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From: Quentin Perret <qperret@google.com>
To: Fuad Tabba <tabba@google.com>
Cc: maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
	suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
	ardb@kernel.org, qwandor@google.com, dbrazdil@google.com,
	kernel-team@android.com
Subject: Re: [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode
Date: Tue, 3 Aug 2021 11:43:26 +0100	[thread overview]
Message-ID: <YQkdztIHwXfj7Sbc@google.com> (raw)
In-Reply-To: <CA+EHjTw7W=5JqH+oZAqLPrf_6222eazDnSk24h4EuGE1VLwKYg@mail.gmail.com>

On Tuesday 03 Aug 2021 at 10:22:03 (+0200), Fuad Tabba wrote:
> Hi Quentin,
> 
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > index 0ccea58df7e0..1b67f562b6fc 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > @@ -338,6 +338,95 @@ static int host_stage2_idmap(u64 addr)
> >         return ret;
> >  }
> >
> > +static inline bool check_prot(enum kvm_pgtable_prot prot,
> > +                             enum kvm_pgtable_prot required,
> > +                             enum kvm_pgtable_prot denied)
> > +{
> > +       return (prot & (required | denied)) == required;
> > +}
> > +
> > +int __pkvm_host_share_hyp(u64 pfn)
> > +{
> > +       phys_addr_t addr = hyp_pfn_to_phys(pfn);
> > +       enum kvm_pgtable_prot prot, cur;
> > +       void *virt = __hyp_va(addr);
> > +       enum pkvm_page_state state;
> > +       kvm_pte_t pte;
> > +       u32 level;
> > +       int ret;
> > +
> > +       if (!range_is_memory(addr, addr + PAGE_SIZE))
> > +               return -EINVAL;
> > +
> > +       hyp_spin_lock(&host_kvm.lock);
> > +       hyp_spin_lock(&pkvm_pgd_lock);
> > +
> > +       ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +       if (!pte)
> > +               goto map_shared;
> 
> Should this check whether kvm_pte_valid as well, is that guaranteed to
> always be the case, or implicitly handled later?

Yep, this is implicitly handled by kvm_pgtable_stage2_pte_prot() which
is guaranteed not to return KVM_PGTABLE_PROT_RWX for an invalid mapping.

> > +
> > +       /*
> > +        * Check attributes in the host stage-2 PTE. We need the page to be:
> > +        *  - mapped RWX as we're sharing memory;
> > +        *  - not borrowed, as that implies absence of ownership.
> > +        * Otherwise, we can't let it got through
> > +        */
> > +       cur = kvm_pgtable_stage2_pte_prot(pte);
> > +       prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, KVM_PGTABLE_PROT_RWX, prot)) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       state = pkvm_getstate(cur);
> > +       if (state == PKVM_PAGE_OWNED)
> > +               goto map_shared;
> > +
> > +       /*
> > +        * Tolerate double-sharing the same page, but this requires
> > +        * cross-checking the hypervisor stage-1.
> > +        */
> > +       if (state != PKVM_PAGE_SHARED_OWNED) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +
> > +       /*
> > +        * If the page has been shared with the hypervisor, it must be
> > +        * SHARED_BORROWED already.
> > +        */
> 
> This comment confused me at first, but then I realized it's referring
> to the page from the hyp's point of view. Could you add something to
> the comment to that effect?

Sure thing.

