From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Sat, 13 Sep 2014 11:41:35 +0100 Subject: [PATCH 1/2] ARM: kvm: define =?UTF-8?Q?PAGE=5FS=32=5FDEVICE?= =?UTF-8?Q?=20as=20read-only=20by=20default?= In-Reply-To: <1410603462-28900-1-git-send-email-ard.biesheuvel@linaro.org> References: <1410603462-28900-1-git-send-email-ard.biesheuvel@linaro.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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 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.