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Message-ID: <9aa13b10-7342-461c-38a5-eb56d7e69b23@gmail.com>
Date: Wed, 27 Apr 2022 10:48:46 +0300
From: Oleksandr <olekstysh@...il.com>
To: Juergen Gross <jgross@...e.com>
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
x86@...nel.org, linux-s390@...r.kernel.org,
linux-hyperv@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Arnd Bergmann <arnd@...db.de>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 0/2] kernel: add new infrastructure for platform_has()
support
On 26.04.22 16:40, Juergen Gross wrote:
Hello Juergen, all
> 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
I have tested the series on Arm64 in the context of xen-virtio enabling
work. I didn't see any issues with it. Thank you.
I reworked patch #3 [1] to use new functionality:
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index ec5b082..f3b9e20 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -438,6 +438,8 @@ static int __init xen_guest_init(void)
if (!xen_domain())
return 0;
+ xen_set_restricted_virtio_memory_access();
+
if (!acpi_disabled)
xen_acpi_guest_init();
else
diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index 517a9d8..8b71b1d 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -195,6 +195,8 @@ static void __init xen_hvm_guest_init(void)
if (xen_pv_domain())
return;
+ xen_set_restricted_virtio_memory_access();
+
init_hvm_pv_info();
reserve_shared_info();
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 5038edb..fcd5d5d 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -109,6 +109,8 @@ static DEFINE_PER_CPU(struct tls_descs,
shadow_tls_desc);
static void __init xen_pv_init_platform(void)
{
+ xen_set_restricted_virtio_memory_access();
+
populate_extra_pte(fix_to_virt(FIX_PARAVIRT_BOOTMAP));
set_fixmap(FIX_PARAVIRT_BOOTMAP, xen_start_info->shared_info);
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 313a9127..a7bd8ce 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -339,4 +339,15 @@ config XEN_GRANT_DMA_OPS
bool
select DMA_OPS
+config XEN_VIRTIO
+ bool "Xen virtio support"
+ depends on VIRTIO
+ select XEN_GRANT_DMA_OPS
+ help
+ Enable virtio support for running as Xen guest. Depending on the
+ guest type this will require special support on the backend side
+ (qemu or kernel, depending on the virtio device types used).
+
+ If in doubt, say n.
+
endmenu
diff --git a/include/xen/xen.h b/include/xen/xen.h
index a99bab8..e2849c9 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -52,6 +52,14 @@ bool xen_biovec_phys_mergeable(const struct bio_vec
*vec1,
extern u64 xen_saved_max_mem_size;
#endif
+#include <linux/platform-feature.h>
+
+static inline void xen_set_restricted_virtio_memory_access(void)
+{
+ if (IS_ENABLED(CONFIG_XEN_VIRTIO) && xen_domain())
+ platform_set_feature(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
+}
+
#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page
**pages);
void xen_free_unpopulated_pages(unsigned int nr_pages, struct page
**pages);
(END)
[1]
https://lore.kernel.org/lkml/1650646263-22047-4-git-send-email-olekstysh@gmail.com/
>
> 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
>
--
Regards,
Oleksandr Tyshchenko
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