Re: [PATCH v3 30/52] xen/mpu: populate a new region in Xen MPU mapping table

[Penny Zheng <penny.zheng@xxxxxxx>]

Hi Ayan

On 2023/6/28 18:08, Ayan Kumar Halder wrote:
> (Forgot to cc)
>
> On 28/06/2023 11:05, Ayan Kumar Halder wrote:
> > Hi Penny,
> >
> > On 26/06/2023 04:34, Penny Zheng wrote:
> > > CAUTION: This message has originated from an External Source. Please 
> > > use proper judgment and caution when opening attachments, clicking 
> > > links, or responding to this email.
> > >
> > > The new helper xen_mpumap_update() is responsible for updating Xen 
> > > MPU memory
> > > mapping table(xen_mpumap), including creating a new entry, updating
> > > or destroying an existing one. It is equivalent to xen_pt_update in MMU.
> > > This commit only talks about populating a new entry in Xen MPU memory 
> > > mapping
> > > table(xen_mpumap). Others will be introduced in the following commits.
> > >
> > > When populating a new entry in Xen MPU memory mapping table(xen_mpumap),
> > > firstly, we shall check if requested address range [base, limit) is 
> > > mapped.
> > > If not, we shall find a free slot in xen_mpumap to insert, based on 
> > > bitmap
> > > xen_mpumap_mask, and use standard entry pr_of_xenaddr() to build up 
> > > MPU memory
> > > region structure(pr_t)
> > > In the last, we set memory attribute and permission based on variable 
> > > @flags.
> > > To summarize all region attributes in one variable @flags, layout of the
> > > flags is elaborated as follows:
> > > [0:2] Memory attribute Index
> > > [3:4] Execute Never
> > > [5:6] Access Permission
> > > [7]   Region Present
> > > Also, we provide a set of definitions(REGION_HYPERVISOR_RW, etc) that 
> > > combine
> > > the memory attribute and permission for common combinations.
> > >
> > > Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> > > Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> > > ---
> > > v3:
> > > - implement pr_set_base/pr_set_limit/region_is_valid using static
> > > inline.
> > > - define index uint8_t to limit its size
> > > - stay the same major entry map_pages_to_xen, then go different path
> > > in different context(xen_pt_update in MMU, and xen_mpumap_update in MPU)
> > > ---
> > >   xen/arch/arm/include/asm/arm64/mpu.h |  64 +++++++
> > >   xen/arch/arm/include/asm/mm.h        |   3 +
> > >   xen/arch/arm/include/asm/mpu/mm.h    |  16 ++
> > >   xen/arch/arm/include/asm/page.h      |  22 +++
> > >   xen/arch/arm/mm.c                    |  20 +++
> > >   xen/arch/arm/mmu/mm.c                |   9 +-
> > >   xen/arch/arm/mpu/mm.c                | 255 +++++++++++++++++++++++++++
> > >   7 files changed, 381 insertions(+), 8 deletions(-)
> > >   create mode 100644 xen/arch/arm/include/asm/mpu/mm.h
> > >
> > > diff --git a/xen/arch/arm/include/asm/arm64/mpu.h 
> > > b/xen/arch/arm/include/asm/arm64/mpu.h
> > > index 407fec66c9..a6b07bab02 100644
> > > --- a/xen/arch/arm/include/asm/arm64/mpu.h
> > > +++ b/xen/arch/arm/include/asm/arm64/mpu.h
> > > @@ -6,6 +6,10 @@
> > >   #ifndef __ARM64_MPU_H__
> > >   #define __ARM64_MPU_H__
> > >
> > > +#define MPU_REGION_SHIFT  6
> > You are using this macro in patch 24/52 and you are defining it here.
> >
> > Please consider moving the definition to patch 24/52.
Thanks for pointing out. I'll move.

> > > +#define MPU_REGION_ALIGN  (_AC(1, UL) << MPU_REGION_SHIFT)
> > > +#define MPU_REGION_MASK   (~(MPU_REGION_ALIGN - 1))
> > > +
> > >   /*
> > >    * MPUIR_EL2.Region identifies the number of regions supported by 
> > > the EL2 MPU.
> > >    * It is a 8-bit field, so 255 MPU memory regions at most.
> > > @@ -21,8 +25,33 @@
> > >   #define REGION_UART_SEL            0x07
> > >   #define MPUIR_REGION_MASK          ((_AC(1, UL) << 8) - 1)
...
> > > +static inline bool region_is_valid(pr_t *pr)
> > > +{
> > > +    return pr->prlar.reg.en;
> > > +}
> > A lot of these macros and inlines can be reused on arm32 as well. I 
> > have split them as follows :-
> > Refer 
> > https://github.com/Xilinx/xen/blob/xlnx_rebase_4.17/xen/arch/arm_mpu/include/asm/armv8r/mpu.h for the common definitions.
> > Refer 
> > https://github.com/Xilinx/xen/blob/xlnx_rebase_4.17/xen/arch/arm_mpu/include/asm/armv8r/arm64/mpu.h for the 64 bit specific definitions
> > Refer 
> > https://github.com/Xilinx/xen/blob/xlnx_rebase_4.17/xen/arch/arm_mpu/include/asm/armv8r/arm32/mpu.h for the 32 bit specific definitions (This I can add later as part of R52 port).
> > Please consider splitting the definitions so that R52 can reuse the 
> > common ones.
Sure. I'll try to split.

> > - Ayan