Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
On Tue, 27 Jul 2021 19:10:45 +0100,
Will Deacon wrote:
>
> On Thu, Jul 15, 2021 at 05:31:45PM +0100, Marc Zyngier wrote:
> > Make sure we don't issue CMOs when mapping something that
> > is not a memory address in the S2 page tables.
> >
> > Signed-off-by: Marc Zyngier
> > ---
> > arch/arm64/kvm/hyp/pgtable.c | 16 ++--
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index 05321f4165e3..a5874ebd0354 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64
> > end, u32 level,
> > }
> >
> > /* Perform CMOs before installation of the guest stage-2 PTE */
> > - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> > - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> > - granule);
> > -
> > - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > - mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> > + if (kvm_phys_is_valid(phys)) {
> > + if (mm_ops->dcache_clean_inval_poc &&
> > + stage2_pte_cacheable(pgt, new))
> > + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
> > + mm_ops),
> > + granule);
> > + if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > + mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
> > +granule);
> > + }
>
> Given that this check corresponds to checking the validity of 'new', I
> wonder whether we'd be better off pushing the validity checks down into
> stage2_pte_{cacheable,executable}()?
>
> I.e. have stage2_pte_cacheable() return false if !kvm_pte_valid()
That would work just as well. I'll update the patch.
Thanks,
M.
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Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
On Thu, Jul 15, 2021 at 05:31:45PM +0100, Marc Zyngier wrote:
> Make sure we don't issue CMOs when mapping something that
> is not a memory address in the S2 page tables.
>
> Signed-off-by: Marc Zyngier
> ---
> arch/arm64/kvm/hyp/pgtable.c | 16 ++--
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 05321f4165e3..a5874ebd0354 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64
> end, u32 level,
> }
>
> /* Perform CMOs before installation of the guest stage-2 PTE */
> - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> - granule);
> -
> - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> - mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> + if (kvm_phys_is_valid(phys)) {
> + if (mm_ops->dcache_clean_inval_poc &&
> + stage2_pte_cacheable(pgt, new))
> + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
> + mm_ops),
> +granule);
> + if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> + mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
> + granule);
> + }
Given that this check corresponds to checking the validity of 'new', I
wonder whether we'd be better off pushing the validity checks down into
stage2_pte_{cacheable,executable}()?
I.e. have stage2_pte_cacheable() return false if !kvm_pte_valid()
Will
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Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
On Mon, 19 Jul 2021 18:18:02 +0100,
Quentin Perret wrote:
>
> On Thursday 15 Jul 2021 at 17:31:45 (+0100), Marc Zyngier wrote:
> > Make sure we don't issue CMOs when mapping something that
> > is not a memory address in the S2 page tables.
> >
> > Signed-off-by: Marc Zyngier
> > ---
> > arch/arm64/kvm/hyp/pgtable.c | 16 ++--
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index 05321f4165e3..a5874ebd0354 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64
> > end, u32 level,
> > }
> >
> > /* Perform CMOs before installation of the guest stage-2 PTE */
> > - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> > - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> > - granule);
> > -
> > - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > - mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> > + if (kvm_phys_is_valid(phys)) {
> > + if (mm_ops->dcache_clean_inval_poc &&
> > + stage2_pte_cacheable(pgt, new))
> > + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
> > + mm_ops),
> > + granule);
> > + if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> > + mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
> > +granule);
> > + }
>
> Hrmpf so this makes me realize we have a problem here, not really caused
> by your patch though.
>
> Specifically, calling kvm_pgtable_stage2_set_owner() can lead to
> overriding valid mappings with invalid mappings, which is effectively an
> unmap operation. In this case we should issue CMOs when unmapping a
> cacheable page to ensure it is clean to the PoC, like the
> kvm_pgtable_stage2_unmap() does.
You only need that if you to have a non-cacheable mapping to the same
page. Otherwise, you will be fine.
For pages that are moved from host-EL1 to EL2, we're good (I don't
think we ever have a non-cachable mapping at EL2). However, once we
start moving pages to guests, we'll need something.
> Note that you patch is already an improvement over the current state of
> things, because calling stage2_pte_cacheable(pgt, new),
> kvm_pte_follow(new, mm_ops) and friends is bogus when 'new' is invalid
Yeah, I had it mentally earmarked as a potential stable candidate. We
may have to do a bit better in the light of the above though.
Thanks,
M.
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Re: [PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
On Thursday 15 Jul 2021 at 17:31:45 (+0100), Marc Zyngier wrote:
> Make sure we don't issue CMOs when mapping something that
> is not a memory address in the S2 page tables.
>
> Signed-off-by: Marc Zyngier
> ---
> arch/arm64/kvm/hyp/pgtable.c | 16 ++--
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 05321f4165e3..a5874ebd0354 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64
> end, u32 level,
> }
>
> /* Perform CMOs before installation of the guest stage-2 PTE */
> - if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
> - mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
> - granule);
> -
> - if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> - mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
> + if (kvm_phys_is_valid(phys)) {
> + if (mm_ops->dcache_clean_inval_poc &&
> + stage2_pte_cacheable(pgt, new))
> + mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
> + mm_ops),
> +granule);
> + if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
> + mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
> + granule);
> + }
Hrmpf so this makes me realize we have a problem here, not really caused
by your patch though.
Specifically, calling kvm_pgtable_stage2_set_owner() can lead to
overriding valid mappings with invalid mappings, which is effectively an
unmap operation. In this case we should issue CMOs when unmapping a
cacheable page to ensure it is clean to the PoC, like the
kvm_pgtable_stage2_unmap() does.
Note that you patch is already an improvement over the current state of
things, because calling stage2_pte_cacheable(pgt, new),
kvm_pte_follow(new, mm_ops) and friends is bogus when 'new' is invalid
...
Thanks,
Quentin
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[PATCH 02/16] KVM: arm64: Don't issue CMOs when the physical address is invalid
Make sure we don't issue CMOs when mapping something that
is not a memory address in the S2 page tables.
Signed-off-by: Marc Zyngier
---
arch/arm64/kvm/hyp/pgtable.c | 16 ++--
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 05321f4165e3..a5874ebd0354 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -619,12 +619,16 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end,
u32 level,
}
/* Perform CMOs before installation of the guest stage-2 PTE */
- if (mm_ops->dcache_clean_inval_poc && stage2_pte_cacheable(pgt, new))
- mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new, mm_ops),
- granule);
-
- if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
- mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops), granule);
+ if (kvm_phys_is_valid(phys)) {
+ if (mm_ops->dcache_clean_inval_poc &&
+ stage2_pte_cacheable(pgt, new))
+ mm_ops->dcache_clean_inval_poc(kvm_pte_follow(new,
+ mm_ops),
+ granule);
+ if (mm_ops->icache_inval_pou && stage2_pte_executable(new))
+ mm_ops->icache_inval_pou(kvm_pte_follow(new, mm_ops),
+granule);
+ }
smp_store_release(ptep, new);
if (stage2_pte_is_counted(new))
--
2.30.2
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