[v3,0/2] Add API for making parts of a MMIO page R/O and use it in XHCI console

Message

Marek Marczykowski-Górecki May 21, 2024, 2:54 a.m. UTC

On older systems, XHCI xcap had a layout that no other (interesting) registers
were placed on the same page as the debug capability, so Linux was fine with
making the whole page R/O. But at least on Tiger Lake and Alder Lake, Linux
needs to write to some other registers on the same page too.

Add a generic API for making just parts of an MMIO page R/O and use it to fix
USB3 console with share=yes or share=hwdom options. More details in commit
messages.

Technically it may still qualify for 4.19, since v1 was sent well before
last posting date. But I realize it's quite late and it isn't top
priority series, so if it won't hit 4.19, it's okay with me too.

Marek Marczykowski-Górecki (2):
  x86/mm: add API for marking only part of a MMIO page read only
  drivers/char: Use sub-page ro API to make just xhci dbc cap RO

 xen/arch/x86/hvm/emulate.c      |   2 +-
 xen/arch/x86/hvm/hvm.c          |   8 +-
 xen/arch/x86/include/asm/mm.h   |  18 ++-
 xen/arch/x86/mm.c               | 268 +++++++++++++++++++++++++++++++++-
 xen/arch/x86/pv/ro-page-fault.c |   1 +-
 xen/drivers/char/xhci-dbc.c     |  27 +--
 6 files changed, 309 insertions(+), 15 deletions(-)

base-commit: b0082b908391b29b7c4dd5e6c389ebd6481926f8

Comments

Jan Beulich May 22, 2024, 8:07 a.m. UTC | #1

On 21.05.2024 04:54, Marek Marczykowski-Górecki wrote:
> On older systems, XHCI xcap had a layout that no other (interesting) registers
> were placed on the same page as the debug capability, so Linux was fine with
> making the whole page R/O. But at least on Tiger Lake and Alder Lake, Linux
> needs to write to some other registers on the same page too.
> 
> Add a generic API for making just parts of an MMIO page R/O and use it to fix
> USB3 console with share=yes or share=hwdom options. More details in commit
> messages.
> 
> Technically it may still qualify for 4.19, since v1 was sent well before
> last posting date. But I realize it's quite late and it isn't top
> priority series, so if it won't hit 4.19, it's okay with me too.
> 
> Marek Marczykowski-Górecki (2):
>   x86/mm: add API for marking only part of a MMIO page read only
>   drivers/char: Use sub-page ro API to make just xhci dbc cap RO
> 
>  xen/arch/x86/hvm/emulate.c      |   2 +-
>  xen/arch/x86/hvm/hvm.c          |   8 +-
>  xen/arch/x86/include/asm/mm.h   |  18 ++-
>  xen/arch/x86/mm.c               | 268 +++++++++++++++++++++++++++++++++-
>  xen/arch/x86/pv/ro-page-fault.c |   1 +-
>  xen/drivers/char/xhci-dbc.c     |  27 +--
>  6 files changed, 309 insertions(+), 15 deletions(-)

Just to mention it here again, with v2 having been quite some time ago:
Like for that other work of yours I'm not really convinced the complexity
is worth the gain. Ultimately this may once again mean that I'll demand
a 2nd maintainer's ack, once technically I may be okay to offer R-b.

Jan