> It might also make it easier to follow if the variables could be
> annotated to specify whether cur, state, and prot are the host's or
> hyps (and not reuse the same one for both).
> 
> > +       cur = kvm_pgtable_hyp_pte_prot(pte);
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, prot, ~prot))
> > +               ret = EPERM;
> > +       goto unlock;
> > +
> > +map_shared:
> > +       /*
> > +        * If the page is not yet shared, adjust mappings in both page-tables
> > +        * while both locks are held.
> > +        */
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +       prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED);
> > +       ret = host_stage2_idmap_locked(addr, addr + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +unlock:
> > +       hyp_spin_unlock(&pkvm_pgd_lock);
> > +       hyp_spin_unlock(&host_kvm.lock);
> > +
> > +       return ret;
> > +}
> > +
> >  void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
> >  {
> >         struct kvm_vcpu_fault_info fault;
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 0625bf2353c2..cbab146cda6a 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size,
> >  {
> >         int err;
> >
> > -       if (!kvm_host_owns_hyp_mappings()) {
> > -               return kvm_call_hyp_nvhe(__pkvm_create_mappings,
> > -                                        start, size, phys, prot);
> > -       }
> > +       if (WARN_ON(!kvm_host_owns_hyp_mappings()))
> > +               return -EINVAL;
> >
> >         mutex_lock(&kvm_hyp_pgd_mutex);
> >         err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
> > @@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
> >         }
> >  }
> >
> > +static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
> > +{
> > +       phys_addr_t addr;
> > +       int ret;
> > +
> > +       for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
> > +               ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
> > +                                       __phys_to_pfn(addr));
> 
> I guess we don't expect this to happen often, but I wonder if it would
> be better to have the looping in the hyp call rather than here, to
> reduce the number of hyp calls when sharing.

Yes, I was wondering the same thing, but ended up doing the looping here
to avoid spending long periods of time in a non-preemptible state at
EL2. Probably doesn't make a big difference for now, but it might if we
ever need to share large memory regions.

Cheers,
Quentin

> 
> Thanks,
> /fuad
> 
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  /**
> >   * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
> >   * @from:      The virtual kernel start address of the range
> > @@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> >         if (is_kernel_in_hyp_mode())
> >                 return 0;
> >
> > +       if (!kvm_host_owns_hyp_mappings()) {
> > +               if (WARN_ON(prot != PAGE_HYP))
> > +                       return -EPERM;
> > +               return pkvm_share_hyp(kvm_kaddr_to_phys(from),
> > +                                     kvm_kaddr_to_phys(to));
> > +       }
> > +
> >         start = start & PAGE_MASK;
> >         end = PAGE_ALIGN(end);
> >
> > --
> > 2.32.0.432.gabb21c7263-goog
> >

WARNING: multiple messages have this Message-ID
From: Quentin Perret <qperret@google.com>
To: Fuad Tabba <tabba@google.com>
Cc: kernel-team@android.com, qwandor@google.com, maz@kernel.org,
	linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
	will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode
Date: Tue, 3 Aug 2021 11:43:26 +0100	[thread overview]
Message-ID: <YQkdztIHwXfj7Sbc@google.com> (raw)
In-Reply-To: <CA+EHjTw7W=5JqH+oZAqLPrf_6222eazDnSk24h4EuGE1VLwKYg@mail.gmail.com>

On Tuesday 03 Aug 2021 at 10:22:03 (+0200), Fuad Tabba wrote:
> Hi Quentin,
> 
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > index 0ccea58df7e0..1b67f562b6fc 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > @@ -338,6 +338,95 @@ static int host_stage2_idmap(u64 addr)
> >         return ret;
> >  }
> >
> > +static inline bool check_prot(enum kvm_pgtable_prot prot,
> > +                             enum kvm_pgtable_prot required,
> > +                             enum kvm_pgtable_prot denied)
> > +{
> > +       return (prot & (required | denied)) == required;
> > +}
> > +
> > +int __pkvm_host_share_hyp(u64 pfn)
> > +{
> > +       phys_addr_t addr = hyp_pfn_to_phys(pfn);
> > +       enum kvm_pgtable_prot prot, cur;
> > +       void *virt = __hyp_va(addr);
> > +       enum pkvm_page_state state;
> > +       kvm_pte_t pte;
> > +       u32 level;
> > +       int ret;
> > +
> > +       if (!range_is_memory(addr, addr + PAGE_SIZE))
> > +               return -EINVAL;
> > +
> > +       hyp_spin_lock(&host_kvm.lock);
> > +       hyp_spin_lock(&pkvm_pgd_lock);
> > +
> > +       ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +       if (!pte)
> > +               goto map_shared;
> 
> Should this check whether kvm_pte_valid as well, is that guaranteed to
> always be the case, or implicitly handled later?

