested mshv_root with 1-6 applied, looks good to me. Possibly Naman,
Saurabh, or Roman can test the mshv_vtl patches, I can't do it
unfortunately.

Tested-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH v2 7/7] Drivers: hv: Use "entry virt" APIs to do work before returning to lower VTL

[Sean Christopherson]

Use the kernel's common "entry virt" APIs to handle pending work prior to
returning to a lower VTL.  Drop the now-defunct common MSHV helper for
doing work as the VTL driver was the last user.

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   | 22 ----------------------
 drivers/hv/mshv_vtl_main.c | 11 +++--------
 4 files changed, 4 insertions(+), 32 deletions(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 894037afcbf9..b00b2b3fe3db 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -85,6 +85,7 @@ config MSHV_VTL
 	# Therefore, do not attempt to access or modify MTRRs here.
 	depends on !MTRR
 	select CPUMASK_OFFSTACK
+	select VIRT_XFER_TO_GUEST_WORK
 	default n
 	help
 	  Select this option to enable Hyper-V VTL driver support.
diff --git a/drivers/hv/mshv.h b/drivers/hv/mshv.h
index 0340a67acd0a..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(ulong th_flags);
-
 #endif /* _MSHV_H */
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index eb3df3e296bb..aa2be51979fd 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -138,25 +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.
- */
-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;
-}
-EXPORT_SYMBOL_GPL(mshv_do_pre_guest_mode_work);
diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index 4ca13c54c0a0..1eabed16aab9 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -8,6 +8,7 @@
  *   Naman Jain <namjain@linux.microsoft.com>
  */
 
+#include <linux/entry-virt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/miscdevice.h>
@@ -727,22 +728,16 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 {
 	preempt_disable();
 	for (;;) {
-		const unsigned long VTL0_WORK = _TIF_SIGPENDING | _TIF_NEED_RESCHED |
-						_TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL |
-						_TIF_NEED_RESCHED_LAZY;
-		unsigned long ti_work;
 		unsigned long irq_flags;
 		struct hv_vp_assist_page *hvp;
 		int ret;
 
-		ti_work = READ_ONCE(current_thread_info()->flags);
-		if (unlikely(ti_work & VTL0_WORK)) {
+		if (__xfer_to_guest_mode_work_pending()) {
 			preempt_enable();
-			ret = mshv_do_pre_guest_mode_work(ti_work);
+			ret = xfer_to_guest_mode_handle_work();
 			if (ret)
 				return ret;
 			preempt_disable();
-			continue;
 		}
 
 		local_irq_save(irq_flags);
-- 
2.51.0.268.g9569e192d0-goog


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv