On Thu, Jan 24, 2013 at 12:13 PM, Catalin Marinas <[email protected]> wrote: > On Thu, Jan 24, 2013 at 05:04:32PM +0000, Christoffer Dall wrote: >> On Thu, Jan 24, 2013 at 12:02 PM, Catalin Marinas >> <[email protected]> wrote: >> > On Thu, Jan 24, 2013 at 04:05:33PM +0000, Christoffer Dall wrote: >> >> On Thu, Jan 24, 2013 at 6:39 AM, Catalin Marinas >> >> <[email protected]> wrote: >> >> > On Wed, Jan 16, 2013 at 05:57:26PM +0000, Christoffer Dall wrote: >> >> >> @@ -82,6 +85,10 @@ extern pgprot_t pgprot_kernel; >> >> >> #define PAGE_READONLY_EXEC _MOD_PROT(pgprot_user, L_PTE_USER | >> >> >> L_PTE_RDONLY) >> >> >> #define PAGE_KERNEL _MOD_PROT(pgprot_kernel, L_PTE_XN) >> >> >> #define PAGE_KERNEL_EXEC pgprot_kernel >> >> >> +#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_USER | L_PTE_S2_RDONLY) >> >> > >> >> > Are these S2 read-only by default? >> >> >> >> not sure I understand what you're asking here? >> > >> > Why do you pass L_PTE_S2_RDONLY? Do you need to restrict guest writes >> > via the stage 2 attributes? >> > >> yes, for example when KSM merges two pages, then it must be mapped >> read-only to the guest so that we catch writes and perform COW. > > OK, so you want the default to be read-only unless write access is > required and you perform an 'or' with L_PTE_S2_RDWR. Sounds fine. > exactly, the specific pointer to the code is in line ~562 in arch/arm/kvm/mmu.c.
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