Yep, this is implicitly handled by kvm_pgtable_stage2_pte_prot() which
is guaranteed not to return KVM_PGTABLE_PROT_RWX for an invalid mapping.

> > +
> > +       /*
> > +        * Check attributes in the host stage-2 PTE. We need the page to be:
> > +        *  - mapped RWX as we're sharing memory;
> > +        *  - not borrowed, as that implies absence of ownership.
> > +        * Otherwise, we can't let it got through
> > +        */
> > +       cur = kvm_pgtable_stage2_pte_prot(pte);
> > +       prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, KVM_PGTABLE_PROT_RWX, prot)) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       state = pkvm_getstate(cur);
> > +       if (state == PKVM_PAGE_OWNED)
> > +               goto map_shared;
> > +
> > +       /*
> > +        * Tolerate double-sharing the same page, but this requires
> > +        * cross-checking the hypervisor stage-1.
> > +        */
> > +       if (state != PKVM_PAGE_SHARED_OWNED) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +
> > +       /*
> > +        * If the page has been shared with the hypervisor, it must be
> > +        * SHARED_BORROWED already.
> > +        */
> 
> This comment confused me at first, but then I realized it's referring
> to the page from the hyp's point of view. Could you add something to
> the comment to that effect?

Sure thing.

> It might also make it easier to follow if the variables could be
> annotated to specify whether cur, state, and prot are the host's or
> hyps (and not reuse the same one for both).
> 
> > +       cur = kvm_pgtable_hyp_pte_prot(pte);
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, prot, ~prot))
> > +               ret = EPERM;
> > +       goto unlock;
> > +
> > +map_shared:
> > +       /*
> > +        * If the page is not yet shared, adjust mappings in both page-tables
> > +        * while both locks are held.
> > +        */
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +       prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED);
> > +       ret = host_stage2_idmap_locked(addr, addr + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +unlock:
> > +       hyp_spin_unlock(&pkvm_pgd_lock);
> > +       hyp_spin_unlock(&host_kvm.lock);
> > +
> > +       return ret;
> > +}
> > +
> >  void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
> >  {
> >         struct kvm_vcpu_fault_info fault;
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 0625bf2353c2..cbab146cda6a 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size,
> >  {
> >         int err;
> >
> > -       if (!kvm_host_owns_hyp_mappings()) {
> > -               return kvm_call_hyp_nvhe(__pkvm_create_mappings,
> > -                                        start, size, phys, prot);
> > -       }
> > +       if (WARN_ON(!kvm_host_owns_hyp_mappings()))
> > +               return -EINVAL;
> >
> >         mutex_lock(&kvm_hyp_pgd_mutex);
> >         err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
> > @@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
> >         }
> >  }
> >
> > +static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
> > +{
> > +       phys_addr_t addr;
> > +       int ret;
> > +
> > +       for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
> > +               ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
> > +                                       __phys_to_pfn(addr));
> 
> I guess we don't expect this to happen often, but I wonder if it would
> be better to have the looping in the hyp call rather than here, to
> reduce the number of hyp calls when sharing.

Yes, I was wondering the same thing, but ended up doing the looping here
to avoid spending long periods of time in a non-preemptible state at
EL2. Probably doesn't make a big difference for now, but it might if we
ever need to share large memory regions.

Cheers,
Quentin

> 
> Thanks,
> /fuad
> 
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  /**
> >   * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
> >   * @from:      The virtual kernel start address of the range
> > @@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> >         if (is_kernel_in_hyp_mode())
> >                 return 0;
> >
> > +       if (!kvm_host_owns_hyp_mappings()) {
> > +               if (WARN_ON(prot != PAGE_HYP))
> > +                       return -EPERM;
> > +               return pkvm_share_hyp(kvm_kaddr_to_phys(from),
> > +                                     kvm_kaddr_to_phys(to));
> > +       }
> > +
> >         start = start & PAGE_MASK;
> >         end = PAGE_ALIGN(end);
> >
> > --
> > 2.32.0.432.gabb21c7263-goog
> >
_______________________________________________
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kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID
From: Quentin Perret <qperret@google.com>
To: Fuad Tabba <tabba@google.com>
Cc: maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
	suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
	ardb@kernel.org, qwandor@google.com, dbrazdil@google.com,
	kernel-team@android.com
Subject: Re: [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode
Date: Tue, 3 Aug 2021 11:43:26 +0100	[thread overview]
Message-ID: <YQkdztIHwXfj7Sbc@google.com> (raw)
In-Reply-To: <CA+EHjTw7W=5JqH+oZAqLPrf_6222eazDnSk24h4EuGE1VLwKYg@mail.gmail.com>

