linux-kernel - Re: [PATCH 1/7] x86/hyperv: Fix output argument to hypercall that changes page visibility

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Message-ID: <Z84wsC8ADzZusVVY@liuwe-devbox-ubuntu-v2.lamzopl0uupeniq2etz1fddiyg.xx.internal.cloudapp.net>
Date: Mon, 10 Mar 2025 00:22:08 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: mhklinux@...look.com, kys@...rosoft.com, haiyangz@...rosoft.com,
	wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	hpa@...or.com, lpieralisi@...nel.org, kw@...ux.com,
	manivannan.sadhasivam@...aro.org, robh@...nel.org,
	bhelgaas@...gle.com, arnd@...db.de, x86@...nel.org,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/7] x86/hyperv: Fix output argument to hypercall that
 changes page visibility

On Wed, Feb 26, 2025 at 02:59:53PM -0800, Nuno Das Neves wrote:
> On 2/26/2025 12:06 PM, mhkelley58@...il.com wrote:
> > From: Michael Kelley <mhklinux@...look.com>
> > 
> > The hypercall in hv_mark_gpa_visibility() is invoked with an input
> > argument and an output argument. The output argument ostensibly returns
> > the number of pages that were processed. But in fact, the hypercall does
> > not provide any output, so the output argument is spurious.
> > 
> > The spurious argument is harmless because Hyper-V ignores it, but in the
> > interest of correctness and to avoid the potential for future problems,
> > remove it.
> > 
> > Signed-off-by: Michael Kelley <mhklinux@...look.com>
> > ---
> > I have not provided a "Fixes:" tag because the error causes no impact.
> > There's no value in backporting the fix.
> > 
> >  arch/x86/hyperv/ivm.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> > index dd68d9ad9b22..ec7880271cf9 100644
> > --- a/arch/x86/hyperv/ivm.c
> > +++ b/arch/x86/hyperv/ivm.c
> > @@ -464,7 +464,6 @@ static int hv_mark_gpa_visibility(u16 count, const u64 pfn[],
> >  			   enum hv_mem_host_visibility visibility)
> >  {
> >  	struct hv_gpa_range_for_visibility *input;
> > -	u16 pages_processed;
> >  	u64 hv_status;
> >  	unsigned long flags;
> >  
> > @@ -493,7 +492,7 @@ static int hv_mark_gpa_visibility(u16 count, const u64 pfn[],
> >  	memcpy((void *)input->gpa_page_list, pfn, count * sizeof(*pfn));
> >  	hv_status = hv_do_rep_hypercall(
> >  			HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY, count,
> > -			0, input, &pages_processed);
> > +			0, input, NULL);
> >  	local_irq_restore(flags);
> >  
> >  	if (hv_result_success(hv_status))
> 
> Reviewed-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>

Applied to hyperv-fixes, thanks!