[PATCH 0/2] kernel: add new infrastructure for platform_has() support

From: Juergen Gross via Virtualization <virtualization@lists.linux-foundation.org>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	x86@kernel.org, linux-s390@vger.kernel.org,
	linux-hyperv@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Wei Liu <wei.liu@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Dexuan Cui <decui@microsoft.com>,
	Christoph Hellwig <hch@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Arnd Bergmann <arnd@arndb.de>, Heiko Carstens <hca@linux.ibm.com>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juergen Gross <jgross@suse.com>,
	Oleksandr Tyshchenko <olekstysh@gmail.com>,
	Sven Schnelle <svens@linux.ibm.com>
Subject: [PATCH 0/2] kernel: add new infrastructure for platform_has() support
Date: Tue, 26 Apr 2022 15:40:19 +0200	[thread overview]
Message-ID: <20220426134021.11210-1-jgross@suse.com> (raw)

In another patch series [1] the need has come up to have support for
a generic feature flag infrastructure.

This patch series is introducing that infrastructure and adds the first
use case.

I have decided to use a similar interface as the already known x86
cpu_has() function. As the new infrastructure is meant to be usable for
general and arch-specific feature flags, the flags are being spread
between a general bitmap and an arch specific one.

The bitmaps start all being zero, single features can be set or reset
at any time by using the related platform_[re]set_feature() functions.

The platform_has() function is using a simple test_bit() call for now,
further optimization might be added when needed.

[1]: https://lore.kernel.org/lkml/1650646263-22047-1-git-send-email-olekstysh@gmail.com/T/#t

Juergen Gross (2):
  kernel: add platform_has() infrastructure
  virtio: replace arch_has_restricted_virtio_memory_access()

 MAINTAINERS                            |  8 +++++++
 arch/s390/Kconfig                      |  1 -
 arch/s390/mm/init.c                    | 13 +++--------
 arch/x86/Kconfig                       |  1 -
 arch/x86/kernel/cpu/mshyperv.c         |  5 ++++-
 arch/x86/mm/mem_encrypt.c              |  6 ------
 arch/x86/mm/mem_encrypt_identity.c     |  5 +++++
 drivers/virtio/Kconfig                 |  6 ------
 drivers/virtio/virtio.c                |  5 ++---
 include/asm-generic/Kbuild             |  1 +
 include/asm-generic/platform-feature.h |  8 +++++++
 include/linux/platform-feature.h       | 30 ++++++++++++++++++++++++++
 include/linux/virtio_config.h          |  9 --------
 kernel/Makefile                        |  2 +-
 kernel/platform-feature.c              |  7 ++++++
 15 files changed, 69 insertions(+), 38 deletions(-)
 create mode 100644 include/asm-generic/platform-feature.h
 create mode 100644 include/linux/platform-feature.h
 create mode 100644 kernel/platform-feature.c

-- 
2.34.1

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