[PATCH v5 0/3] vfio/pci: Restore MMIO access for s390 detached VFs

[PATCH v5 0/3] vfio/pci: Restore MMIO access for s390 detached VFs

[Matthew Rosato]

Changes from v4:
- Switch from dev_flags to a bitfield
- Scrubbed improper use of MSE acronym
- Restored the fixes tag to patch 3 (but the other 2 patches are
  now pre-reqs -- cc stable 5.8?) 

Since commit abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO
access on disabled memory") VFIO now rejects guest MMIO access when the
PCI_COMMAND_MEMORY bit is OFF.  This is however not the case for VFs
(fixed in commit ebfa440ce38b ("vfio/pci: Fix SR-IOV VF handling with
MMIO blocking")).  Furthermore, on s390 where we always run with at
least a bare-metal hypervisor (LPAR) PCI_COMMAND_MEMORY, unlike Device/
Vendor IDs and BARs, is not emulated when VFs are passed-through to the
OS independently.

Based upon Bjorn's most recent comment [1], I investigated the notion of
setting is_virtfn=1 for VFs passed-through to Linux and not linked to a
parent PF (referred to as a 'detached VF' in my prior post).  However,
we rapidly run into issues on how to treat an is_virtfn device with no
linked PF. Further complicating the issue is when you consider the guest
kernel has a passed-through VF but has CONFIG_PCI_IOV=n as in many 
locations is_virtfn checking is ifdef'd out altogether and the device is
assumed to be an independent PCI function.

The decision made by VFIO whether to require or emulate a PCI feature 
(in this case PCI_COMMAND_MEMORY) is based upon the knowledge it has 
about the device, including implicit expectations of what/is not
emulated below VFIO. (ex: is it safe to read vendor/id from config
space?) -- Our firmware layer attempts similar behavior by emulating
things such as vendor/id/BAR access - without these an unlinked VF would
not be usable. But what is or is not emulated by the layer below may be
different based upon which entity is providing the emulation (vfio,
LPAR, some other hypervisor)

So, the proposal here aims to fix the immediate issue of s390
pass-through VFs becoming suddenly unusable by vfio by using a new 
bit to identify a VF feature that we know is hardwired to 0 for any
VF (PCI_COMMAND_MEMORY) and de-coupling the need for emulating
PCI_COMMAND_MEMORY from the is_virtfn flag. The exact scope of is_virtfn
and physfn for bare-metal vs guest scenarios and identifying what
features are / are not emulated by the lower-level hypervisors is a much
bigger discussion independent of this limited proposal.

[1]: https://marc.info/?l=linux-pci&m=159856041930022&w=2



Matthew Rosato (3):
  PCI/IOV: Mark VFs as not implementing PCI_COMMAND_MEMORY
  s390/pci: Mark all VFs as not implementing PCI_COMMAND_MEMORY
  vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

 arch/s390/pci/pci_bus.c            |  5 +++--
 drivers/pci/iov.c                  |  1 +
 drivers/vfio/pci/vfio_pci_config.c | 24 ++++++++++++++----------
 include/linux/pci.h                |  1 +
 4 files changed, 19 insertions(+), 12 deletions(-)

-- 
1.8.3.1

[PATCH v5 1/3] PCI/IOV: Mark VFs as not implementing PCI_COMMAND_MEMORY

[Matthew Rosato]

For VFs, the Memory Space Enable bit in the Command Register is
hard-wired to 0.

Add a new bit to signify devices where the Command Register Memory
Space Enable bit does not control the device's response to MMIO
accesses.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 drivers/pci/iov.c   | 1 +
 include/linux/pci.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index b37e08c..4afd4ee 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -180,6 +180,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
 	virtfn->device = iov->vf_device;
 	virtfn->is_virtfn = 1;
 	virtfn->physfn = pci_dev_get(dev);
+	virtfn->no_command_memory = 1;
 
 	if (id == 0)
 		pci_read_vf_config_common(virtfn);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8355306..3ff72312 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -445,6 +445,7 @@ struct pci_dev {
 	unsigned int	is_probed:1;		/* Device probing in progress */
 	unsigned int	link_active_reporting:1;/* Device capable of reporting link active */
 	unsigned int	no_vf_scan:1;		/* Don't scan for VFs after IOV enablement */
+	unsigned int	no_command_memory:1;	/* No PCI_COMMAND_MEMORY */
 	pci_dev_flags_t dev_flags;
 	atomic_t	enable_cnt;	/* pci_enable_device has been called */
 
