linux-kernel - RE: [PATCH 1/2] x86/hyperv: Move hv_do_rep

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Message-ID: <CY4PR21MB15863413859BBF15CADD214CD74A9@CY4PR21MB1586.namprd21.prod.outlook.com>
Date:   Sun, 18 Apr 2021 14:42:55 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Wei Liu <wei.liu@...nel.org>,
        Joseph Salisbury <Joseph.Salisbury@...rosoft.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] x86/hyperv: Move hv_do_rep_hypercall to asm-generic

From: Wei Liu <wei.liu@...nel.org> Sent: Sunday, April 18, 2021 6:09 AM
> On Fri, Apr 16, 2021 at 05:43:02PM -0700, Joseph Salisbury wrote:
> > From: Joseph Salisbury <joseph.salisbury@...rosoft.com>
> >
> > This patch makes no functional changes.  It simply moves hv_do_rep_hypercall()
> > out of arch/x86/include/asm/mshyperv.h and into asm-generic/mshyperv.h
> >
> > hv_do_rep_hypercall() is architecture independent, so it makes sense that it
> > should be in the architecture independent mshyperv.h, not in the x86-specific
> > mshyperv.h.
> >
> > This is done in preperation for a follow up patch which creates a consistent
> > pattern for checking Hyper-V hypercall status.
> >
> > Signed-off-by: Joseph Salisbury <joseph.salisbury@...rosoft.com>
> > ---
> [...]
> > +static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size,
> > +				      void *input, void *output)
> > +{
> > +	u64 control = code;
> > +	u64 status;
> > +	u16 rep_comp;
> > +
> > +	control |= (u64)varhead_size << HV_HYPERCALL_VARHEAD_OFFSET;
> > +	control |= (u64)rep_count << HV_HYPERCALL_REP_COMP_OFFSET;
> > +
> > +	do {
> > +		status = hv_do_hypercall(control, input, output);
> > +		if ((status & HV_HYPERCALL_RESULT_MASK) != HV_STATUS_SUCCESS)
> > +			return status;
> > +
> > +		/* Bits 32-43 of status have 'Reps completed' data. */
> > +		rep_comp = (status & HV_HYPERCALL_REP_COMP_MASK) >>
> > +			HV_HYPERCALL_REP_COMP_OFFSET;
> > +
> > +		control &= ~HV_HYPERCALL_REP_START_MASK;
> > +		control |= (u64)rep_comp << HV_HYPERCALL_REP_START_OFFSET;
> > +
> > +		touch_nmi_watchdog();
> 
> This seems to be missing in Arm. Does it compile?
> 
> Wei.

touch_nmi_watchdog() is defined as "static inline" in include/linux/nmi.h.  So
it should be present in all architectures.  It calls arch_touch_nmi_watchdog,
which is an empty function if CONFIG_HAVE_NMI_WATCHDOG is not defined,
as is the case on ARM64.

Michael

> 
> > +	} while (rep_comp < rep_count);
> > +
> > +	return status;
> > +}
> >
> >  /* Generate the guest OS identifier as described in the Hyper-V TLFS */
> >  static inline  __u64 generate_guest_id(__u64 d_info1, __u64 kernel_version,
> > --
> > 2.17.1
> >