From: marc.zyngier@arm.com (Marc Zyngier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] ARM: kvm: define PAGE_S2_DEVICE as read-only by default
Date: Sat, 13 Sep 2014 11:41:35 +0100 [thread overview]
Message-ID: <bcbc1c52f9e1eeb24f0bd1956236f0a3@www.loen.fr> (raw)
In-Reply-To: <1410603462-28900-1-git-send-email-ard.biesheuvel@linaro.org>
Hi Ard,
On 2014-09-13 11:17, Ard Biesheuvel wrote:
> Now that we support read-only memslots, we need to make sure that
> pass-through device mappings are not mapped writable if the guest
> has requested them to be read-only. The existing implementation
> already honours this by calling kvm_set_s2pte_writable() on the new
> pte in case of writable mappings, so all we need to do is define
> the default pgprot_t value used for devices to be PTE_S2_RDONLY.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
I feel very uncomfortable with this change. Why would we map a device
RO? Is that only for completeness sake?
Note that we also use PAGE_S2_DEVICE for things that are not mapped
through a memslot, such as the GIC.
Thanks,
M.
> ---
> arch/arm/include/asm/pgtable.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/pgtable.h
> b/arch/arm/include/asm/pgtable.h
> index 01baef07cd0c..92b2fbe18868 100644
> --- a/arch/arm/include/asm/pgtable.h
> +++ b/arch/arm/include/asm/pgtable.h
> @@ -100,7 +100,7 @@ extern pgprot_t pgprot_s2_device;
> #define PAGE_HYP _MOD_PROT(pgprot_kernel, L_PTE_HYP)
> #define PAGE_HYP_DEVICE _MOD_PROT(pgprot_hyp_device, L_PTE_HYP)
> #define PAGE_S2 _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY)
> -#define PAGE_S2_DEVICE _MOD_PROT(pgprot_s2_device, L_PTE_S2_RDWR)
> +#define PAGE_S2_DEVICE _MOD_PROT(pgprot_s2_device, L_PTE_S2_RDONLY)
>
> #define __PAGE_NONE __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY |
> L_PTE_XN | L_PTE_NONE)
> #define __PAGE_SHARED __pgprot(_L_PTE_DEFAULT | L_PTE_USER |
> L_PTE_XN)
--
Fast, cheap, reliable. Pick two.
next prev parent reply other threads:[~2014-09-13 10:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-13 10:17 [PATCH 1/2] ARM: kvm: define PAGE_S2_DEVICE as read-only by default Ard Biesheuvel
2014-09-13 10:17 ` [PATCH 2/2] arm64: " Ard Biesheuvel
2014-09-13 10:41 ` Marc Zyngier [this message]
2014-09-13 11:15 ` [PATCH 1/2] ARM: " Ard Biesheuvel
2014-09-13 17:06 ` Christoffer Dall
2014-09-14 4:49 ` Ard Biesheuvel
2014-09-14 9:09 ` Marc Zyngier
2014-09-14 9:43 ` Ard Biesheuvel
2014-09-14 22:57 ` Ard Biesheuvel
2014-09-15 3:37 ` Peter Maydell
2014-09-15 19:41 ` Mario Smarduch
2014-09-15 19:45 ` Peter Maydell
2014-09-17 19:19 ` Mario Smarduch
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