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[1/1] fbdev/hyperv_fb: Fix logic error for Gen2 VMs in hvfb_getmem()

Message ID 20240201060022.233666-1-mhklinux@outlook.com
State New
Headers show
Series [1/1] fbdev/hyperv_fb: Fix logic error for Gen2 VMs in hvfb_getmem() | expand

Commit Message

mhkelley58@gmail.com Feb. 1, 2024, 6 a.m. UTC 
From: Michael Kelley <mhklinux@outlook.com>

A recent commit removing the use of screen_info introduced a logic
error. The error causes hvfb_getmem() to always return -ENOMEM
for Generation 2 VMs. As a result, the Hyper-V frame buffer
device fails to initialize. The error was introduced by removing
an "else if" clause, leaving Gen2 VMs to always take the -ENOMEM
error path.

Fix the problem by removing the error path "else" clause. Gen 2
VMs now always proceed through the MMIO memory allocation code,
but with "base" and "size" defaulting to 0.

Fixes: 0aa0838c84da ("fbdev/hyperv_fb: Remove firmware framebuffers with aperture helpers")
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
 drivers/video/fbdev/hyperv_fb.c | 2 --
 1 file changed, 2 deletions(-)

Comments

Michael Kelley Feb. 9, 2024, 3:23 p.m. UTC | #1 
From: Thomas Zimmermann <tzimmermann@suse.de> Sent: Thursday, February 1, 2024 12:17 AM
> 
> Hi
> 
> Am 01.02.24 um 07:00 schrieb mhkelley58@gmail.com:
> > From: Michael Kelley <mhklinux@outlook.com>
> >
> > A recent commit removing the use of screen_info introduced a logic
> > error. The error causes hvfb_getmem() to always return -ENOMEM
> > for Generation 2 VMs. As a result, the Hyper-V frame buffer
> > device fails to initialize. The error was introduced by removing
> > an "else if" clause, leaving Gen2 VMs to always take the -ENOMEM
> > error path.
> >
> > Fix the problem by removing the error path "else" clause. Gen 2
> > VMs now always proceed through the MMIO memory allocation code,
> > but with "base" and "size" defaulting to 0.
> 
> Indeed, that's how it was supposed to work. IDK how I didn't notice this
> bug. Thanks a lot for the fix.
> 
> >
> > Fixes: 0aa0838c84da ("fbdev/hyperv_fb: Remove firmware framebufferswith aperture helpers")
> > Signed-off-by: Michael Kelley <mhklinux@outlook.com>
> 
> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

Wei Liu and Helge Deller --

Should this fix go through the Hyper-V tree or the fbdev tree?   I'm not
aware of a reason that it really matters, but it needs to be one or the
other, and sooner rather than later, because the Hyper-V driver is broken
starting in 6.8-rc1.

Michael

> 
> > ---
> >   drivers/video/fbdev/hyperv_fb.c | 2 --
> >   1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/video/fbdev/hyperv_fb.c
> b/drivers/video/fbdev/hyperv_fb.c
> > index c26ee6fd73c9..8fdccf033b2d 100644
> > --- a/drivers/video/fbdev/hyperv_fb.c
> > +++ b/drivers/video/fbdev/hyperv_fb.c
> > @@ -1010,8 +1010,6 @@ static int hvfb_getmem(struct hv_device *hdev,
> struct fb_info *info)
> >   			goto getmem_done;
> >   		}
> >   		pr_info("Unable to allocate enough contiguous physical memory on Gen 1 VM. Using MMIO instead.\n");
> > -	} else {
> > -		goto err1;
> >   	}
> >
> >   	/*
>
Wei Liu March 1, 2024, 9:25 a.m. UTC | #2 
On Fri, Feb 09, 2024 at 04:53:37PM +0100, Helge Deller wrote:
> On 2/9/24 16:23, Michael Kelley wrote:
> > From: Thomas Zimmermann <tzimmermann@suse.de> Sent: Thursday, February 1, 2024 12:17 AM
[...]
> > 
> > Wei Liu and Helge Deller --
> > 
> > Should this fix go through the Hyper-V tree or the fbdev tree?   I'm not
> > aware of a reason that it really matters, but it needs to be one or the
> > other, and sooner rather than later, because the Hyper-V driver is broken
> > starting in 6.8-rc1.
> 
> I'm fine with either.
> If there is an upcoming hyper-v pull request, I'm fine if this is included
> there. If not, let me know and I can take it via fbdev.

I've applied this to the hyperv-fixes tree. Thanks.
Michael Kelley March 1, 2024, 4:41 p.m. UTC | #3 
From: Wei Liu <wei.liu@kernel.org> Sent: Friday, March 1, 2024 1:26 AM
> 
> On Fri, Feb 09, 2024 at 04:53:37PM +0100, Helge Deller wrote:
> > On 2/9/24 16:23, Michael Kelley wrote:
> > > From: Thomas Zimmermann <tzimmermann@suse.de> Sent: Thursday, February 1, 2024 12:17 AM
> [...]
> > >
> > > Wei Liu and Helge Deller --
> > >
> > > Should this fix go through the Hyper-V tree or the fbdev tree?   I'm not
> > > aware of a reason that it really matters, but it needs to be one or the
> > > other, and sooner rather than later, because the Hyper-V driver is broken
> > > starting in 6.8-rc1.
> >
> > I'm fine with either.
> > If there is an upcoming hyper-v pull request, I'm fine if this is included
> > there. If not, let me know and I can take it via fbdev.
> 
> I've applied this to the hyperv-fixes tree. Thanks.

Thanks, Wei, for picking up this patch as well as several others of mine.

Michael
diff mbox series

Patch

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index c26ee6fd73c9..8fdccf033b2d 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -1010,8 +1010,6 @@  static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 			goto getmem_done;
 		}
 		pr_info("Unable to allocate enough contiguous physical memory on Gen 1 VM. Using MMIO instead.\n");
-	} else {
-		goto err1;
 	}
 
 	/*