On Tuesday 03 Aug 2021 at 10:22:03 (+0200), Fuad Tabba wrote:
> Hi Quentin,
> 
> > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > index 0ccea58df7e0..1b67f562b6fc 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> > @@ -338,6 +338,95 @@ static int host_stage2_idmap(u64 addr)
> >         return ret;
> >  }
> >
> > +static inline bool check_prot(enum kvm_pgtable_prot prot,
> > +                             enum kvm_pgtable_prot required,
> > +                             enum kvm_pgtable_prot denied)
> > +{
> > +       return (prot & (required | denied)) == required;
> > +}
> > +
> > +int __pkvm_host_share_hyp(u64 pfn)
> > +{
> > +       phys_addr_t addr = hyp_pfn_to_phys(pfn);
> > +       enum kvm_pgtable_prot prot, cur;
> > +       void *virt = __hyp_va(addr);
> > +       enum pkvm_page_state state;
> > +       kvm_pte_t pte;
> > +       u32 level;
> > +       int ret;
> > +
> > +       if (!range_is_memory(addr, addr + PAGE_SIZE))
> > +               return -EINVAL;
> > +
> > +       hyp_spin_lock(&host_kvm.lock);
> > +       hyp_spin_lock(&pkvm_pgd_lock);
> > +
> > +       ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +       if (!pte)
> > +               goto map_shared;
> 
> Should this check whether kvm_pte_valid as well, is that guaranteed to
> always be the case, or implicitly handled later?

Yep, this is implicitly handled by kvm_pgtable_stage2_pte_prot() which
is guaranteed not to return KVM_PGTABLE_PROT_RWX for an invalid mapping.

> > +
> > +       /*
> > +        * Check attributes in the host stage-2 PTE. We need the page to be:
> > +        *  - mapped RWX as we're sharing memory;
> > +        *  - not borrowed, as that implies absence of ownership.
> > +        * Otherwise, we can't let it got through
> > +        */
> > +       cur = kvm_pgtable_stage2_pte_prot(pte);
> > +       prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, KVM_PGTABLE_PROT_RWX, prot)) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       state = pkvm_getstate(cur);
> > +       if (state == PKVM_PAGE_OWNED)
> > +               goto map_shared;
> > +
> > +       /*
> > +        * Tolerate double-sharing the same page, but this requires
> > +        * cross-checking the hypervisor stage-1.
> > +        */
> > +       if (state != PKVM_PAGE_SHARED_OWNED) {
> > +               ret = -EPERM;
> > +               goto unlock;
> > +       }
> > +
> > +       ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, &level);
> > +       if (ret)
> > +               goto unlock;
> > +
> > +       /*
> > +        * If the page has been shared with the hypervisor, it must be
> > +        * SHARED_BORROWED already.
> > +        */
> 
> This comment confused me at first, but then I realized it's referring
> to the page from the hyp's point of view. Could you add something to
> the comment to that effect?

Sure thing.

