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Message-ID: <alpine.DEB.2.21.1911221159160.11302@sstabellini-ThinkPad-T480s>
Date: Fri, 22 Nov 2019 11:59:29 -0800 (PST)
From: Stefano Stabellini <sstabellini@...nel.org>
To: Pavel Tatashin <pasha.tatashin@...een.com>
cc: jmorris@...ei.org, sashal@...nel.org, linux-kernel@...r.kernel.org,
catalin.marinas@....com, will@...nel.org, steve.capper@....com,
linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
james.morse@....com, vladimir.murzin@....com, mark.rutland@....com,
tglx@...utronix.de, gregkh@...uxfoundation.org,
allison@...utok.net, info@...ux.net, alexios.zavras@...el.com,
sstabellini@...nel.org, boris.ostrovsky@...cle.com,
jgross@...e.com, stefan@...er.ch, yamada.masahiro@...ionext.com,
xen-devel@...ts.xenproject.org, linux@...linux.org.uk
Subject: Re: [PATCH v2 1/3] arm/arm64/xen: use C inlines for privcmd_call
On Thu, 21 Nov 2019, Pavel Tatashin wrote:
> privcmd_call requires to enable access to userspace for the
> duration of the hypercall.
>
> Currently, this is done via assembly macros. Change it to C
> inlines instead.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
I am OK with this.
Acked-by: Stefano Stabellini <sstabellini@...nel.org>
> ---
> arch/arm/include/asm/assembler.h | 2 +-
> arch/arm/include/asm/xen/hypercall.h | 10 +++++++++
> arch/arm/xen/enlighten.c | 2 +-
> arch/arm/xen/hypercall.S | 4 ++--
> arch/arm64/include/asm/xen/hypercall.h | 28 ++++++++++++++++++++++++++
> arch/arm64/xen/hypercall.S | 19 ++---------------
> include/xen/arm/hypercall.h | 12 +++++------
> 7 files changed, 50 insertions(+), 27 deletions(-)
>
> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
> index 99929122dad7..8e9262a0f016 100644
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@ -480,7 +480,7 @@ THUMB( orr \reg , \reg , #PSR_T_BIT )
> .macro uaccess_disable, tmp, isb=1
> #ifdef CONFIG_CPU_SW_DOMAIN_PAN
> /*
> - * Whenever we re-enter userspace, the domains should always be
> + * Whenever we re-enter kernel, the domains should always be
> * set appropriately.
> */
> mov \tmp, #DACR_UACCESS_DISABLE
> diff --git a/arch/arm/include/asm/xen/hypercall.h b/arch/arm/include/asm/xen/hypercall.h
> index 3522cbaed316..cac5bd9ef519 100644
> --- a/arch/arm/include/asm/xen/hypercall.h
> +++ b/arch/arm/include/asm/xen/hypercall.h
> @@ -1 +1,11 @@
> +#ifndef _ASM_ARM_XEN_HYPERCALL_H
> +#define _ASM_ARM_XEN_HYPERCALL_H
> #include <xen/arm/hypercall.h>
> +
> +static inline long privcmd_call(unsigned int call, unsigned long a1,
> + unsigned long a2, unsigned long a3,
> + unsigned long a4, unsigned long a5)
> +{
> + return arch_privcmd_call(call, a1, a2, a3, a4, a5);
> +}
> +#endif /* _ASM_ARM_XEN_HYPERCALL_H */
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index dd6804a64f1a..e87280c6d25d 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -440,4 +440,4 @@ EXPORT_SYMBOL_GPL(HYPERVISOR_platform_op_raw);
> EXPORT_SYMBOL_GPL(HYPERVISOR_multicall);
> EXPORT_SYMBOL_GPL(HYPERVISOR_vm_assist);
> EXPORT_SYMBOL_GPL(HYPERVISOR_dm_op);
> -EXPORT_SYMBOL_GPL(privcmd_call);
> +EXPORT_SYMBOL_GPL(arch_privcmd_call);
> diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S
> index b11bba542fac..277078c7da49 100644
> --- a/arch/arm/xen/hypercall.S
> +++ b/arch/arm/xen/hypercall.S
> @@ -94,7 +94,7 @@ HYPERCALL2(multicall);
> HYPERCALL2(vm_assist);
> HYPERCALL3(dm_op);
>
> -ENTRY(privcmd_call)
> +ENTRY(arch_privcmd_call)
> stmdb sp!, {r4}
> mov r12, r0
> mov r0, r1
> @@ -119,4 +119,4 @@ ENTRY(privcmd_call)
>
> ldm sp!, {r4}
> ret lr
> -ENDPROC(privcmd_call);
> +ENDPROC(arch_privcmd_call);
> diff --git a/arch/arm64/include/asm/xen/hypercall.h b/arch/arm64/include/asm/xen/hypercall.h
> index 3522cbaed316..1a74fb28607f 100644
> --- a/arch/arm64/include/asm/xen/hypercall.h
> +++ b/arch/arm64/include/asm/xen/hypercall.h
> @@ -1 +1,29 @@
> +#ifndef _ASM_ARM64_XEN_HYPERCALL_H
> +#define _ASM_ARM64_XEN_HYPERCALL_H
> #include <xen/arm/hypercall.h>
> +#include <linux/uaccess.h>
> +
> +static inline long privcmd_call(unsigned int call, unsigned long a1,
> + unsigned long a2, unsigned long a3,
> + unsigned long a4, unsigned long a5)
> +{
> + long rv;
> +
> + /*
> + * Privcmd calls are issued by the userspace. The kernel needs to
> + * enable access to TTBR0_EL1 as the hypervisor would issue stage 1
> + * translations to user memory via AT instructions. Since AT
> + * instructions are not affected by the PAN bit (ARMv8.1), we only
> + * need the explicit uaccess_enable/disable if the TTBR0 PAN emulation
> + * is enabled (it implies that hardware UAO and PAN disabled).
