Subject: Re: [RFC PATCH 12/45] KVM: arm64: pkvm: Unify pkvm_pkvm_teardown_donated_memory()

From: Sebastian Ene <[email-masked]>
Date: Mon, 15 Jan 2024 14:33:50 +0000

On Wed, Feb 01, 2023 at 12:52:56PM +0000, Jean-Philippe Brucker wrote:

Hi Jean,

> Tearing down donated memory requires clearing the memory, pushing the
> pages into the reclaim memcache, and moving the mapping into the host
> stage-2. Keep these operations in a single function.
> 
> Signed-off-by: Jean-Philippe Brucker <[email-masked]>
> ---
>  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  2 +
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c         |  3 +-
>  arch/arm64/kvm/hyp/nvhe/pkvm.c                | 50 +++++++------------
>  3 files changed, 22 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> index d4f4ffbb7dbb..021825aee854 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> @@ -86,6 +86,8 @@ void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc);
>  
>  void *pkvm_map_donated_memory(unsigned long host_va, size_t size);
>  void pkvm_unmap_donated_memory(void *va, size_t size);
> +void pkvm_teardown_donated_memory(struct kvm_hyp_memcache *mc, void *addr,
> +				  size_t dirty_size);
>  
>  static __always_inline void __load_host_stage2(void)
>  {
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 410361f41e38..cad5736026d5 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -314,8 +314,7 @@ void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc)
>  	addr = hyp_alloc_pages(&vm->pool, 0);
>  	while (addr) {
>  		memset(hyp_virt_to_page(addr), 0, sizeof(struct hyp_page));
> -		push_hyp_memcache(mc, addr, hyp_virt_to_phys);
> -		WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(addr), 1));
> +		pkvm_teardown_donated_memory(mc, addr, 0);
>  		addr = hyp_alloc_pages(&vm->pool, 0);
>  	}
>  }
> diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> index a3711979bbd3..c51a8a592849 100644
> --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
> +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
> @@ -602,27 +602,28 @@ void *pkvm_map_donated_memory(unsigned long host_va, size_t size)
>  	return va;
>  }
>  
> -static void __unmap_donated_memory(void *va, size_t size)
> +void pkvm_teardown_donated_memory(struct kvm_hyp_memcache *mc, void *va,
> +				  size_t dirty_size)
>  {
> -	WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(va),
> -				       PAGE_ALIGN(size) >> PAGE_SHIFT));
> -}
> +	size_t size = max(PAGE_ALIGN(dirty_size), PAGE_SIZE);
>  
> -void pkvm_unmap_donated_memory(void *va, size_t size)
> -{
>  	if (!va)
>  		return;
>  
> -	memset(va, 0, size);
> -	__unmap_donated_memory(va, size);
> +	memset(va, 0, dirty_size);
> +
> +	if (mc) {
> +		for (void *start = va; start < va + size; start += PAGE_SIZE)
> +			push_hyp_memcache(mc, start, hyp_virt_to_phys);
> +	}
> +
> +	WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(va),
> +				       size >> PAGE_SHIFT));
>  }
>  
> -static void unmap_donated_memory_noclear(void *va, size_t size)
> +void pkvm_unmap_donated_memory(void *va, size_t size)
>  {
> -	if (!va)
> -		return;
> -
> -	__unmap_donated_memory(va, size);
> +	pkvm_teardown_donated_memory(NULL, va, size);
>  }
>  
>  /*
> @@ -759,18 +760,6 @@ int __pkvm_init_vcpu(pkvm_handle_t handle, struct kvm_vcpu *host_vcpu,
>  	return ret;
>  }
>  
> -static void
> -teardown_donated_memory(struct kvm_hyp_memcache *mc, void *addr, size_t size)
> -{
> -	size = PAGE_ALIGN(size);
> -	memset(addr, 0, size);
> -
> -	for (void *start = addr; start < addr + size; start += PAGE_SIZE)
> -		push_hyp_memcache(mc, start, hyp_virt_to_phys);
> -
> -	unmap_donated_memory_noclear(addr, size);
> -}
> -
>  int __pkvm_teardown_vm(pkvm_handle_t handle)
>  {
>  	size_t vm_size, last_ran_size;
> @@ -813,19 +802,18 @@ int __pkvm_teardown_vm(pkvm_handle_t handle)
>  		vcpu_mc = &hyp_vcpu->vcpu.arch.pkvm_memcache;
>  		while (vcpu_mc->nr_pages) {
>  			addr = pop_hyp_memcache(vcpu_mc, hyp_phys_to_virt);
> -			push_hyp_memcache(mc, addr, hyp_virt_to_phys);
> -			unmap_donated_memory_noclear(addr, PAGE_SIZE);
> +			pkvm_teardown_donated_memory(mc, addr, 0);

Here we probably need to pass PAGE_SIZE as an argument instead of "0"
to make sure that we clear out the content of the page before tearing it
down.

>  		}
>  
> -		teardown_donated_memory(mc, hyp_vcpu, sizeof(*hyp_vcpu));
> +		pkvm_teardown_donated_memory(mc, hyp_vcpu, sizeof(*hyp_vcpu));
>  	}
>  
>  	last_ran_size = pkvm_get_last_ran_size();
> -	teardown_donated_memory(mc, hyp_vm->kvm.arch.mmu.last_vcpu_ran,
> -				last_ran_size);
> +	pkvm_teardown_donated_memory(mc, hyp_vm->kvm.arch.mmu.last_vcpu_ran,
> +				     last_ran_size);
>  
>  	vm_size = pkvm_get_hyp_vm_size(hyp_vm->kvm.created_vcpus);
> -	teardown_donated_memory(mc, hyp_vm, vm_size);
> +	pkvm_teardown_donated_memory(mc, hyp_vm, vm_size);
>  	hyp_unpin_shared_mem(host_kvm, host_kvm + 1);
>  	return 0;
>  
> -- 
> 2.39.0
>

Thanks,
Seb

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