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Date: Wed, 27 Apr 2022 16:30:16 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Juergen Gross <jgross@...e.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>,
"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>
CC: 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>,
KY 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>,
Oleksandr Tyshchenko <olekstysh@...il.com>
Subject: RE: [PATCH v2 2/2] virtio: replace
arch_has_restricted_virtio_memory_access()
From: Juergen Gross <jgross@...e.com> Sent: Wednesday, April 27, 2022 8:34 AM
>
> Instead of using arch_has_restricted_virtio_memory_access() together
> with CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS, replace those
> with platform_has() and a new platform feature
> PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
> V2:
> - move setting of PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS in SEV case
> to sev_setup_arch().
> ---
> 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_amd.c | 4 ++++
> drivers/virtio/Kconfig | 6 ------
> drivers/virtio/virtio.c | 5 ++---
> include/linux/platform-feature.h | 3 ++-
> include/linux/virtio_config.h | 9 ---------
> 10 files changed, 15 insertions(+), 38 deletions(-)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index e084c72104f8..f97a22ae69a8 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -772,7 +772,6 @@ menu "Virtualization"
> config PROTECTED_VIRTUALIZATION_GUEST
> def_bool n
> prompt "Protected virtualization guest support"
> - select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> help
> Select this option, if you want to be able to run this
> kernel as a protected virtualization KVM guest.
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 86ffd0d51fd5..2c3b451813ed 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -31,6 +31,7 @@
> #include <linux/cma.h>
> #include <linux/gfp.h>
> #include <linux/dma-direct.h>
> +#include <linux/platform-feature.h>
> #include <asm/processor.h>
> #include <linux/uaccess.h>
> #include <asm/pgalloc.h>
> @@ -168,22 +169,14 @@ bool force_dma_unencrypted(struct device *dev)
> return is_prot_virt_guest();
> }
>
> -#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> -
> -int arch_has_restricted_virtio_memory_access(void)
> -{
> - return is_prot_virt_guest();
> -}
> -EXPORT_SYMBOL(arch_has_restricted_virtio_memory_access);
> -
> -#endif
> -
> /* protected virtualization */
> static void pv_init(void)
> {
> if (!is_prot_virt_guest())
> return;
>
> + platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> +
> /* make sure bounce buffers are shared */
> swiotlb_force = SWIOTLB_FORCE;
> swiotlb_init(1);
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index b0142e01002e..20ac72546ae4 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1515,7 +1515,6 @@ config X86_CPA_STATISTICS
> config X86_MEM_ENCRYPT
> select ARCH_HAS_FORCE_DMA_UNENCRYPTED
> select DYNAMIC_PHYSICAL_MASK
> - select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> def_bool n
>
> config AMD_MEM_ENCRYPT
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 4b67094215bb..965518b9d14b 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -19,6 +19,7 @@
> #include <linux/i8253.h>
> #include <linux/random.h>
> #include <linux/swiotlb.h>
> +#include <linux/platform-feature.h>
> #include <asm/processor.h>
> #include <asm/hypervisor.h>
> #include <asm/hyperv-tlfs.h>
> @@ -347,8 +348,10 @@ static void __init ms_hyperv_init_platform(void)
> #endif
> /* Isolation VMs are unenlightened SEV-based VMs, thus this check: */
> if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
> - if (hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE)
> + if (hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE) {
> cc_set_vendor(CC_VENDOR_HYPERV);
> +
> platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> + }
> }
> }
>
Unless I'm misunderstanding something, the Hyper-V specific change isn't
needed. Hyper-V doesn't support virtio in the first place, so it's a bit
unexpected be setting a virtio-related flag in Hyper-V code. Also, Hyper-V
guests call sev_setup_arch() with CC_ATTR_GUEST_MEM_ENCRYPT set,
so this virtio-related flag will get set anyway via that path.
Michael
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 50d209939c66..9b6a7c98b2b1 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -76,9 +76,3 @@ void __init mem_encrypt_init(void)
>
> print_mem_encrypt_feature_info();
> }
> -
> -int arch_has_restricted_virtio_memory_access(void)
> -{
> - return cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT);
> -}
> -EXPORT_SYMBOL_GPL(arch_has_restricted_virtio_memory_access);
> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
> index 6169053c2854..39b71084d36b 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -21,6 +21,7 @@
> #include <linux/dma-mapping.h>
> #include <linux/virtio_config.h>
> #include <linux/cc_platform.h>
> +#include <linux/platform-feature.h>
>
> #include <asm/tlbflush.h>
> #include <asm/fixmap.h>
> @@ -206,6 +207,9 @@ void __init sev_setup_arch(void)
> size = total_mem * 6 / 100;
> size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
> swiotlb_adjust_size(size);
> +
> + /* Set restricted memory access for virtio. */
> + platform_set(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
> }
>
> static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index b5adf6abd241..a6dc8b5846fe 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -6,12 +6,6 @@ config VIRTIO
> bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
> or CONFIG_S390_GUEST.
>
> -config ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> - bool
> - help
> - This option is selected if the architecture may need to enforce
> - VIRTIO_F_ACCESS_PLATFORM
> -
> config VIRTIO_PCI_LIB
> tristate
> help
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 22f15f444f75..371e16b18381 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -5,6 +5,7 @@
> #include <linux/module.h>
> #include <linux/idr.h>
> #include <linux/of.h>
> +#include <linux/platform-feature.h>
> #include <uapi/linux/virtio_ids.h>
>
> /* Unique numbering for virtio devices. */
> @@ -170,12 +171,10 @@ EXPORT_SYMBOL_GPL(virtio_add_status);
> static int virtio_features_ok(struct virtio_device *dev)
> {
> unsigned status;
> - int ret;
>
> might_sleep();
>
> - ret = arch_has_restricted_virtio_memory_access();
> - if (ret) {
> + if (platform_has(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS)) {
> if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
> dev_warn(&dev->dev,
> "device must provide VIRTIO_F_VERSION_1\n");
> diff --git a/include/linux/platform-feature.h b/include/linux/platform-feature.h
> index 6ed859928b97..5e2f08554b38 100644
> --- a/include/linux/platform-feature.h
> +++ b/include/linux/platform-feature.h
> @@ -6,7 +6,8 @@
> #include <asm/platform-feature.h>
>
> /* The platform features are starting with the architecture specific ones. */
> -#define PLATFORM_FEAT_N (0 +
> PLATFORM_ARCH_FEAT_N)
> +#define PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS (0 +
> PLATFORM_ARCH_FEAT_N)
> +#define PLATFORM_FEAT_N (1 +
> PLATFORM_ARCH_FEAT_N)
>
> void platform_set(unsigned int feature);
> void platform_clear(unsigned int feature);
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index b341dd62aa4d..79498298519d 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -559,13 +559,4 @@ static inline void virtio_cwrite64(struct virtio_device *vdev,
> _r; \
> })
>
> -#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
> -int arch_has_restricted_virtio_memory_access(void);
> -#else
> -static inline int arch_has_restricted_virtio_memory_access(void)
> -{
> - return 0;
> -}
> -#endif /* CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS */
> -
> #endif /* _LINUX_VIRTIO_CONFIG_H */
> --
> 2.34.1
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