Re: [PATCH v4 1/2] arch/riscv: initial RISC-V support to build/run minimal Xen

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Thu, 2023-01-05 at 18:10 +0200, Oleksii wrote:
> On Thu, 2023-01-05 at 15:48 +0000, Andrew Cooper wrote:
> > On 05/01/2023 1:40 pm, Jan Beulich wrote:
> > > On 05.01.2023 13:01, Oleksii Kurochko wrote:
> > > > To run in debug mode should be done the following instructions:
> > > >  $ qemu-system-riscv64 -M virt -smp 1 -nographic -m 2g \
> > > >         -kernel xen/xen -s -S
> > > >  # In separate terminal:
> > > >  $ riscv64-buildroot-linux-gnu-gdb
> > > >  $ target remote :1234
> > > >  $ add-symbol-file <xen_src>/xen/xen-syms 0x80200000
> > > >  $ hb *0x80200000
> > > >  $ c # it should stop at instruction j 0x80200000 <start>
> > > This suggests to me that Xen is meant to run at VA 0x80200000,
> > > whereas ...
> > > 
> > > > --- a/xen/arch/riscv/include/asm/config.h
> > > > +++ b/xen/arch/riscv/include/asm/config.h
> > > > @@ -1,6 +1,9 @@
> > > >  #ifndef __RISCV_CONFIG_H__
> > > >  #define __RISCV_CONFIG_H__
> > > >  
> > > > +#include <xen/const.h>
> > > > +#include <xen/page-size.h>
> > > > +
> > > >  #if defined(CONFIG_RISCV_64)
> > > >  # define LONG_BYTEORDER 3
> > > >  # define ELFSIZE 64
> > > > @@ -28,7 +31,7 @@
> > > >  
> > > >  /* Linkage for RISCV */
> > > >  #ifdef __ASSEMBLY__
> > > > -#define ALIGN .align 2
> > > > +#define ALIGN .align 4
> > > >  
> > > >  #define ENTRY(name)                                \
> > > >    .globl name;                                     \
> > > > @@ -36,6 +39,10 @@
> > > >    name:
> > > >  #endif
> > > >  
> > > > +#define XEN_VIRT_START  _AT(UL, 0x00200000)
> > > ... here you specify a much lower address (and to be honest even
> > > 0x80200000
> > > looks pretty low to me for 64-bit, and perhaps even for 32-bit).
> > > Could you
> > > clarify what the plans here are? Maybe this is merely a temporary
> > > thing,
> > > but not called out as such?
> > 
> > It's stale from v1 which had:
> > 
> > #define XEN_VIRT_START  0x80200000
Let's switch XEN_VIRT_START to 0x0000000080200000 while we don't have
any MMU support as 0x80200000 is an address where OpenSBI will load
binary (in our case Xen).
> > 
> > 
> > But honestly, I don't think the qemu details in the commit message
> > are
> > useful.  This series is just about making "make build" work.
> > 
> > The next series (being worked on, but not posted yet) is only a few
> > patches and gets a full Gitlab CI smoke test, at which point the
> > smoke
> > test shell script is the reference for how to invoke qemu.
> > 
> > 
> > I'm happy to R-by this series and drop that part of the commit
> > message
> > on commit.
> > 
> I'm happy with that. Thanks.
> > ~Andrew
> 
~ Oleksii