-- 
1.8.3.1

[PATCH v5 2/3] s390/pci: Mark all VFs as not implementing PCI_COMMAND_MEMORY

[Matthew Rosato]

For s390 we can have VFs that are passed-through without the associated
PF. Firmware provides an emulation layer to allow these devices to
operate independently, but is missing emulation of the Memory Space
Enable bit.  For these as well as linked VFs, set no_command_memory
which specifies these devices do not implement PCI_COMMAND_MEMORY.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
---
 arch/s390/pci/pci_bus.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
index 5967f30..c93486a 100644
--- a/arch/s390/pci/pci_bus.c
+++ b/arch/s390/pci/pci_bus.c
@@ -197,9 +197,10 @@ void pcibios_bus_add_device(struct pci_dev *pdev)
 	 * With pdev->no_vf_scan the common PCI probing code does not
 	 * perform PF/VF linking.
 	 */
-	if (zdev->vfn)
+	if (zdev->vfn) {
 		zpci_bus_setup_virtfn(zdev->zbus, pdev, zdev->vfn);
-
+		pdev->no_command_memory = 1;
+	}
 }
 
 static int zpci_bus_add_device(struct zpci_bus *zbus, struct zpci_dev *zdev)
-- 
1.8.3.1

[PATCH v5 3/3] vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

[Matthew Rosato]

While it is true that devices with is_virtfn=1 will have a Memory Space
Enable bit that is hard-wired to 0, this is not the only case where we
see this behavior -- For example some bare-metal hypervisors lack
Memory Space Enable bit emulation for devices not setting is_virtfn
(s390). Fix this by instead checking for the newly-added
no_command_memory bit which directly denotes the need for
PCI_COMMAND_MEMORY emulation in vfio.

Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
---
 drivers/vfio/pci/vfio_pci_config.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index d98843f..5076d01 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -406,7 +406,7 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev)
 	 * PF SR-IOV capability, there's therefore no need to trigger
 	 * faults based on the virtual value.
 	 */
-	return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY);
+	return pdev->no_command_memory || (cmd & PCI_COMMAND_MEMORY);
 }
 
 /*
@@ -520,8 +520,8 @@ static int vfio_basic_config_read(struct vfio_pci_device *vdev, int pos,
 
 	count = vfio_default_config_read(vdev, pos, count, perm, offset, val);
 
-	/* Mask in virtual memory enable for SR-IOV devices */
-	if (offset == PCI_COMMAND && vdev->pdev->is_virtfn) {
+	/* Mask in virtual memory enable */
+	if (offset == PCI_COMMAND && vdev->pdev->no_command_memory) {
 		u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);
 		u32 tmp_val = le32_to_cpu(*val);
 
@@ -589,9 +589,11 @@ static int vfio_basic_config_write(struct vfio_pci_device *vdev, int pos,
 		 * shows it disabled (phys_mem/io, then the device has
 		 * undergone some kind of backdoor reset and needs to be
 		 * restored before we allow it to enable the bars.
-		 * SR-IOV devices will trigger this, but we catch them later
+		 * SR-IOV devices will trigger this - for mem enable let's
+		 * catch this now and for io enable it will be caught later
 		 */
-		if ((new_mem && virt_mem && !phys_mem) ||
+		if ((new_mem && virt_mem && !phys_mem &&
+		     !pdev->no_command_memory) ||
 		    (new_io && virt_io && !phys_io) ||
 		    vfio_need_bar_restore(vdev))
 			vfio_bar_restore(vdev);
@@ -1734,12 +1736,14 @@ int vfio_config_init(struct vfio_pci_device *vdev)
 				 vconfig[PCI_INTERRUPT_PIN]);
 
 		vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
-
+	}
+	if (pdev->no_command_memory) {
 		/*
-		 * VFs do no implement the memory enable bit of the COMMAND
-		 * register therefore we'll not have it set in our initial
-		 * copy of config space after pci_enable_device().  For
-		 * consistency with PFs, set the virtual enable bit here.
+		 * VFs and devices that set pdev->no_command_memory do not
+		 * implement the memory enable bit of the COMMAND register
+		 * therefore we'll not have it set in our initial copy of
+		 * config space after pci_enable_device().  For consistency
+		 * with PFs, set the virtual enable bit here.
 		 */
 		*(__le16 *)&vconfig[PCI_COMMAND] |=
 					cpu_to_le16(PCI_COMMAND_MEMORY);
-- 
1.8.3.1