> It might also make it easier to follow if the variables could be
> annotated to specify whether cur, state, and prot are the host's or
> hyps (and not reuse the same one for both).
> 
> > +       cur = kvm_pgtable_hyp_pte_prot(pte);
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       if (!check_prot(cur, prot, ~prot))
> > +               ret = EPERM;
> > +       goto unlock;
> > +
> > +map_shared:
> > +       /*
> > +        * If the page is not yet shared, adjust mappings in both page-tables
> > +        * while both locks are held.
> > +        */
> > +       prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
> > +       ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +       prot = pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED);
> > +       ret = host_stage2_idmap_locked(addr, addr + PAGE_SIZE, prot);
> > +       BUG_ON(ret);
> > +
> > +unlock:
> > +       hyp_spin_unlock(&pkvm_pgd_lock);
> > +       hyp_spin_unlock(&host_kvm.lock);
> > +
> > +       return ret;
> > +}
> > +
> >  void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
> >  {
> >         struct kvm_vcpu_fault_info fault;
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 0625bf2353c2..cbab146cda6a 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -259,10 +259,8 @@ static int __create_hyp_mappings(unsigned long start, unsigned long size,
> >  {
> >         int err;
> >
> > -       if (!kvm_host_owns_hyp_mappings()) {
> > -               return kvm_call_hyp_nvhe(__pkvm_create_mappings,
> > -                                        start, size, phys, prot);
> > -       }
> > +       if (WARN_ON(!kvm_host_owns_hyp_mappings()))
> > +               return -EINVAL;
> >
> >         mutex_lock(&kvm_hyp_pgd_mutex);
> >         err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
> > @@ -282,6 +280,21 @@ static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
> >         }
> >  }
> >
> > +static int pkvm_share_hyp(phys_addr_t start, phys_addr_t end)
> > +{
> > +       phys_addr_t addr;
> > +       int ret;
> > +
> > +       for (addr = ALIGN_DOWN(start, PAGE_SIZE); addr < end; addr += PAGE_SIZE) {
> > +               ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp,
> > +                                       __phys_to_pfn(addr));
> 
> I guess we don't expect this to happen often, but I wonder if it would
> be better to have the looping in the hyp call rather than here, to
> reduce the number of hyp calls when sharing.

Yes, I was wondering the same thing, but ended up doing the looping here
to avoid spending long periods of time in a non-preemptible state at
EL2. Probably doesn't make a big difference for now, but it might if we
ever need to share large memory regions.

Cheers,
Quentin

> 
> Thanks,
> /fuad
> 
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  /**
> >   * create_hyp_mappings - duplicate a kernel virtual address range in Hyp mode
> >   * @from:      The virtual kernel start address of the range
> > @@ -302,6 +315,13 @@ int create_hyp_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
> >         if (is_kernel_in_hyp_mode())
> >                 return 0;
> >
> > +       if (!kvm_host_owns_hyp_mappings()) {
> > +               if (WARN_ON(prot != PAGE_HYP))
> > +                       return -EPERM;
> > +               return pkvm_share_hyp(kvm_kaddr_to_phys(from),
> > +                                     kvm_kaddr_to_phys(to));
> > +       }
> > +
> >         start = start & PAGE_MASK;
> >         end = PAGE_ALIGN(end);
> >
> > --
> > 2.32.0.432.gabb21c7263-goog
> >

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  reply	other threads:[~2021-08-03 10:43 UTC|newest]

