linux-kernel - RE: [PATCH v3 1/3] Drivers: hv: Use nested hypercall for post message and signal event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <SN6PR02MB41578D12A564ECC32BEFD6F1D44BA@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Fri, 11 Jul 2025 19:25:30 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "bhelgaas@...gle.com"
	<bhelgaas@...gle.com>, "romank@...ux.microsoft.com"
	<romank@...ux.microsoft.com>
CC: "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
	<haiyangz@...rosoft.com>, "decui@...rosoft.com" <decui@...rosoft.com>,
	"catalin.marinas@....com" <catalin.marinas@....com>, "will@...nel.org"
	<will@...nel.org>, "mingo@...hat.com" <mingo@...hat.com>, "bp@...en8.de"
	<bp@...en8.de>, "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"hpa@...or.com" <hpa@...or.com>, "lpieralisi@...nel.org"
	<lpieralisi@...nel.org>, "kw@...ux.com" <kw@...ux.com>, "robh@...nel.org"
	<robh@...nel.org>, "jinankjain@...ux.microsoft.com"
	<jinankjain@...ux.microsoft.com>, "skinsburskii@...ux.microsoft.com"
	<skinsburskii@...ux.microsoft.com>, "mrathor@...ux.microsoft.com"
	<mrathor@...ux.microsoft.com>, "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH v3 1/3] Drivers: hv: Use nested hypercall for post message
 and signal event

From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, July 11, 2025 12:19 PM
> 
> When running nested, these hypercalls must be sent to the L0 hypervisor
> or VMBus will fail.
> 
> Remove hv_do_nested_hypercall() and hv_do_fast_nested_hypercall8()
> altogether and open-code these cases, since there are only 2 and all
> they do is add the nested bit.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> Reviewed-by: Roman Kisel <romank@...ux.microsoft.com>
> ---
>  arch/x86/include/asm/mshyperv.h | 20 --------------------
>  drivers/hv/connection.c         |  5 ++++-
>  drivers/hv/hv.c                 |  6 ++++--
>  3 files changed, 8 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index e1752ba47e67..ab097a3a8b75 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -112,12 +112,6 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
>  	return hv_status;
>  }
> 
> -/* Hypercall to the L0 hypervisor */
> -static inline u64 hv_do_nested_hypercall(u64 control, void *input, void *output)
> -{
> -	return hv_do_hypercall(control | HV_HYPERCALL_NESTED, input, output);
> -}
> -
>  /* Fast hypercall with 8 bytes of input and no output */
>  static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
>  {
> @@ -165,13 +159,6 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
>  	return _hv_do_fast_hypercall8(control, input1);
>  }
> 
> -static inline u64 hv_do_fast_nested_hypercall8(u16 code, u64 input1)
> -{
> -	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
> -
> -	return _hv_do_fast_hypercall8(control, input1);
> -}
> -
>  /* Fast hypercall with 16 bytes of input */
>  static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
>  {
> @@ -223,13 +210,6 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
>  	return _hv_do_fast_hypercall16(control, input1, input2);
>  }
> 
> -static inline u64 hv_do_fast_nested_hypercall16(u16 code, u64 input1, u64 input2)
> -{
> -	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
> -
> -	return _hv_do_fast_hypercall16(control, input1, input2);
> -}
> -
>  extern struct hv_vp_assist_page **hv_vp_assist_page;
> 
>  static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index be490c598785..1fe3573ae52a 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -519,7 +519,10 @@ void vmbus_set_event(struct vmbus_channel *channel)
>  		else
>  			WARN_ON_ONCE(1);
>  	} else {
> -		hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
> +		u64 control = HVCALL_SIGNAL_EVENT;
> +
> +		control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
> +		hv_do_fast_hypercall8(control, channel->sig_event);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(vmbus_set_event);
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 308c8f279df8..b14c5f9e0ef2 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -85,8 +85,10 @@ int hv_post_message(union hv_connection_id connection_id,
>  		else
>  			status = HV_STATUS_INVALID_PARAMETER;
>  	} else {
> -		status = hv_do_hypercall(HVCALL_POST_MESSAGE,
> -					 aligned_msg, NULL);
> +		u64 control = HVCALL_POST_MESSAGE;
> +
> +		control |= hv_nested ? HV_HYPERCALL_NESTED : 0;
> +		status = hv_do_hypercall(control, aligned_msg, NULL);
>  	}
> 
>  	local_irq_restore(flags);
> --
> 2.34.1

Reviewed-by: Michael Kelley <mhklinux@...look.com>