Re: [PATCH v5 1/3] PCI/IOV: Mark VFs as not implementing PCI_COMMAND_MEMORY

[Bjorn Helgaas]

On Thu, Sep 10, 2020 at 10:59:55AM -0400, Matthew Rosato wrote:
> For VFs, the Memory Space Enable bit in the Command Register is
> hard-wired to 0.
> 
> Add a new bit to signify devices where the Command Register Memory
> Space Enable bit does not control the device's response to MMIO
> accesses.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/pci/iov.c   | 1 +
>  include/linux/pci.h | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index b37e08c..4afd4ee 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -180,6 +180,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  	virtfn->device = iov->vf_device;
>  	virtfn->is_virtfn = 1;
>  	virtfn->physfn = pci_dev_get(dev);
> +	virtfn->no_command_memory = 1;
>  
>  	if (id == 0)
>  		pci_read_vf_config_common(virtfn);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 8355306..3ff72312 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -445,6 +445,7 @@ struct pci_dev {
>  	unsigned int	is_probed:1;		/* Device probing in progress */
>  	unsigned int	link_active_reporting:1;/* Device capable of reporting link active */
>  	unsigned int	no_vf_scan:1;		/* Don't scan for VFs after IOV enablement */
> +	unsigned int	no_command_memory:1;	/* No PCI_COMMAND_MEMORY */
>  	pci_dev_flags_t dev_flags;
>  	atomic_t	enable_cnt;	/* pci_enable_device has been called */
>  
> -- 
> 1.8.3.1
> 

Re: [PATCH v5 3/3] vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

[Matthew Rosato]

On 9/10/20 10:59 AM, Matthew Rosato wrote:
> While it is true that devices with is_virtfn=1 will have a Memory Space
> Enable bit that is hard-wired to 0, this is not the only case where we
> see this behavior -- For example some bare-metal hypervisors lack
> Memory Space Enable bit emulation for devices not setting is_virtfn
> (s390). Fix this by instead checking for the newly-added
> no_command_memory bit which directly denotes the need for
> PCI_COMMAND_MEMORY emulation in vfio.
> 
> Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>

Polite ping on this patch as the other 2 have now received maintainer 
ACKs or reviews.  I'm concerned about this popping up in distros as 
abafbc551fdd was a CVE fix.  Related, see question from the cover:

- Restored the fixes tag to patch 3 (but the other 2 patches are
   now pre-reqs -- cc stable 5.8?)

Thanks,
Matt

> ---
>   drivers/vfio/pci/vfio_pci_config.c | 24 ++++++++++++++----------
>   1 file changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> index d98843f..5076d01 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -406,7 +406,7 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev)
>   	 * PF SR-IOV capability, there's therefore no need to trigger
>   	 * faults based on the virtual value.
>   	 */
> -	return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY);
> +	return pdev->no_command_memory || (cmd & PCI_COMMAND_MEMORY);
>   }
>   
>   /*
> @@ -520,8 +520,8 @@ static int vfio_basic_config_read(struct vfio_pci_device *vdev, int pos,
>   
>   	count = vfio_default_config_read(vdev, pos, count, perm, offset, val);
>   
> -	/* Mask in virtual memory enable for SR-IOV devices */
> -	if (offset == PCI_COMMAND && vdev->pdev->is_virtfn) {
> +	/* Mask in virtual memory enable */
> +	if (offset == PCI_COMMAND && vdev->pdev->no_command_memory) {
>   		u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);
>   		u32 tmp_val = le32_to_cpu(*val);
>   
> @@ -589,9 +589,11 @@ static int vfio_basic_config_write(struct vfio_pci_device *vdev, int pos,
>   		 * shows it disabled (phys_mem/io, then the device has
>   		 * undergone some kind of backdoor reset and needs to be
>   		 * restored before we allow it to enable the bars.
> -		 * SR-IOV devices will trigger this, but we catch them later
> +		 * SR-IOV devices will trigger this - for mem enable let's
> +		 * catch this now and for io enable it will be caught later
>   		 */
> -		if ((new_mem && virt_mem && !phys_mem) ||
> +		if ((new_mem && virt_mem && !phys_mem &&
> +		     !pdev->no_command_memory) ||
>   		    (new_io && virt_io && !phys_io) ||
>   		    vfio_need_bar_restore(vdev))
>   			vfio_bar_restore(vdev);
> @@ -1734,12 +1736,14 @@ int vfio_config_init(struct vfio_pci_device *vdev)
>   				 vconfig[PCI_INTERRUPT_PIN]);
>   
>   		vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
> -
> +	}
> +	if (pdev->no_command_memory) {
>   		/*
> -		 * VFs do no implement the memory enable bit of the COMMAND
> -		 * register therefore we'll not have it set in our initial
> -		 * copy of config space after pci_enable_device().  For
> -		 * consistency with PFs, set the virtual enable bit here.
> +		 * VFs and devices that set pdev->no_command_memory do not
> +		 * implement the memory enable bit of the COMMAND register
> +		 * therefore we'll not have it set in our initial copy of
> +		 * config space after pci_enable_device().  For consistency
> +		 * with PFs, set the virtual enable bit here.
>   		 */
>   		*(__le16 *)&vconfig[PCI_COMMAND] |=
>   					cpu_to_le16(PCI_COMMAND_MEMORY);
> 

