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Date: Mon, 14 Feb 2022 12:41:18 +1000
From: Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v3 03/10] powerpc/pseries/vas: Save LPID in
 pseries_vas_window struct
To: Haren Myneni <haren@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org,
 mpe@ellerman.id.au
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Excerpts from Haren Myneni's message of January 22, 2022 5:55 am:
>=20
> The kernel sets the VAS window with partition PID when is opened in
> the hypervisor. During DLPAR operation, windows can be closed and
> reopened in the hypervisor when the credit is available. So saves
> this PID in pseries_vas_window struct when the window is opened
> initially and reuse it later during DLPAR operation.

This probably shouldn't be called lpid, while you're changing it.
"partition PID" and "LPAR PID" is also confusing. I know the name
somewhat comes from the specifiction, but pid/PID would be fine,
it's clear we are talking about "this LPAR" when in pseries code.

>=20
> Signed-off-by: Haren Myneni <haren@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/vas.c | 7 ++++---
>  arch/powerpc/platforms/pseries/vas.h | 1 +
>  2 files changed, 5 insertions(+), 3 deletions(-)
>=20
> diff --git a/arch/powerpc/platforms/pseries/vas.c
> b/arch/powerpc/platforms/pseries/vas.c
> index d2c8292bfb33..2ef56157634f 100644
> --- a/arch/powerpc/platforms/pseries/vas.c
> +++ b/arch/powerpc/platforms/pseries/vas.c
> @@ -107,7 +107,6 @@ static int h_deallocate_vas_window(u64 winid)
>  static int h_modify_vas_window(struct pseries_vas_window *win)
>  {
>  	long rc;
> -	u32 lpid =3D mfspr(SPRN_PID);
> =20
>  	/*
>  	 * AMR value is not supported in Linux VAS implementation.
> @@ -115,7 +114,7 @@ static int h_modify_vas_window(struct
> pseries_vas_window *win)
>  	 */
>  	do {
>  		rc =3D plpar_hcall_norets(H_MODIFY_VAS_WINDOW,
> -					win->vas_win.winid, lpid, 0,
> +					win->vas_win.winid, win->lpid,
> 0,
>  					VAS_MOD_WIN_FLAGS, 0);
> =20
>  		rc =3D hcall_return_busy_check(rc);
> @@ -125,7 +124,7 @@ static int h_modify_vas_window(struct
> pseries_vas_window *win)
>  		return 0;
> =20
>  	pr_err("H_MODIFY_VAS_WINDOW error: %ld, winid %u lpid %u\n",
> -			rc, win->vas_win.winid, lpid);
> +			rc, win->vas_win.winid, win->lpid);
>  	return -EIO;
>  }
> =20
> @@ -338,6 +337,8 @@ static struct vas_window *vas_allocate_window(int
> vas_id, u64 flags,
>  		}
>  	}
> =20
> +	txwin->lpid =3D mfspr(SPRN_PID);
> +
>  	/*
>  	 * Allocate / Deallocate window hcalls and setup / free IRQs
>  	 * have to be protected with mutex.
> diff --git a/arch/powerpc/platforms/pseries/vas.h
> b/arch/powerpc/platforms/pseries/vas.h
> index fa7ce74f1e49..0538760d13be 100644
> --- a/arch/powerpc/platforms/pseries/vas.h
> +++ b/arch/powerpc/platforms/pseries/vas.h
> @@ -115,6 +115,7 @@ struct pseries_vas_window {
>  	u64 domain[6];		/* Associativity domain Ids */
>  				/* this window is allocated */
>  	u64 util;
> +	u32 lpid;

Comment could be "PID associated with this window".

BTW, is the TID parameter deprecated? Doesn't seem that we use that.

Thanks,
Nick