> + */
> + uaccess_ttbr0_enable();
> + rv = arch_privcmd_call(call, a1, a2, a3, a4, a5);
> + /*
> + * Disable userspace access from kernel once the hyp call completed.
> + */
> + uaccess_ttbr0_disable();
> +
> + return rv;
> +}
> +#endif /* _ASM_ARM64_XEN_HYPERCALL_H */
> diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S
> index c5f05c4a4d00..921611778d2a 100644
> --- a/arch/arm64/xen/hypercall.S
> +++ b/arch/arm64/xen/hypercall.S
> @@ -49,7 +49,6 @@
>
> #include <linux/linkage.h>
> #include <asm/assembler.h>
> -#include <asm/asm-uaccess.h>
> #include <xen/interface/xen.h>
>
>
> @@ -86,27 +85,13 @@ HYPERCALL2(multicall);
> HYPERCALL2(vm_assist);
> HYPERCALL3(dm_op);
>
> -ENTRY(privcmd_call)
> +ENTRY(arch_privcmd_call)
> mov x16, x0
> mov x0, x1
> mov x1, x2
> mov x2, x3
> mov x3, x4
> mov x4, x5
> - /*
> - * Privcmd calls are issued by the userspace. The kernel needs to
> - * enable access to TTBR0_EL1 as the hypervisor would issue stage 1
> - * translations to user memory via AT instructions. Since AT
> - * instructions are not affected by the PAN bit (ARMv8.1), we only
> - * need the explicit uaccess_enable/disable if the TTBR0 PAN emulation
> - * is enabled (it implies that hardware UAO and PAN disabled).
> - */
> - uaccess_ttbr0_enable x6, x7, x8
> hvc XEN_IMM
> -
> - /*
> - * Disable userspace access from kernel once the hyp call completed.
> - */
> - uaccess_ttbr0_disable x6, x7
> ret
> -ENDPROC(privcmd_call);
> +ENDPROC(arch_privcmd_call);
> diff --git a/include/xen/arm/hypercall.h b/include/xen/arm/hypercall.h
> index b40485e54d80..624c8ad7e42a 100644
> --- a/include/xen/arm/hypercall.h
> +++ b/include/xen/arm/hypercall.h
> @@ -30,8 +30,8 @@
> * IN THE SOFTWARE.
> */
>
> -#ifndef _ASM_ARM_XEN_HYPERCALL_H
> -#define _ASM_ARM_XEN_HYPERCALL_H
> +#ifndef _ARM_XEN_HYPERCALL_H
> +#define _ARM_XEN_HYPERCALL_H
>
> #include <linux/bug.h>
>
> @@ -41,9 +41,9 @@
>
> struct xen_dm_op_buf;
>
> -long privcmd_call(unsigned call, unsigned long a1,
> - unsigned long a2, unsigned long a3,
> - unsigned long a4, unsigned long a5);
> +long arch_privcmd_call(unsigned int call, unsigned long a1,
> + unsigned long a2, unsigned long a3,
> + unsigned long a4, unsigned long a5);
> int HYPERVISOR_xen_version(int cmd, void *arg);
> int HYPERVISOR_console_io(int cmd, int count, char *str);
> int HYPERVISOR_grant_table_op(unsigned int cmd, void *uop, unsigned int count);
> @@ -88,4 +88,4 @@ MULTI_mmu_update(struct multicall_entry *mcl, struct mmu_update *req,
> BUG();
> }
>
> -#endif /* _ASM_ARM_XEN_HYPERCALL_H */
> +#endif /* _ARM_XEN_HYPERCALL_H */
> --
> 2.24.0
>
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