Thread overview: 135+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 13:27 [PATCH v3 00/21] Track shared pages at EL2 " Quentin Perret
2021-07-29 13:27 ` Quentin Perret
2021-07-29 13:27 ` Quentin Perret
2021-07-29 13:27 ` [PATCH v3 01/21] KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at EL2 Quentin Perret
2021-07-29 13:27   ` Quentin Perret
2021-07-29 13:27   ` Quentin Perret
2021-07-29 13:27 ` [PATCH v3 02/21] KVM: arm64: Introduce hyp_assert_lock_held() Quentin Perret
2021-07-29 13:27   ` Quentin Perret
2021-07-29 13:27   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 03/21] KVM: arm64: Provide the host_stage2_try() helper macro Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:36   ` Fuad Tabba
2021-08-02  9:36     ` Fuad Tabba
2021-08-02  9:36     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 04/21] KVM: arm64: Introduce helper to retrieve a PTE and its level Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 05/21] KVM: arm64: Expose page-table helpers Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 06/21] KVM: arm64: Optimize host memory aborts Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:37   ` Fuad Tabba
2021-08-02  9:37     ` Fuad Tabba
2021-08-02  9:37     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 07/21] KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:37   ` Fuad Tabba
2021-08-02  9:37     ` Fuad Tabba
2021-08-02  9:37     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 08/21] KVM: arm64: Don't overwrite software bits with owner id Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:38   ` Fuad Tabba
2021-08-02  9:38     ` Fuad Tabba
2021-08-02  9:38     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 09/21] KVM: arm64: Tolerate re-creating hyp mappings to set software bits Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:50   ` Fuad Tabba
2021-08-02  9:50     ` Fuad Tabba
2021-08-02  9:50     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 10/21] KVM: arm64: Enable forcing page-level stage-2 mappings Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02  9:49   ` Fuad Tabba
2021-08-02  9:49     ` Fuad Tabba
2021-08-02  9:49     ` Fuad Tabba
2021-08-03 10:13     ` Quentin Perret
2021-08-03 10:13       ` Quentin Perret
2021-08-03 10:13       ` Quentin Perret
2021-08-03 10:43       ` Fuad Tabba
2021-08-03 10:43         ` Fuad Tabba
2021-08-03 10:43         ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 11/21] KVM: arm64: Allow populating software bits Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 12/21] KVM: arm64: Add helpers to tag shared pages in SW bits Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02 10:30   ` Fuad Tabba
2021-08-02 10:30     ` Fuad Tabba
2021-08-02 10:30     ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 13/21] KVM: arm64: Expose host stage-2 manipulation helpers Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02 11:13   ` Fuad Tabba
2021-08-02 11:13     ` Fuad Tabba
2021-08-02 11:13     ` Fuad Tabba
2021-08-03 10:20     ` Quentin Perret
2021-08-03 10:20       ` Quentin Perret
2021-08-03 10:20       ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 14/21] KVM: arm64: Expose pkvm_hyp_id Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 15/21] KVM: arm64: Introduce addr_is_memory() Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02 14:52   ` Fuad Tabba
2021-08-02 14:52     ` Fuad Tabba
2021-08-02 14:52     ` Fuad Tabba
2021-08-03 10:23     ` Quentin Perret
2021-08-03 10:23       ` Quentin Perret
2021-08-03 10:23       ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 16/21] KVM: arm64: Enable retrieving protections attributes of PTEs Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-02 14:52   ` Fuad Tabba
2021-08-02 14:52     ` Fuad Tabba
2021-08-02 14:52     ` Fuad Tabba
2021-08-03 10:24     ` Quentin Perret
2021-08-03 10:24       ` Quentin Perret
2021-08-03 10:24       ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 17/21] KVM: arm64: Mark host bss and rodata section as shared Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-03  5:02   ` Fuad Tabba
2021-08-03  5:02     ` Fuad Tabba
2021-08-03  5:02     ` Fuad Tabba
2021-08-03 10:34     ` Quentin Perret
2021-08-03 10:34       ` Quentin Perret
2021-08-03 10:34       ` Quentin Perret
2021-08-03 10:54       ` Fuad Tabba
2021-08-03 10:54         ` Fuad Tabba
2021-08-03 10:54         ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 18/21] KVM: arm64: Remove __pkvm_mark_hyp Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 19/21] KVM: arm64: Refactor protected nVHE stage-1 locking Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-03  5:31   ` Fuad Tabba
2021-08-03  5:31     ` Fuad Tabba
2021-08-03  5:31     ` Fuad Tabba
2021-08-03 10:37     ` Quentin Perret
2021-08-03 10:37       ` Quentin Perret
2021-08-03 10:37       ` Quentin Perret
2021-08-03 10:51       ` Fuad Tabba
2021-08-03 10:51         ` Fuad Tabba
2021-08-03 10:51         ` Fuad Tabba
2021-07-29 13:28 ` [PATCH v3 20/21] KVM: arm64: Restrict EL2 stage-1 changes in protected mode Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-08-03  8:22   ` Fuad Tabba
2021-08-03  8:22     ` Fuad Tabba
2021-08-03  8:22     ` Fuad Tabba
2021-08-03 10:43     ` Quentin Perret [this message]
2021-08-03 10:43       ` Quentin Perret
2021-08-03 10:43       ` Quentin Perret
2021-07-29 13:28 ` [PATCH v3 21/21] KVM: arm64: Make __pkvm_create_mappings static Quentin Perret
2021-07-29 13:28   ` Quentin Perret
2021-07-29 13:28   ` Quentin Perret

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