Re: [PATCH v5 3/3] vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

[Alex Williamson]

On Mon, 21 Sep 2020 08:43:29 -0400
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> On 9/10/20 10:59 AM, Matthew Rosato wrote:
> > While it is true that devices with is_virtfn=1 will have a Memory Space
> > Enable bit that is hard-wired to 0, this is not the only case where we
> > see this behavior -- For example some bare-metal hypervisors lack
> > Memory Space Enable bit emulation for devices not setting is_virtfn
> > (s390). Fix this by instead checking for the newly-added
> > no_command_memory bit which directly denotes the need for
> > PCI_COMMAND_MEMORY emulation in vfio.
> > 
> > Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
> > Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> > Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>  
> 
> Polite ping on this patch as the other 2 have now received maintainer 
> ACKs or reviews.  I'm concerned about this popping up in distros as 
> abafbc551fdd was a CVE fix.  Related, see question from the cover:
> 
> - Restored the fixes tag to patch 3 (but the other 2 patches are
>    now pre-reqs -- cc stable 5.8?)

I've got these queued in my local branch which I'll push to next for
v5.10.  I'm thinking that perhaps the right thing would be to add the
fixes tag to all three patches, otherwise I could see that the PCI/VF
change might get picked as a dependency, but not the s390 specific one.
Does this sound correct to everyone?  Thanks,

Alex

> > ---
> >   drivers/vfio/pci/vfio_pci_config.c | 24 ++++++++++++++----------
> >   1 file changed, 14 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> > index d98843f..5076d01 100644
> > --- a/drivers/vfio/pci/vfio_pci_config.c
> > +++ b/drivers/vfio/pci/vfio_pci_config.c
> > @@ -406,7 +406,7 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev)
> >   	 * PF SR-IOV capability, there's therefore no need to trigger
> >   	 * faults based on the virtual value.
> >   	 */
> > -	return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY);
> > +	return pdev->no_command_memory || (cmd & PCI_COMMAND_MEMORY);
> >   }
> >   
> >   /*
> > @@ -520,8 +520,8 @@ static int vfio_basic_config_read(struct vfio_pci_device *vdev, int pos,
> >   
> >   	count = vfio_default_config_read(vdev, pos, count, perm, offset, val);
> >   
> > -	/* Mask in virtual memory enable for SR-IOV devices */
> > -	if (offset == PCI_COMMAND && vdev->pdev->is_virtfn) {
> > +	/* Mask in virtual memory enable */
> > +	if (offset == PCI_COMMAND && vdev->pdev->no_command_memory) {
> >   		u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);
> >   		u32 tmp_val = le32_to_cpu(*val);
> >   
> > @@ -589,9 +589,11 @@ static int vfio_basic_config_write(struct vfio_pci_device *vdev, int pos,
> >   		 * shows it disabled (phys_mem/io, then the device has
> >   		 * undergone some kind of backdoor reset and needs to be
> >   		 * restored before we allow it to enable the bars.
> > -		 * SR-IOV devices will trigger this, but we catch them later
> > +		 * SR-IOV devices will trigger this - for mem enable let's
> > +		 * catch this now and for io enable it will be caught later
> >   		 */
> > -		if ((new_mem && virt_mem && !phys_mem) ||
> > +		if ((new_mem && virt_mem && !phys_mem &&
> > +		     !pdev->no_command_memory) ||
> >   		    (new_io && virt_io && !phys_io) ||
> >   		    vfio_need_bar_restore(vdev))
> >   			vfio_bar_restore(vdev);
> > @@ -1734,12 +1736,14 @@ int vfio_config_init(struct vfio_pci_device *vdev)
> >   				 vconfig[PCI_INTERRUPT_PIN]);
> >   
> >   		vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
> > -
> > +	}
> > +	if (pdev->no_command_memory) {
> >   		/*
> > -		 * VFs do no implement the memory enable bit of the COMMAND
> > -		 * register therefore we'll not have it set in our initial
> > -		 * copy of config space after pci_enable_device().  For
> > -		 * consistency with PFs, set the virtual enable bit here.
> > +		 * VFs and devices that set pdev->no_command_memory do not
> > +		 * implement the memory enable bit of the COMMAND register
> > +		 * therefore we'll not have it set in our initial copy of
> > +		 * config space after pci_enable_device().  For consistency
> > +		 * with PFs, set the virtual enable bit here.
> >   		 */
> >   		*(__le16 *)&vconfig[PCI_COMMAND] |=
> >   					cpu_to_le16(PCI_COMMAND_MEMORY);
> >   
> 

