linux-kernel - Re: [PATCH v8 23/30] KVM: selftests: Add functions to allow mapping as shared

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Message-ID: <689a3b296261c_1d882b294ed@iweiny-mobl.notmuch>
Date: Mon, 11 Aug 2025 13:49:13 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Sagi Shahar <sagis@...gle.com>, <linux-kselftest@...r.kernel.org>, "Paolo
 Bonzini" <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, "Sean
 Christopherson" <seanjc@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>,
	Ryan Afranji <afranji@...gle.com>, Andrew Jones <ajones@...tanamicro.com>,
	Isaku Yamahata <isaku.yamahata@...el.com>, Erdem Aktas
	<erdemaktas@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, "Roger
 Wang" <runanwang@...gle.com>, Binbin Wu <binbin.wu@...ux.intel.com>, "Oliver
 Upton" <oliver.upton@...ux.dev>, "Pratik R. Sampat"
	<pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>,
	Ira Weiny <ira.weiny@...el.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v8 23/30] KVM: selftests: Add functions to allow mapping
 as shared

Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@...gle.com>
> 
> virt_map() enforces a private mapping for private memory. Introduce
> virt_map_shared() that creates a shared mapping for private as
> well as shared memory. This way, the TD does not have to remap its
> page tables at runtime.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> Signed-off-by: Sagi Shahar <sagis@...gle.com>
> ---
>  .../testing/selftests/kvm/include/kvm_util.h  | 23 +++++++++++++
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 34 +++++++++++++++++++
>  .../testing/selftests/kvm/lib/x86/processor.c | 15 ++++++--
>  3 files changed, 70 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 0d1f24c9f7c7..2e444c172261 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h

[snip]

> +/*
> + * VM Virtual Page Map as Shared
> + *
> + * Input Args:
> + *   vm - Virtual Machine
> + *   vaddr - VM Virtual Address
> + *   paddr - VM Physical Address
> + *
> + * Output Args: None
> + *
> + * Return: None
> + *
> + * Within @vm, creates a virtual translation for the page starting
> + * at @vaddr to the page starting at @paddr.
> + */
> +void virt_arch_pg_map_shared(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr);
> +
> +static inline void virt_pg_map_shared(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
> +{
> +	virt_arch_pg_map_shared(vm, vaddr, paddr);
> +}
>  
>  /*
>   * Address Guest Virtual to Guest Physical

[snip]

> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index 3977719c7893..7742c01d48b1 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -181,7 +181,8 @@ static uint64_t *virt_create_upper_pte(struct kvm_vm *vm,
>  	return pte;
>  }
>  

[snip]

>  void virt_arch_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
>  {
>  	__virt_pg_map(vm, vaddr, paddr, PG_LEVEL_4K);
>  }
>  
> +void virt_arch_pg_map_shared(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
> +{
> +	___virt_pg_map(vm, vaddr, paddr, PG_LEVEL_4K, false);
> +}

What about non-x86 arch'es?  How does this compile for them?

Ira

> +
>  void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
>  		    uint64_t nr_bytes, int level)
>  {
> -- 
> 2.51.0.rc0.155.g4a0f42376b-goog
>