Re: [PATCH v5 3/3] vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

[Matthew Rosato]

On 9/22/20 12:40 PM, Alex Williamson wrote:
> On Mon, 21 Sep 2020 08:43:29 -0400
> Matthew Rosato <mjrosato@linux.ibm.com> wrote:
> 
>> On 9/10/20 10:59 AM, Matthew Rosato wrote:
>>> While it is true that devices with is_virtfn=1 will have a Memory Space
>>> Enable bit that is hard-wired to 0, this is not the only case where we
>>> see this behavior -- For example some bare-metal hypervisors lack
>>> Memory Space Enable bit emulation for devices not setting is_virtfn
>>> (s390). Fix this by instead checking for the newly-added
>>> no_command_memory bit which directly denotes the need for
>>> PCI_COMMAND_MEMORY emulation in vfio.
>>>
>>> Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
>>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>>> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
>>> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
>>
>> Polite ping on this patch as the other 2 have now received maintainer
>> ACKs or reviews.  I'm concerned about this popping up in distros as
>> abafbc551fdd was a CVE fix.  Related, see question from the cover:
>>
>> - Restored the fixes tag to patch 3 (but the other 2 patches are
>>     now pre-reqs -- cc stable 5.8?)
> 
> I've got these queued in my local branch which I'll push to next for
> v5.10.  I'm thinking that perhaps the right thing would be to add the
> fixes tag to all three patches, otherwise I could see that the PCI/VF
> change might get picked as a dependency, but not the s390 specific one.
> Does this sound correct to everyone?  Thanks,

Sounds good to me.  Thanks!

Re: [PATCH v5 3/3] vfio/pci: Decouple PCI_COMMAND_MEMORY bit checks from is_virtfn

[Pierre Morel]

On 2020-09-22 18:40, Alex Williamson wrote:
> On Mon, 21 Sep 2020 08:43:29 -0400
> Matthew Rosato <mjrosato@linux.ibm.com> wrote:
> 
>> On 9/10/20 10:59 AM, Matthew Rosato wrote:
>>> While it is true that devices with is_virtfn=1 will have a Memory Space
>>> Enable bit that is hard-wired to 0, this is not the only case where we
>>> see this behavior -- For example some bare-metal hypervisors lack
>>> Memory Space Enable bit emulation for devices not setting is_virtfn
>>> (s390). Fix this by instead checking for the newly-added
>>> no_command_memory bit which directly denotes the need for
>>> PCI_COMMAND_MEMORY emulation in vfio.
>>>
>>> Fixes: abafbc551fdd ("vfio-pci: Invalidate mmaps and block MMIO access on disabled memory")
>>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>>> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
>>> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
>>
>> Polite ping on this patch as the other 2 have now received maintainer
>> ACKs or reviews.  I'm concerned about this popping up in distros as
>> abafbc551fdd was a CVE fix.  Related, see question from the cover:
>>
>> - Restored the fixes tag to patch 3 (but the other 2 patches are
>>     now pre-reqs -- cc stable 5.8?)
> 
> I've got these queued in my local branch which I'll push to next for
> v5.10.  I'm thinking that perhaps the right thing would be to add the
> fixes tag to all three patches, otherwise I could see that the PCI/VF
> change might get picked as a dependency, but not the s390 specific one.
> Does this sound correct to everyone?  Thanks,
> 
> Alex
> 
sound correct for me.
Thanks.

Pierre

-- 
Pierre Morel
IBM Lab Boeblingen